# An Informal look at the Eneloop NC-MQNO5U Charger



## SilverFox (Dec 25, 2007)

I started looking at this charger and ran some tests.

Here is the set up:

Charge in the Eneloop charger and discharge at 0.5 amps on the C-9000.

First run involved charging my Sanyo 2500 mAh cells. I charged them in the Eneloop charger, let them rest for 30 minutes, then discharged them on the C-9000.

The results from charging them on the Eneloop charger are as follows:

2113 mAh
2130
2100
2125

I then charged the same cells on the C-9000 at 1000 mA. Let it top off for 2 hours, rest for 30 minutes, then discharged them on the C-9000 at 0.5 amps.

The results from charging on the C-9000 were:

2303
2279
2299
2266

With 2500 mAh cells, I got a fuller charge on the C-9000.

I then moved on to some Eneloop cells.

The results from charging them in the Eneloop charger:

1890
1918
1928
1893

Once again I charged them in the C-9000 and ended up with:

1891
1926
1926
1899

In this case, both chargers seem to have charged to about the same capacity.

I am going to see what happens when you have 2 cells that are nearly full charging with 2 cells that are less full.

Tom


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## bhds (Dec 25, 2007)

Is this the NC-MQN05U model? Looking forward to your tests if it is.  I've been wondering how it handles charging multiple cells with differing states of discharge.


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## tslrc (Dec 25, 2007)

I was wondering the same....


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## FlashCrazy (Dec 26, 2007)

Hi Tom,
Just wondering why you used a 1000 mA charge rate on the C-9000 instead of the 300 mA rate that the Sanyo charger uses. Also, you let them top off for 2 hours on the C-9000 after termination... did you do the same on the Sanyo, or pluck them right after termination? I guess since the light on the Sanyo doesn't extinguish until the last cell has peaked, the other cells got at least a little trickle charge. 

I figure you must have your reasons.. teach me, wise one. :bow:


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## SilverFox (Dec 26, 2007)

Hello FlashCrazy,

I used the default charging for both chargers.

I believe the Eneloop charger simply shuts off after charging. I did leave it for a while after the light went off, but from the results it appears that it charges then shuts off.

The main reason for using 1000 mA on the C-9000 is that the battery manufacturers (including Sanyo) recommend charging in the 0.5 - 1.0C range. 1000 mA is 0.5C for the Eneloop cells.

Tom


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## SilverFox (Dec 26, 2007)

Update:

I installed two Eneloop cells in the charger and fully charged them. I then stuck two more Eneloop cells in and waited until the light went out. Discharging them on the C-9000 revealed that all 4 cells were completely charged.

I initially used slots 1 and 3, then put cells in 2 and 4.

The discharged values were very similar to what I reported earlier for the Eneloop cells.

I think it is safe to say that this charger has independent charging channels.

Tom


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## dave43 (Dec 26, 2007)

Silverfox,

Thanks for doing the test. It is very helpful. So after the two initial batteries were charged and the light went off...the light came on again when the second set were put in...Correct? Do you think there could be any chance of the original 2 becoming overcharged?


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## SilverFox (Dec 26, 2007)

Hello Dave,

I actually unplugged the unit while I was sticking the second pair of cells in. After they were in, I plugged the unit back in.

I am not sure how this charger terminates the charge, so I don't know if the originally fully charged cells were over charged or not. By the time the other cells were fully charged, the original cells had not heated up, nor were they at a higher voltage. Both of these things indicate that they were not over charged.

Tom


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## Bones (Dec 26, 2007)

SilverFox said:


> I started looking at this charger and ran some tests.
> 
> Here is the set up:
> 
> ...



I've never known the MQN05 to exceed 7 hours during any charge, which makes me wonder if it isn't timing out with cells with a higher capacity than the Eneloop.

Did you happen to notice the duration of the charge with the 2500 mAh cells?


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## SilverFox (Dec 26, 2007)

Hello Bones,

I did not keep track of charging times. Sorry.

Tom


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## FlashCrazy (Dec 27, 2007)

A while back, I put 4 AAA batteries of different states of charge on this charger and probed each with a volt meter. I concluded it was an independent channel charger since the voltage of each battery was quite different throughout the charge. I happened to catch when one of them peaked (well right before anyway), and then after when that particular battery's voltage measured slightly less. The rest continued on with their charge.

I could hear the charger "pulsing" during charge... it was a somewhat high pitched intermittent buzz for a split second, every second or so. I could hear the same sound after the charger's light extinguished, although less frequent. I was pretty sure the charger was trickle charging after termination.

Well, today I tested it using an ammeter. I put one AAA Eneloop in the charger. During charge, the charger pulsed the battery with 610 mA for about a 1/4 second, then rested for 3/4 seconds, then pulsed again, rested, etc. Averaged out, this correlates with the 150 mA charge rated listed on the back of the charger for AAA's. 

When the charger light extinguished, the charger pulsed the battery with anywhere from 10 to 40 mA for about a 1/4 second, then rested for 8 seconds, then repeated. It continued this cycle for one minute, then rested for a full minute. It then pulsed again as before for another minute, then rested a minute. This cycle repeated for as long as I had the battery in place. I took it out after about 20 minutes. I'm not sure one would call this a trickle charge, maybe more of a "maintenance" charge. Pretty cool, nonetheless.


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## SilverFox (Dec 27, 2007)

Hello FlashCrazy,

Interesting...

I suppose the next question is if it every completely stops charging...

However, as you have indicated, the maintenance charge is quite low.

You didn't happen to notice how it terminates the charge did you?

Tom


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## FlashCrazy (Dec 27, 2007)

SilverFox said:


> Hello FlashCrazy,
> 
> Interesting...
> 
> ...


 
I'll have to test again and leave the battery in for a few hours to see if it ever completely shuts off. I didn't notice how it terminates, so maybe on the next test I'll be able to catch the battery peaking.


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## SilverFox (Dec 30, 2007)

Update:

I left the cells in the charger, and the charger plugged in for 3 days. I pulled a cell and it was at 1.45 volts. It appears that this charger does continue to trickle charge.

After a few hours, the cell I pulled was at 1.43 volts and dropping.

Tom


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## SilverFox (Dec 30, 2007)

Update:

This morning I took the cell that I had pulled from the charger and put it back in. The voltage had dropped to 1.42 volts. The light on the charge lit up and it continued to charge the cell for about 4 hours. The cell heated up to around 105 F. The cell next to it heated up a little, and the other two cells remained at room temperature.

Let's see now, this charger charges at 300 mA, I charged my fully charged cell for an additional 4 hours, so I put in an additional 1200 mAh that went to heating the cell up. 

I would classify this as a missed termination.

Tom


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## FlashCrazy (Dec 30, 2007)

I got some time to test the charger a little more the other day. I happened to catch a cell peaking (a AAA). To me, it looked like it was terminating on a 0 Delta V basis, but I guess it'd be really hard to tell with just my DMM. It peaked at 1.565 volts, then the charger light went off. I didn't notice it drop in voltage right before the light went off, but again, I can't be sure with the equipment I was using.

I left the cell on the charger for the rest of the day (11 hours) and noticed it was still trickle charging. Unplugged it and went to bed. Tom stated his continuted to trickle charge for 3 days, so it's safe to say that there's no safety timer. 

Tom, I don't think you had a missed termination... I think you were just using one of those Energizers that loses about a billion mAH overnight due to high self-discharge! :lolsign: 
Of couse I'm kidding. 

Out of curiosity, when you charged the full cell, did you place the cell in the charger and then plug in the charger... or did you already have the charger plugged in and then put the cell in?


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## SilverFox (Dec 30, 2007)

Hello FlashCrazy,

First of all, I don't have any of those "crap" Energizer 2500 mAh cells left... :nana:

I am charging Eneloop cells.

I had 3 cells trickle charging with the light off and simply put the 4th cell back in. The light went on, the cell warmed up, and about 4 hours later it shut off.

Tom


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## Bones (Dec 30, 2007)

SilverFox said:


> I would classify this as a missed termination.



Most interesting Silverfox...

Would you care to speculate on what caused the charge to end after 4 hours?

This is also the first report I've noted of a missed (or delayed) termination, even on a cell that was already fully charged when inserted in the MQN05.

I haven't been able to get a fully charged cell to charge longer than 3/4 of an hour thus far, so I will have to try to duplicate your results by duplicating the same conditions.

I am also curious as to how the improved MH-C9000 would do with the same set of cells under the same circumstances, particularly with regards to temperature.

It would be even more interesting to see how it would do with the same set of cells with three different charge rates, being 300mAh, .5C and 1C.


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## SilverFox (Dec 30, 2007)

Hello Bones,

The battery manufacturers recommend charging NiMh cells in the 0.5 - 1.0C range. I speculate that the charge termination was missed because the low charge rate of 0.15C does not produce a very strong end of charge signal.

I just put the same cells in the C-9000 at a charging rate of 300 mA. The cells had been off the Eneloop charger for about 4 hours. The C-9000 terminated the charge in around 30 seconds.

Tom


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## SilverFox (Dec 30, 2007)

Update:

I pulled the Eneloop charger from power, let the cells rest for a couple of hours, then plugged it back in. All 4 cells terminated in 48 minutes this time. This still seems like a long time, but is a lot better than 4 hours.

Tom


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## FlashCrazy (Dec 31, 2007)

SilverFox said:


> Update:
> 
> I pulled the Eneloop charger from power, let the cells rest for a couple of hours, then plugged it back in. All 4 cells terminated in 48 minutes this time. This still seems like a long time, but is a lot better than 4 hours.
> 
> Tom


 
I was wondering if it would make a difference. I thought I read in the instruction sheet to make sure that you place the batteries in the charger _then _plug it in. I'm pretty sure it was this charger, but I'm out of town now so I don't have the sheet.


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## Bones (Dec 31, 2007)

SilverFox said:


> I pulled the Eneloop charger from power, let the cells rest for a couple of hours, then plugged it back in. All 4 cells terminated in 48 minutes this time. This still seems like a long time, but is a lot better than 4 hours.



But still pretty inconsequential, especially having regard to the following:



SilverFox said:


> In a cell under charge, it seems that the chemical process remains in equilibrium until the charge rate approaches and exceeds 0.3C. Once you get to 0.3C and above, you need charge termination and need to heed all of the warnings about overcharging. However, below that rate, things seem to pretty much say in equilibrium.



I would also note the charge rate of the MQN05 is 150mAh under the 0.3C maximum set out above.

I would note as well that its charge rate is only 100mAh over the 0.1C set out below:



SilverFox said:


> GP states that in mission critical applications such as emergency lighting, you can expect good performance even after 8760 hours of charging at 0.1C.


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## Sub_Umbra (Dec 31, 2007)

Thanks -- this place amazes me.


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## h2xblive (Dec 31, 2007)

I have this charger and have noticed that mutiple charges are probably overcharging the cells.

I recently used one charger to charge 9 cells. My original strategy was to charge 4 cells, then 4 more cells, then the last cell, and do this several times. After I charged the first 4-4-1 (which would take 2-3 days, as I only charged the batteries overnight and in the late afternoon), I'd repeat, but I noticed that the batteries were being charged for like 3-6 hours during the second cycle. When I finally got to the third 4-4-1 charging cycle, the batteries were still "charging" for 3+ hours, ie the green light would be on when the charger is plugged into the wall.

I think there could be several reasons for this:
1. This charger is very conservative as to deciding when the battery really "peaks." This would make some sense, to reduce overcharging and allow the cells to last longer and reduce the risk of a fire or whatever.
2. When I'm charging 4 cells, 3 cells are just fine and aren't charging anymore, but there's some stubborn cell that either keeps it's charge like an Energizer 2500 (ie, can't stay charged) or the cells are otherwise, unbalanced in some odd way.


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## bhds (Dec 31, 2007)

FlashCrazy said:


> I was wondering if it would make a difference. I thought I read in the instruction sheet to make sure that you place the batteries in the charger _then _plug it in. I'm pretty sure it was this charger, but I'm out of town now so I don't have the sheet.



Instructions have you place the batteries in the charger and then plug it in. Doesn't emphasize the fact though.

It does state:

_"Do not plug in upside down. If plugged in upside down , it will finish charging before it is charged."

_Whats that about?


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## SilverFox (Dec 31, 2007)

Hello Bones,

I am confused by your numbers, but first let me offer a disclaimer...  

Hours and hours of testing normal NiMh cells seems to indicate that the transition between doing damage to the cell occurs in the 0.3C range. The low self discharge cells are new and have not been subjected to hours and hours of testing. While they appear to charge just like a normal NiMh cell, this is a gray area.

The charger that I am using charges at 300 mA. With a 2000 mAh Eneloop cell that works out to 0.15C. I would hope that over charging at this low rate would not be a problem with the Eneloop cells, but I did note that the temperature was up a little from normal 0.1C charging. Not enough for me to worry about, but we really don't know.

The GP claim is for normal NiMh cells. I am not aware of any long term studies that have been done with their version of the low self discharge cell.

Tom


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## SilverFox (Jan 1, 2008)

Hello Bhds,

I was also wondering what would happen if you charged with the unit plugged in upside down.

In my case, it seems to do a better job of charging.

Same Eneloop cells with the charger plugged in upside down gave me

1987
1999
1984
1992

Keep in mind that Your Mileage May Vary...

Tom


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## bhds (Jan 1, 2008)

SilverFox said:


> Hello Bhds,
> 
> ....In my case, it seems to do a better job of charging.



:huh:


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## Lite_me (Jan 2, 2008)

Usually, crossing my fingers helps for me. :devil:


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## SilverFox (Jan 3, 2008)

Update:

I charged the same Eneloop cells once again on the C-9000, just to see if the cells were improving with cycling, or if the Eneloop charger actually did a fuller charge charging upside down.

Charging at 1000 mA, top off charge for 2 hours, rest for 30 minutes, discharge at 500 mA.

1914
1937
1906
1933

Interesting results...

Tom


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## Mr Happy (Jan 4, 2008)

SilverFox said:


> Interesting results...


Some testing with my C-9000 suggests it prefers kindness to cells over fullness of charge. Firstly it seems to terminate the charge as soon as the cell voltage reaches 1.47 V, even if a -dV signal has not been seen yet. Secondly, it does not seem to run an intermediate level top-off charge. I left some cells in the charger for over three hours after "Done" appeared, and on discharge they gave no higher readings than if removed immediately on Done.


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## SilverFox (Jan 4, 2008)

Hello Mr Happy,

Yes, this 1.47 figure seems to come up a lot...

The C-9000 is supposed to use a 200 mA top off charge for 2 hours after Done shows up. The way to test for this is to run a normal charge, then remove the cells from the charger and let them sit for 3 hours. Then put them back in the charger and discharge them noting your capacity. Next, do the same thing, but leave the cells in for 2 hours after Done shows, then remove the cells and let them sit for another hour. Do the discharge and compare your discharge values with your previous test.

Tom


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## SilverFox (Jan 4, 2008)

Update:

Same cells, but this time I charged them on the C-9000 at 300 mA. Same top off and rest.

1908
1943
1941
1920

The charging time on the C-9000 at 300 mA is just over 7.2 hours.

Tom


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## Mr Happy (Jan 7, 2008)

SilverFox said:


> Hello Mr Happy,
> 
> Yes, this 1.47 figure seems to come up a lot...
> 
> ...


I do not have results for this exact test, but I do have results comparing a timed full charge with an automatically terminated charge. Using some Eneloops which have previously tested well, I attempted first to find their maximum capacity at 100% of charge.

For the first part of the test I discharged the cells on the C-9000 and then gave them a timed constant current charge of 300 mA over a period of about 8 hours to a total of 2400 mAh (nominally 120% of capacity). At the end of the charge the cell voltage was reading 1.51 V and the cells were barely above room temperature. The cells were removed from the charger and rested for 4 hours. I then measured the charge by discharging at 500 mA, giving the following result for the four cells:

1917 1890 1866 1903

These results I believe to indicate close to 100% capacity for the cells in question.

For the second part of the test I put the cells on a standard 1 A charge on the C-9000, leaving them on the charger for about 2.5 hours after Done showed. As expected, Done showed as soon as the cell voltage reached 1.47 V. About 1.5 hours after Done, the voltage had increased to 1.48 V and at 2.5 hours it had decreased to 1.47 V again. I removed the cells and rested them for 4 hours, and then discharged them at 500 mA getting the following readings:

1872 1848 1826 1859

This charge was not quite as complete as the first, being about 97.5% of the "maximum" charge, but in practical terms I doubt the difference would be noticed.

Edit: further test results added:

Test 3 was a standard 1 A charge on the C-9000 as above, but removing the cells as soon as Done showed and then resting them for 4 hours before discharge. The measured readings on discharge were:

1782 1760 1739 1766

This charge was substantially less than the previous test, so for the fullest charge it does appear beneficial to leave cells on the C-9000 for two hours or so after Done appears.

The final test was to charge the cells overnight on the Duracell Power Gauge charger (model CEF21). Then discharged at 500 mA on the C-9000 as before. The measured discharge readings were:

1911 1881 1862 1897

These last readings are very close to the maximum capacity as measured by the timed charge test.


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## SilverFox (Jan 8, 2008)

Hello Mr Happy,

Now we are getting into a bit of a gray area.

The question often comes up "What is a full charge?" With normal NiMh cells, the excess charge will quickly bleed off and you won't see much difference between charging at 300 mA or charging at 1000 mA. The low self discharge cells are different. 

Since it is "difficult" to generate a end of charge termination signal at 300 mA, I could make an argument that when you are charging at 300 mA, you are overcharging the cells. Your true capacity is what you are getting when you charge at 1 amp, because charging at 1 amp generates a strong end of charge signal.

However, the "argument" pales when you consider the results from the 0.1C 16 hour Break-In cycle.

At any rate, it's something to consider.

Tom


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## Mr Happy (Jan 8, 2008)

My feeling is that people would like their cells to hold the maximum charge they are capable of, presuming they can be charged to that state without damage.

With NiMH chemistry, it is my understanding that when a cell is reaching a full state of charge the shuttle reactions start to predominate and bypass the extra current through the cell without accumulating further charge. As long as the cell does not get hot, moderate periods of this overcharge process cause no harm.

This was my intent with the timed 300 mA charge. By feeding in 120% of the nominal capacity the cells were pushed right into the shuttle zone and some of the charge current was wasted. However, it did ensure that as much charge as possible was stored in the cell. I observed the cells to remain at room temperature right to the end, so I am working on the assumption they were not harmed by this.

Your question about how quickly that "last drop of charge" bleeds off on storage is interesting, and potentially leads to another experiment to find out. My true purpose however was just to establish a baseline against which I could assess the completeness of charge for alternative charging methodologies and chargers. I am still completing those tests and will post the results when I have them.

In normal usage, I am sure that any charge above 95% of true maximum capacity is a full charge for practical purposes.


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## Mr Happy (Jan 8, 2008)

I have updated post #34 with further test results.

Here is a summary of the results, showing discharge capacity and charge completeness on the set of 4 Eneloops under test with different charge strategies and chargers. The figures are the measured mAh on discharge at 500 mA using the Maha C-9000. The percentage is the relative charge compared to the 100% baseline capacity. After each charge the cells were rested for 4 hours before discharge.

Test #1: Timed charge at constant current of 300 mA for 8 hours to 2400 mAh supplied:

1917 1890 1866 1903 -- 100.0%

Test #2: Charged on C-9000 at 1000 mA, cells left on charger for 2.5 hours after Done showed:

1872 1848 1826 1859 -- 97.7%

Test #3: Charged on C-9000 at 1000 mA, cells removed from charger immediately after Done showed:

1782 1760 1739 1766 -- 93.0%

Test #4: Charged on Duracell Power Gauge charger model CEF21:

1911 1881 1862 1897 -- 99.7%

Conclusions?

To get a full charge on Eneloops with the C-9000 the cells should be left on the charger for 2 hours after Done appears so they get a top-off charge.

The Duracell Power Gauge does well at putting a full charge into cells. However, since it takes 5-6 hours to charge Eneloops it is not faster than the C-9000 plus two hour top-off.

(Comment: As noted earlier, the C-9000 appears to have a safety termination when the cell voltage reaches 1.47 V, which cuts in and stops charging Eneloops before the -dV signal is seen. This is apparently why the top-off charging period is so important for this type of cell.)


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## matrixshaman (Jan 8, 2008)

SilverFox said:


> Hello Bhds,
> 
> I was also wondering what would happen if you charged with the unit plugged in upside down.
> 
> ...



Uhh - yes gravity helps drain the last of those electrons out of the charger :thinking:
That's a very interesting observation but of course my explanation is just a joke... so what could possibly cause this? I'm very interested if this can be duplicated. I assume by upside down you mean the charger has a non-polarized plug that will go in polarized outlets either way? If this can be repeated with consistent results then you may really be onto something very interesting. Since one side of the outlet is at Earth ground it brings up some fascinating thoughts.


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## dulridge (Jan 8, 2008)

matrixshaman said:


> Uhh - yes gravity helps drain the last of those electrons out of the charger :thinking:
> That's a very interesting observation but of course my explanation is just a joke... so what could possibly cause this? I'm very interested if this can be duplicated. I assume by upside down you mean the charger has a non-polarized plug that will go in polarized outlets either way? If this can be repeated with consistent results then you may really be onto something very interesting. Since one side of the outlet is at Earth ground it brings up some fascinating thoughts.



Just a guess, but I'm assuming that they mean with the cells on the underside of the charger. I'd guess it could very likely undercharge in this position if the cells fell out...


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## Mr Happy (Jan 8, 2008)

dulridge said:


> Just a guess, but I'm assuming that they mean with the cells on the underside of the charger. I'd guess it could very likely undercharge in this position if the cells fell out...


I'd assumed it was something to do with temperature and air circulation. In some orientations the heat could be less able to escape, which might lead to overheating problems, or could affect the operation of the temperature sensor.


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## dulridge (Jan 8, 2008)

Mr Happy said:


> I'd assumed it was something to do with temperature and air circulation. In some orientations the heat could be less able to escape, which might lead to overheating problems, or could affect the operation of the temperature sensor.



Which makes a lot more sense then my facetious reply. I too would reckon heat has something to do with it.


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## h2xblive (Jan 9, 2008)

So maybe removing that slide cover during charging might lead to overcharging?


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## radellaf (Jan 9, 2008)

I have always wondered about that cover, as usually you want full air circulation when charging. Unless, perhaps, temperature is a primary termination method.

But then, the 2-position charger with the slightly higher rate does not have a cover. It also has a warning against "upside down" charging. It also does not say if that means batteries on the bottom or positive terminals pointing down.

The 2 position at least does have a temperature sensor below the batteries on the circuit board. I don't know how they use that. (emergency limit, abs temp, temp rise, dT/dt).

I have been cautious about my 250mAh AAA cell in these, though. The rate is very high (300, 350?). I must imagine it would sense the voltage peak, but I don't know what the top off current would be or for how long.


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## Bones (Jan 10, 2008)

radellaf said:


> I have been cautious about my 250mAh AAA cell in these, though. The rate is very high (300, 350?).


According to the MQN05 specifications, the rate for AAA cells is really a more gentle 150mAh:









radellaf said:


> It also does not say if that means batteries on the bottom or positive terminals pointing down.



Based on it's context, the "upside down" warning for the MQN05 appears to be referring to the charger itself, and it actually states "Do not plug-in upside down" in the charging instruction:









radellaf said:


> ... but I don't know what the top off current would be or for how long.



According to this post by FlashCrazy, the MQN05 applies more of a "maintenance charge", which SilverFox indicated in a later post is probably continuous:



FlashCrazy said:


> When the charger light extinguished, the charger pulsed the battery with anywhere from 10 to 40 mA for about a 1/4 second, then rested for 8 seconds, then repeated. It continued this cycle for one minute, then rested for a full minute. It then pulsed again as before for another minute, then rested a minute. This cycle repeated for as long as I had the battery in place. I took it out after about 20 minutes. I'm not sure one would call this a trickle charge, maybe more of a "maintenance" charge. Pretty cool, nonetheless.


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## SilverFox (Jan 10, 2008)

Hello Bones,

:devil: I may have figured it out... :devil:

If your socket happens to be a little loose or worn, plugging the unit in upside down could cause it to fall out of the socket part way through the charge cycle.

This would result in under charged batteries...  

Tom


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## Bones (Jan 10, 2008)

SilverFox said:


> Hello Bones,
> 
> :devil: I may have figured it out... :devil:
> 
> ...



Yours would seem to be the explanation most in line with Occam's Razor SilverFox, but I am leaning more and more towards it being a baseless statement tossed in by a slightly maniacal Sanyo engineer who is now gleefully monitoring this forum.


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## Mr Happy (Jan 10, 2008)

If they really cared, wouldn't they have fitted it with a polarized plug so you can only plug it in one way round?


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## hank (Jan 10, 2008)

Clarify 'upside down' -- you mean physically putting the charger upside down, so the battery slots are underneath? So presumably the whole charger might overheat a bit more?


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## Bones (Jan 10, 2008)

hank said:


> Clarify 'upside down' -- you mean physically putting the charger upside down, so the battery slots are underneath? So presumably the whole charger might overheat a bit more?



That's correct hank, except the batteries sit inside the 'x' depicted in the images set out below, so the charger should actually heat up less when it's upside down. The heat has less distance to radiate before exiting the charger.


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## hank (Jan 10, 2008)

Uh, oh, did you say it's NOT a polarized plug? 

Both prongs the same size? Not the usual wider prong for neutral?

Our electrician, puts the ground pin UP, so if a grounded plug works loose and something conductive falls down between plug and socket, it bounces off the ground pin or shorts to that, lessening the odds of shorting between hot and neutral.

Which I've seen happen. PopBANG!

Which would mean, if they're talking about a question of polarity rather than physical/heat rising, their advice would be backwards for us, because our plugs are upside down.

My head hurts.

No, wait, maybe _I'm_ upside down, in which case ...


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## Bullzeyebill (Jan 11, 2008)

Yes, both prongs are the same size.

Question. The charger rate for AA is 300mA's X4, as stated on back of charger. If you charge only two cells will the charging rate be 600mA's X2? One at 1200ma's? Anyone checked this?


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## Turak (Jan 11, 2008)

I have verified that the MNQ5 uses 4 independent channels that supply 300mA per channel. No matter how many batteries (i.e. 1, 2, 3, or 4) you are charging. Put 1 battery in and it gets 300 mA, put 4 batteries in and each gets 300mA for a overall total of 1200mA if you added up each channel. It also appears to be using -dV or 0dV for its termination method.

As to the whole right-side up vs. upside down discussion..... because one side is hot and one side is neutral, depending on the actual circuit design, it REALLY can make a difference. I have not reverse engineered and drawn the circuit out to really see if it does or not...but it is possible that it could. Although if it really does make a difference, as stated by others, I can not understand why they would not have used a polarized plug.

I have used the charger quite a bit.....it seems to perform quite well, although it may be a little slow for some peoples taste. The only real complaint I would have is the way the AAA batteries fit in it on an angle. At first I thought something was wrong with the charger, but nope...kind of a strange design. As for the cover...take it off and pitch it in a drawer....useless.


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## SilverFox (Jan 11, 2008)

Hello Turak,

Did you happen to notice the value that they are using for the -dV?

The cover is designed to keep the cells in place while traveling with them. The charger is designed so that it does not drain the cells if they are left in after removing it from power. With the cover on, you can throw the charger and cells in your bag and not have to worry about the cells falling out.

Tom


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## radellaf (Jan 11, 2008)

Which blade is hot or neutral could only make a difference if the circuit had another connection outside itself for reference.


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## Bones (Jan 11, 2008)

I've been rotating a single Eneloop through each of the slots, and to date the charger has charged it fully and terminated about when expected.

One pleasant surprise is that after approximately 6 1/2 hours in the charger, the cell has only been slightly above room temperature when the charges terminate.

This makes me think that the cells are absorbing most of their heat from the charger itself when all four slots are being utilized.


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## SilverFox (Jan 12, 2008)

Hello Bones,

I have been playing too...  

I confirmed that one cell charges in the same amount of time as 4 cells, so it seems that the 300 mA charge rate for each slot is correct. 

I then put one cell in to charge, and an hour later put a second cell in to charge. The charge light went out about an hour later than it did for charging one cell.

Tom


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## Bones (Jan 12, 2008)

SilverFox said:


> I then put one cell in to charge, and an hour later put a second cell in to charge. The charge light went out about an hour later than it did for charging one cell.



Good stuff SilverFox.

This is one (of many I'm sure) that never occurred to me.


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## VidPro (Jan 12, 2008)

FlashCrazy said:


> \
> Well, today I tested it using an ammeter. I put one AAA Eneloop in the charger. During charge, the charger pulsed the battery with 610 mA for about a 1/4 second, then rested for 3/4 seconds, then pulsed again, rested, etc. Averaged out, this correlates with the 150 mA charge rated listed on the back of the charger for AAA's.
> 
> When the charger light extinguished, the charger pulsed the battery with anywhere from 10 to 40 mA for about a 1/4 second, then rested for 8 seconds, then repeated. It continued this cycle for one minute, then rested for a full minute. It then pulsed again as before for another minute, then rested a minute.


 
so with an AAA it uses a 600ma (type) charged pulsed 25%on 75%off. (averaged ~150)

can we assume that with a AA it uses a 600ma for 50%-50% (averaged ~300)

the minute rest on the "maintance" charge is interestingly weird. 
i just need more pieces of data, because the AAA is different rate.
what would the "maintance" charge be for AA ?

with an LSD a maintance charge , could be more "topping"  because its not constantally loosing as much.

What is the OPEN voltage? if its readable at all, might take a real trick to get it.

----------------------

i think one more great piece of data would be usefull. i will see if i can set it up.
Use a power supply (not pulsed or averaged) and continually pummel the ENLOOP (specifically) with various overcharge rates like 200-300-400, till it gives in and V-drops. try and find its breaking point.
then use a powersupply with 50-50 pulse 1 sec, and pummel it till it v-drops (something harder to read without computer) and find its breaking point then .

also it would be interesting to see the termination of the enloop charger, occur on a voltage scope, that is always great info too.

thanks everyone for the data.

i actually LIKE a lot the 9000s way of terminating at high voltage, then finishing by toppin, if it would finish completly, that would be great. so some people would be frustrated by the lack of total capacity it charged to, and time to topping, but that is IMO a cool method. might make paying for one more worth it.


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## Turbo DV8 (Jan 13, 2008)

Mr Happy said:


> If they really cared, wouldn't they have fitted it with a polarized plug so you can only plug it in one way round?


 
But then you would need a reverse-polarizing adapter for charging south of the equator, since there the charger would again be upside down.


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## Mr Happy (Jan 13, 2008)

Turbo DV8 said:


> But then you would need a reverse-polarizing adapter for charging south of the equator, since there the charger would again be upside down.


Yes, but south of the equator gravity acts upwards instead of downwards, so it all cancels out in the end.


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## Albinoni (Jan 13, 2008)

Some questons I would like to ask regarding this charger.

1. Will this charger charge all 4 batts at the same time or does it do one at
a time.

2. Will it discharge batteries ?

3. What's a trickle charge, is it basically just a slow charge ?


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## SilverFox (Jan 13, 2008)

Hello Albinoni,

1. Yes, it charges all the batteries put in it at the same time. You can charge from 1 to 4 batteries in it.

2. No.

3. A trickle charge is a very low rate charge that is designed to overcome the self discharge rate of the battery. Since the Eneloop cells have a very low self discharge rate, I believe that no trickle charge should be needed. It is better if the charger simply shuts off at the end of the charge.

Extended trickle charging damages batteries. It causes the electrolyte to dry out and can cause crystal formation within the cell the contributes to voltage depression, more incorrectly known as the memory effect. With proper design you can constantly trickle charge and still have the device work (for example emergency lighting), but it is hard on NiMh batteries.

Tom


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## Marduke (Jan 13, 2008)

Albinoni said:


> Some questons I would like to ask regarding this charger.
> 
> 1. Will this charger charge all 4 batts at the same time or does it do one at
> a time.
> ...



Based off your other question 


> I bought a Sanyo Eneloop charger to use with my Eneloop batts. This charger will charge both AA and AAA batts and also came with 4xAA batts included as well.
> 
> Ok I know this is not a Maha 9000 but as a general charger for the Eneloop is it good and also do the batts get very hot after they charge, also after a charge will it automatically switch off. Also mine has got two green LED's on it.
> 
> ...



You have the 6U, not 5U charger, which is 2-channel, not 4-channel

There are several threads on both charges here, so please read those threads for your questions.


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## SilverFox (Mar 4, 2008)

Update:

I have been testing some "well used" Eneloop cells with this charger. As NiMh cells age, their internal resistance increases. This increase in internal resistance causes the cells to heat up more during charging, and forces the voltage up during the charge. 

Several test runs using these aged cells seem to indicate that this charger terminates on maximum voltage. I see the voltage rise to around 1.55 volts, then the charge terminates.

To verify this, I took the same cells and charged them on the BC-900, which also seems to terminate at around 1.55 volts. I used a charge rate of 200 mA, and noted that the discharge capacities were very similar between the BC-900 and the NC-MQND5U. 

The C9000, as initially pointed out by NiOOH, seems to terminate at a maximum voltage of 1.47 volts. The same cells charged at 200 mA on the C9000 and left on the charger for the top off charge, came in with a little less capacity than these other chargers. Still in the same ball park, but a few percent lower. 

The initial question that I had with this charger was "How do they reliably terminate the charge at the slow charge rates used?"

The answer is two fold. First they terminate on a maximum voltage. Second they have a back up timer termination.

I believe this approach favors aged cells, but can be hard on new cells. A new cell will end up at a lower maximum voltage than a used cell, so when charging new cells, the charger will continue on until it times out. Fortunately, or unfortunately depending on your perspective, a few hours of overcharging will quickly "age" the cell.

While this round of testing answers some questions, others arise... Is the cycle life of a battery influenced more by the rate of charging, if kept within reason, or by the termination method? Is peak voltage termination superior to -dV termination, or is it just an inexpensive way to terminate that is adequate?

There are many uncontrollable variables that crop up when testing cells that are near the end of their useful life. I am not sure I can come up with a reasonable way to control those variables. I will have to think on this for awhile...

I do know that a very high percentage of the people who contact me about battery problems are using slow chargers. If other slow chargers use similar termination methods, this may be significant, but let's, for now, just call it an observation.

I have ruined several sets of cells using slow chargers. I have had much better success using chargers that charge in the 0.5 - 1.0C range. Thus, I think fast charging is a better way to go. 

This charger seems adequate for the job. It may not be the best for the batteries, but it seems like a reasonable compromise. 

By the way, comparing the discharge capacities of these aged cells after charging them on the Eneloop charger, the BC-900 at 1000 mA, and the C9000 at 1000 mA, I find that the discharge capacities are virtually the same. 

Tom


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## Handlobraesing (Jun 8, 2008)

I have partially reverse engineered this sucker.

The AC power is stepped down to 2.2v DC by a switch-mode power supply. The battery side and AC side is galvanically isolated and power transfer is magnetic and feedback is through an optocopupler, just like most other SMPSs.

It employs a single current source sequential charging topology.
The current source is 0.6A for AA and 1.2A for AAA and each operates at 25% duty cycle and each slot receives a time weighed average of 0.15A or 0.3A.

It takes two seconds to progress through all 4 cells, so the frequency is 0.5 Hz and each cell receive 0.5s on/1.5s rest.


There are two benefits with this design. The electrochemical efficiency of battery is higher at 1.2A than 0.3A. Given a 2,000mAh cell, you need to charge at true 300mA(0.15*It) for 16 hours to fully charge, however when you charge at 1.2A(0.6*It ) the charge efficiency during the 25% charging duration is more efficient, so even though the time weighed average current is the same, you will actually achieve a full charger sooner.

In other words, the energy pushed into the battery during the two second period is the same, but the total energy stored by the battery at 1.2A for 0.5second is more than that of 0.3A x 2 seconds.

Another benefit is that you only need one constant current circuit. 
quadrant 1 =cell 1, quadrant 2 is cell2, etc. The constant current source provides current the entire time when all quadrants are loaded, but when there is no cell in one of the bays, it simply pauses for half a second and move onto the next one. 

This is topology is quite common with Sanyo chargers and with some of their chargers, you can actually charge 2 cells at faster rate. This is made possible by allocating two quadrants to each cell. 

The current is selected by changing the shunt, which provides a feedback to the constant current source.
x..........A.......B
|-^^^-|-^^^|

The B terminal is connected to AAA (-) terminal bar and A terminal to AA(-) terminal. The two resistors are identical and the shunt generates twice as much voltage per amp with AAAs causing the current source to halve the current output. When you're charging AAAs, you can actually connect a scope/DMM between the AA and AAA negative terminals to observe the charging current. 

With an AAA inserted, ground instrument to B(AAA negative), channel 1 to A and if you desire to monitor cell voltage, connect the second channel to B

*Thermal*

Possible explanation for the claimed "premature termination" with inverted is the heat from the charging circuitry rising by convection and setting off the thermal termination prematurely. 

An interesting experiment would be to place a fully charged cell in slot 1 and empty cell in slot 2, leave slot 3 empty then an empty cell in slot 4. 

Compare the discharge capacity of the empty cell charged in slot 2 and the one from slot 4. If the cell from slot 2 has much less charge, it would indicate that the heating of charging a already charged cell in slot 1 adversely caused the slot 2 to shut down. 

Neutral/hot of the AC line is non-issue. The charging control is completely isolated by an isolation transformer and an optical coupler. 

Board side (click photo to expand) 
*warning* 1480 x 2560 
I had to change to greyscale to be able to maintain a good resolution and be within the 1MB limit of Photobucket upload.






Component side (click photo to expand) 
The orange glass body diode like things are thermistors and blue resistors are ~0.1ohm shunts. 
There are two thermistors, each serving two bays. They fit into the slits placed between two cells in the housing shell. 




user view






internal view
note the two channels between 1&2 and 3&4 for thermistors


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## Mr Happy (Jun 8, 2008)

That's fascinating.



> The electrochemical efficiency of battery is higher at 1.2A than 0.3A. ... In other words, ... the total energy stored by the battery at 1.2A for 0.5second is more than that of 0.3A x 2 seconds.


Do you have a reference for this? It seems contrary to expectation, actually. The charging reactions involve various rate limiting steps, specifically the diffusion of various chemical species to and from the electrode surfaces and through membranes. A lower charging rate would seem to allow more current to take part in the thermodynamically reversible charging reactions and less current in irreversible heat generating paths.

What about the influence of charging with the lid closed and the lid open? The instructions say to charge with the lid closed. It would be interesting to discover whether the thermal sensors take part in the normal charge termination decision, or whether they are just an over temperature safety feature.

Did you have any ideas about repeating what those Japanese guys did and figuring out how to install four individual charging status indicators? I believe they found the location on the circuit board of a logic level that indicated whether each channel was charging or not and hooked in a driver transistor and LED to that point. Of course it would be a bit awkward with the sliding lid. I think they used a slightly different model of charger.


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## Handlobraesing (Jun 8, 2008)

Mr Happy said:


> That's fascinating.
> 
> Do you have a reference for this? It seems contrary to expectation, actually. The charging reactions involve various rate limiting steps, specifically the diffusion of various chemical species to and from the electrode surfaces and through membranes. A lower charging rate would seem to allow more current to take part in the thermodynamically reversible charging reactions and less current in irreversible heat generating paths.


16 hours is the common prescribed full charge duration at 0.1 It The Sanyo engineering handbook talks about you only lose capacity to self discharge at a rate of about 1/500 It (for regular NiMHs) and you won't be able to actually charge at a charging rate this low, but you can alleviate that by using higher charge current to yield a time weighed average of 1/500 It. 

I will run an experiment and let you know, but I don't have the perfect chargers I've a 330mA constant current charger, 300mA pulsed charger.

I can run both chargers for exactly an hour... then report back the captured charge (through discharging the cells)

You'll need a 300mA (1.2A x 25%) source and a 300mA (300mA x 100%) source and they both need to be calibrated..



> What about the influence of charging with the lid closed and the lid open? The instructions say to charge with the lid closed. It would be interesting to discover whether the thermal sensors take part in the normal charge termination decision, or whether they are just an over temperature safety feature.


The Sanyo engineering handbook also says below about 0.5 It, -dV is not very obvious and termination is uncertain. I think that the cover serves as a jacket to assist in temperature based detection. I'm currently running a charge cycle with two empty eneloops.

first one in slot 1, fully charged cell in slot 2, slot 3 empty and the second one in slot 4 to interfere with the temperature sensing method. If temperature is the primary means of charge termination, the cell in slot 1 won't charge fully because of the fully charged cell in slot 2 heating. 



> Did you have any ideas about repeating what those Japanese guys did and figuring out how to install four individual charging status indicators? I believe they found the location on the circuit board of a logic level that indicated whether each channel was charging or not and hooked in a driver transistor and LED to that point. Of course it would be a bit awkward with the sliding lid. I think they used a slightly different model of charger.



No... link?


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## Mr Happy (Jun 8, 2008)

Handlobraesing said:


> No... link?


I'm sorry, I've lost the link. I remember it was referenced from somewhere in this forum. If I find it again I'll post it.


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## hank (Jun 9, 2008)

> I think that the cover serves as a jacket to assist in temperature based detection. 

Whoah, I wonder if this applies to all the chargers that have covers.
I got a RayOVac PS3 a while back (in a rush) with a cover, always used it with the cover open, and just now had it fail to stop charging an AAA Eneloop (one of a pair, the other one terminated properly).

Maybe I should start using it with the cover closed? No instructions I've ever seen mention this notion. Maha's little chargers also have covers. Hmmm.

I'm not smart enough for this stuff.


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## Unforgiven (Jun 9, 2008)

hank said:


> > I think that the cover serves as a jacket to assist in temperature based detection.
> 
> Whoah, I wonder if this applies to all the chargers that have covers.
> I got a RayOVac PS3 a while back (in a rush) with a cover, always used it with the cover open, and just now had it fail to stop charging an AAA Eneloop (one of a pair, the other one terminated properly).
> ...




It depends on the charger and the manufacture. The MAHA MH-C401FS (PDF download from MAHA) says to leave the cover open. It would be best to consult the manual for each charger to make sure.


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## Black Rose (Jun 9, 2008)

hank said:


> Whoah, I wonder if this applies to all the chargers that have covers.
> I got a RayOVac PS3 a while back (in a rush) with a cover, always used it with the cover open, and just now had it fail to stop charging an AAA Eneloop (one of a pair, the other one terminated properly).
> 
> Maybe I should start using it with the cover closed? No instructions I've ever seen mention this notion.


I have a Rayovac PS16 that has a clear blue cover. I've always used it with the cover closed.


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## Handlobraesing (Jun 9, 2008)

*Continuous current vs pulsed charging efficiency*

Purpose: testing the difference in charge efficiency between constant current vs using pulse charging to yield a similar time weighed average.

Chargers:
1:
380mAh constant current series charging. Linearity was tested and it was able to provide a constant 380mAh regardless of state of charge. The spec is 360mAh, however the measured current is 380mAh throughout the whole charging process

2:
442mAh pulsed charge. Measured at 1.768A * 25% duty cycle @ 0.5Hz. Spec is "450mA" 

Each charger was filled with two fully drained 2650mAh NiMH set and allowed to charge for 2 to 3 hours. Exact duration is not know, because I used a cheap appliance timer. What I do know is that two chargers were put in the same power strip, therefore the two turned on and off at exactly the same time, which is what matters here.

After the charging process was completed both cells were drained on the MH-C9000 at 1A:

Set 1 yielded 913mAh and 922 mAh, avg 917mAh 
Set 2 yielded 1122 and 1128 mAh, avg 1125mAh

Possible source of error: the charging curent was not low enough to contrast the difference and ideally I would have used 260mA CC and 1.04A * 25% @ 0.5Hz duty cycle, so that they'd actually have the same average current. 

The result form this experiment indicates that while the charging current was only increased by 16.3%, the charged capacity was increased by 22.7%. The capacity between two cells used in each charger was minimal, so I don't suspect it was a glitch.


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## Lite_me (Jun 10, 2008)

Unforgiven said:


> It depends on the charger and the manufacture. The MAHA MH-C401FS (PDF download from MAHA) says to leave the cover open. It would be best to consult the manual for each charger to make sure.


The latest release of the C401FS have been "improved". They have don't have a cover anymore.


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## Unforgiven (Jun 10, 2008)

Lite_me said:


> The latest release of the C401FS have been "improved". They have don't have a cover anymore.




Thanks for the information. I will have to find out what the improvements are. I really like my C9000 but would like a more compact "good" charger to take with me when I am on the road.


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## Lite_me (Jun 10, 2008)

Unforgiven said:


> Thanks for the information. I will have to find out what the improvements are. I really like my C9000 but would like a more compact "good" charger to take with me when I am on the road.


Actually, the only improvement I'm aware of, is that they've removed the cover. I was attempting humor.  

I like mine. All it does is work. It may seem expensive, but is it really? It has served me well. 

Here's the "improvement" I spoke of...


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## Wattnot (Aug 1, 2008)

I finally found one of those Walmart clearance deals and now have an MQN05U charger. I have a couple of questions:

1. Has anyone tried mixing cells? Like capacities, brands but namely, AA and AAA being charged simultaniously? The instructions (and a search here) didn't yeild any info on this. It seems to me the independant channels make this okay but I thought I would ask to be sure.

2. I now have THREE NIMH chargers. I almost have more chargers than NIMH batteries! I was thinking of selling my older MH-C204F because it's only a two channel but then again it's faster than the Eneloop one. Opinions on the C204F? They have newer models out now . . . I bought this one before I knew a lot about batteries!

Thanks!


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## Bones (Aug 2, 2008)

Wattnot said:


> ...
> 1. Has anyone tried mixing cells? Like capacities, brands but namely, AA and AAA being charged simultaniously?
> ...



As long as they are NiMH cells, you can mix and match brands and capacities to your heart's content in the MQN05 Wattnot.

One caution I would put forth though, is not to insert cells into the charger while it's powered up.

While it may have been coincidental, the only report I've seen of a delayed termination with the MQN05 involved just that.



Wattnot said:


> ...
> 2. I now have THREE NIMH chargers. I almost have more chargers than NIMH batteries! I was thinking of selling my older MH-C204F because it's only a two channel but then again it's faster than the Eneloop one. Opinions on the C204F? They have newer models out now . . . I bought this one before I knew a lot about batteries!
> ...



If you think you might have an occasional need a fast charger, you might consider holding on to your MH-C204F until, hopefully, the MQH03 becomes available in the USA.

However, considering the Eneloops ability to retain its charge, it would probably be easier on them and you to just pick up an extra set; and then get into the habit of charging them well in advance of when they will most likely be needed.


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