Maha MH C808M Charger

[bcwang]

Hello Bcwang,

My charger is very consistent from slot to slot. I tested this with 2 cells, 4 cells, 6 cells, and 8 cells. I know this is not "exhaustive," but it gave me a pretty good indication of its operation.

I have been using some very good Powerex 2500 cells for this testing. They seem to handle hard use (and some abuse ) very well. A few more cycles in my Mag85, and I will add them to the NiMh shoot out thread.

Tom

I'm definitely going to try to figure out if this was a fluke or completely repeatable. I just wish I had a better way to test capacity quickly than the BC900. I do notice the capacity coming out of the 808m after a 30 minute wait before testing in the bc900 is much less than letting the bc900 do a charge and test cycle which has no wait time. I wonder how much that 30 minute wait hurts capacity. I'm talking about the difference between 2250mah against 2550mah which is quite significant.

 

[wptski]

bcwang:

I wonder if that's what I'm seeing also? I charged four cells in the C808M and then D/C the four as a pack on the Triton.

 

[bcwang]

bcwang:

I wonder if that's what I'm seeing also? I charged four cells in the C808M and then D/C the four as a pack on the Triton.

Tried these two tests with the same set of batteries. The 808M after 8 hours on the charger at the normal setting (around 7 hrs is trickle), I got around 2230-2370mah depending on the cell or charge position. Only waited 5 minutes or so between pulling the batts out of charger and placing in bc900 tester.

With the C204W, after 8 hours on the charger ( around 5 hrs is with the light green), I got 2510-2540mah depending on the cell. Waited 1 hour between pulling batts out of charger and putting in tester. I had to drive take it to work to monitor the discharge.

So it seems the 808M doesn't charge as fully. My cell imbalance is more of a concern though, the different slots are not performing the same. I did a test of the voltage after coming off the charger last night. The cells ended at 1.39v on the first two slots, 1.40v on 3-4. The last 4 some were 1.40 and some 1.39v but I didn't pay too much attention on the order, but it was mixed. The C204W comes off at 1.41v

 

[SilverFox]

Hello Ben,

I just pulled 8 cells off of the charger. Most of them were at 1.44 volts. The lowest was 1.43 volts, and the highest was 1.46 volts.

Your cells at 1.39 and 1.40 volts do not seem to be fully charged.

Tom

 

[bcwang]

Hello Ben,

I just pulled 8 cells off of the charger. Most of them were at 1.44 volts. The lowest was 1.43 volts, and the highest was 1.46 volts.

Your cells at 1.39 and 1.40 volts do not seem to be fully charged.

Tom

I should bring my multimeter home to test with, I was actually using the bc900 to test the voltage, it might load the cell a bit dropping it from the resting voltage. If not, it could be from testing the cells after they were out of the charger for 30min-2hrs. My BC900 was in progress at the time so I was waiting for it to free up to measure the voltage coming off my maha chargers. But my cells that measured 1.41v did test out to around 2550mah at 500ma discharge.

 

[tareed69]

I have the c801d version of this charger, it only charges AA/AAA. I have a problem, it has on 3 seperate occasions overcharged my cells. It just happened now, I inserted 2 AAs and clicked the soft mode and condition mode. First it charges before discharges. Problem is, it never quit charging and the batteries got extremely hot. When I pulled them out, the voltage was 1.52 and quite uncomfortable to touch. They were Rayovac 1800 AA NiMH.

Do you think I have a defective charger?

 

[willchueh]

I have the c801d version of this charger, it only charges AA/AAA. I have a problem, it has on 3 seperate occasions overcharged my cells. It just happened now, I inserted 2 AAs and clicked the soft mode and condition mode. First it charges before discharges. Problem is, it never quit charging and the batteries got extremely hot. When I pulled them out, the voltage was 1.52 and quite uncomfortable to touch. They were Rayovac 1800 AA NiMH.

tareed69,

A quick way to check if the charger is working properly:

1) Unplug
2) Plug in power and watch the power up diagnostic... you should see all the symbols go on from right to left (DONE, CHARGE, 3-level battery etc).
3) After that's done, the screen should remain off with NO symbols at all. You might want to wait for about 10 sec to make sure no symbol pops up by itself.

William

 

[willchueh]

I have the c801d version of this charger, it only charges AA/AAA. I have a problem, it has on 3 seperate occasions overcharged my cells. It just happened now, I inserted 2 AAs and clicked the soft mode and condition mode. First it charges before discharges. Problem is, it never quit charging and the batteries got extremely hot. When I pulled them out, the voltage was 1.52 and quite uncomfortable to touch. They were Rayovac 1800 AA NiMH.

tareed69,

Assuming the power up diagnostic is good, here are some possibilities:

1) 1.50V is a reasonable voltage for NiMH if you tested them immediately off the charger. The charger's absolute cutoff (Vmax) is at 1.60V.

2) How long have you had the cells? Are these recently purchased? If so, your "new" cells may not be new at all. I would bet the Rayovacs are at least 18-24 month off the production if you'd just purchased them. Cells like these develop a extremely high impedence due to prolonged storage and would cause high temperature (~130F) when first charged. If the cells are manufactured well, then the impedence should drop after a few cycles.

Hope this info helps!

William

 

[tareed69]

Thanks for the response, the batteries are ancient, that probably is the problem.

 

[TooManyGizmos]

willchueh : Please help ..........

For the first 3 weeks my MaHa C-808-M charger worked just fine ................

But now :

I'm having problems too .
When I insert the first AA battery in the far left slot - and within 2 to 8 seconds press the soft charge button - it won't go into soft charge mode . The word softcharge won't appear on the display . I am pressing and holding the button for 5 seconds - but still nothing .

If I press condition - the word condition will appear - so that function seems o.k.


I have un-plugged *AC* power - and the *DIN* connection cable , waited 5 minutes - then plugged all back in so it would re-set and go thru *self test* - all batt. symbols blinked from right to left . I wait 5 minutes after selftest has finished B-4 inserting battery and pressing softcharge button . I have done this whole proceedure several times , but still can't get it to go into softcharge mode . The word won't appear in the display. The first batt. icon on left will register and start blinking as it normally does and the white display light is working......but no softcharge .

Also have tried several different AA batteries - they are all 2600 MiAh's - 2 months in use - and have been thru at least 6 charges on this charger in 3 weeks and all was fine till now .

Have done ALL I know to do - can you offer any advice , thanx willchueh , for you help.

 

[willchueh]

When I insert the first AA battery in the far left slot - and within 2 to 8 seconds press the soft charge button - it won't go into soft charge mode . The word softcharge won't appear on the display . I am pressing and holding the button for 5 seconds - but still nothing .

TooManyGizmos,

During power-up, the "CONDITION" and "SOFT CHARGING" icons should remain on while the batteries symbols are cycled from right to left.

Do you see SOFT CHARGING icon displayed during power up?

William

 

[TooManyGizmos]

TooManyGizmos,

During power-up, the "CONDITION" and "SOFT CHARGING" icons should remain on while the batteries symbols are cycled from right to left.

Do you see SOFT CHARGING icon displayed during power up?

William

_________________________________


YES ........ william ..... Softcharge icon does show during power-up -goes away at end of self-test.

But the words chrge complete over the 3rd and 4th batt icon don't show on power-up - all others do. the display dont light up on power up so its hard to read- but thats what it says. What does this indicate ?

The lettering on this display is too tiny to read - especially when it's not lit up during power-up.


_____________


________________________

 

[bcwang]

I just checked mine and the words "charge" and "done" do appear over every slot during the self test. Sounds like you have something wrong with yours, maybe the "soft charge" button is broken.

 

[bcwang]

TooManyGizmos,

Have you found out what the problem with your charger is yet?

 

[TooManyGizmos]

It's broke .

willchueh , in a PM , suggested I return it to MAHA for a replacement which is what I'm doing. Soft charge just stopped working after 3 weeks

 

[bcwang]

I found a review of the 801D which is pretty much the same as the 808M except it can only take AA/AAA cells. It confirmed the same thing I found, the completeness of charge is not as good as the C204W. Here's the link for anyone interested in reading it. http://www.imaging-resource.com/ACCS/C801D/C801DA.HTM

If Tom is getting such good completeness of charge results (comparitively speaking) with the 808M, I wonder if the C204W would top the charts.

 

[TooManyGizmos]

It's broke .

willchueh , in a PM , suggested I return it to MAHA for a replacement which is what I'm doing. Soft charge just stopped working after 3 weeks

________________________________________________

I contacted MAHA by phone.

They promptly sent me a new charger with paid postage sticker to return broke one.

So far - so good - on new one . Time will tell . If anyting further develops - I'll post .

.

 

[picard]

cool charger. I will order it. I hope it will do the job. What kind of NIMH batteries can it handle? can it charge all types of niMH batteries??

 

[TooManyGizmos]

picard :

Yes....that's my understanding ......Type : AA,AAA,C,D-NiMh -even the new Eneloop's .


by the way , picard...........what planet are you visiting right now - how's the weather ?

Got enough gas to get home ?...............got milk ? :buddies:


.

 

[Tako]

Hello

I can understand that William is not able to discuss their proprietary technology. But at least, I want to know whether there is any maximum battery capacity limit for safe charging using this charger.

For instance, If you use Negative Delta V cufoff technology to finish charging of NiMH cell, at least you need to have 0.33C charging current (for instance 3.3Ah for 10,000mah D cell battery) , but this charger has just only 2Ah .(of course he has already mentioned that this charger has a lot more complicated algorithm than Negative Delta V.)
If the charging current is too low compared to battery capacity (like charging 15,000mAh D cell with 2Ah charging current), I guess almost impossible to detect cutoff point without using a timer cutoff. (From my understanding, the impossibility is not matter of charger resolution, just matter of battery behavior with such low charging current(2Ah) itself. OR if there is other way to detect cutoff point, please let me know.)

So, what do you think that charging large capacity D cell such as 12,000mah or much larger capacity NiMH cell without having timer cutoff ?
Is it really safe? (With bad luck, endless charging?)

Anyone, please answer my question.


Thanks.

If I have a lot of mistake in grammar, I apologize your inconvenience.