# How long to charge a new batteries (14500 and 18650)?



## ohaya (Mar 15, 2013)

Hi,

I'm kind of new here, but I got in a 14500 and 18650 battery this week, and just got a new Trustfire TR-003 charger.

- 14500: EagleTac 14500 - 750 mAh
- 18650: EagleTac 18650 - 3100 mAh

I got the batteries first, a couple of days ago, and measured their voltages, and they both measured about 3.9V. I didn't use much, just to test them in some lights, probably just a few minutes each.

Then I got the charger today, so I put both batteries into the charger about 6:00 PM. It's now about 10:30 PM here, and the two lights on the charger for those bays are still red.

Neither the batteries nor the charger is getting hot, actually they're barely warm.

I followed HKJ's guide to test the charger, the aluminum foil on the contacts thing, and the voltages on both bays are about 4.2V.

This is the first time I've charged lithium batteries, and first time with this charger, so I was wondering if it's normal to take this long to fully charge the batteries? 

Thanks!

Jim


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## ohaya (Mar 15, 2013)

Hi,

Spoke to soon. The light for the bay that the 14500 battery was in turned green just after I posted the post above .. Measured the battery after taking it out and it's 4.23V. Is that ok?

So, it took ~5 hours to charge the 14500 from a new/unknown state, and that's just a 750 mAh battery. 

I wonder how long the 3100 mAh 18650 will take (the TR-003 specs say 500 mA, so, shouldn't it have been done by now, even if it was pretty much depleted?

Hopefully I won't have to stay up all night for this (don't want to leave the battery in the charger unattended )!

Jim


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## ohaya (Mar 16, 2013)

Hi,

For the record, at about 8 hours 50 minutes, I measured the 18650 battery voltage at 4.21V, but the light on the charger was still red. It's late here now (~02:50), so I removed the battery from the charger, rather than leaving it charging, because I couldn't/didn't want to wait longer, and it's off for some sleep now. 

Sigh... I can picture myself babysitting batteries from now on ... BTW, I noticed that the card that came with the charger has, in big, bold letters, "NO SUPERVISION NEEDED". Right !!

It definitely does charge the batteries, but I'm not sure if I trust it to terminate/cut-off at the proper level yet...

Jim


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## yvonne_chan (Mar 16, 2013)

The charger won't cut off itself. But the light will show green when the battery is full charged.IS you battery protected or just a cell? I mean, does it have a pcb？ If not, I think you'd better be careful during charging because the function of a pcb is to protect the battery from over-charge.


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## ohaya (Mar 16, 2013)

Hi,

The batteries are protected type.

BTW, changed my mind and put the 18650 back in, thinking it would turn green shortly, because I really want to find out when the light turns green what the battery voltage will be.

That was over an hour ago ... Still red.

Jim


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## ohaya (Mar 16, 2013)

Hah! The light just turned to green!

So that was approximately 10+ hours for the 18650.

I measured the battery voltage after that, and it was 4.24V.

Jim


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## SilverFox (Mar 16, 2013)

Hello Jim,

It looks like the claim of supplying 500 mA of charging current may be a little "optimistic." 

A very general rule of thumb on charging Li-Ion cells is to take the capacity of the cell and divide it by the charging current. This will give you hours. The CCCV algorithm tapers the current off after the cell reaches 4.2 volts so you have to add some extra time to the charge time you first calculated.

At a 1C charging rate it takes around 1.3 to 1.5 hours to charge the cell. Note that a 1C charging rate is charging at a rate that is equal to the capacity of the cell. If the cell is 3100 mAh in capacity, a 1C charge rate would be 3100 mA. 

As you reduce the charging rate, the multiplier also drops. An example of this would be if you charged your cell at a 0.2C charge rate (3100 mAh X 0.2 = 620 mA) the charge time should be around 1.1 times the time calculated. Using 620 mA as a charging rate for this example, you would expect the cell to be fully charged (from empty) in 300 minutes, but then you have to multiply that time by 1.1 and you end up with a charge time of 330 minutes. 

Understand that these are very general guidelines and are not exact. It gives you a time frame to work within so you can attend to your charge and still live your life. For example, when I start charging a cell I also start a countdown timer. I set the time on the timer according to what my "best guess" is of what the charge time will be. If I get distracted the timer reminds me that I have a charge going. I happen to use a Talking Timer so it also lets me know frequently how much time is left on the charge. This usually keeps me from getting totally distracted. I tend to set the timer a little short of the calculated time. Most cell issues occur near full charge so I want to make sure I am close by as the charge finishes.

Since you are just starting out I will also mention that it is a good practice to set the charge on a surface that is heat resistant and think ahead to what could possibly go wrong. If the charge melts down a few moments taken ahead of time placing the charger on a tile can go a long way in limiting any damage. As you know, heat usually proceeds "issues" so it is a good practice to touch the cells during the charge to check for heat.

And that wraps up this session of

The "Charge" of the Light Brigade...  

Tom


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## ohaya (Mar 16, 2013)

Tom,

Thanks for the tutorial!

A couple of questions:

1) Where does that "1.1" factor come from, i.e., how is/was it derived?

2) This 18650 battery was new, I had just received it earlier this week, and I didn't do much with it, basically just put it into a light and turned it on a couple of times and marvelled at how bright it was, plus measured the voltage, which as ~3.9V originally. Since the battery initially showed some voltage (3.9V), I'm assuming that means that it had some charge in it, say it was "x" mAh at that point. Then I got the charger yesterday, and at about 6:00 PM, I started charging the 18650. Say the battery's real capacity was actually 3100 mAh. If that was the case, then would your calculations be based on "3100 - x", rather than on 3100?

In other words, say the battery arrived partially charged, with 600 mAh, so then the approximate time to charge would be based on 3100-600, or 2500. Is that correct?

So then, say the actual charge current was as advertised, 500 mA. Then, the estimated charge time would be 2500/500, or 5 hours, and then you apply the 1.1 factor, to get the final estimate of 330 minutes or 5.5 hours.

Is the above all correct, at least in principle?

3) So, #2 seems to indicate that the charge current is not 500 mA (.16C), which is what I think that you were saying, right? 

4) As I reported, I was actually two batteries, the 14500 and the 18650, for 6 hours, and then removed the 14500 when its light turned red. What I'm thinking is that the charger may've been splitting the 500 mA charge current between the two batteries during the time they both were in the charger. 

So, suppose that was the case. That means that for the 1st 6 hours, the charge rate was 250 mA, so at 6 hours, about 1500 mAh went "into" the 18650, so there would be somewhere between 1000 mAh (2500 - 1500) and 1600 mAh remaining to be charged (again, all estimates only).

So, when I removed the 14500, how long to charge the 18650 the remaining way (1000 mAh - 1600 mAh) @ 500 mA? That looks like it should be somewhere between 2 - 3.2 hours, which should have taken me to 8:00 PM - 9:00 PM+, my time zone (EST).


The above are all just "theory", but I was wondering if the above calculations are correct, at least in principle? 

Thanks,
Jim


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## ohaya (Mar 16, 2013)

Tom,

P.S. Re. the other things you recommended:

1) Surface: I had the charger on our kitchen countertop, which is granite. I probably should put something under the charger, so that if something bad happened, it wouldn't mess the countertop up, or put it somewhere else completely, with something inflammable under it.

2) As I mentioned earlier in the thread, I was checking both the charger temperature and the batteries' temperature intermittently "by hand". Neither the batteries nor the charger got even to "warm". Also, I think that the TR-003P4 is suppose to have temperature protection (although I don't see any sensors).

Jim


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## HKJ (Mar 16, 2013)

I cannot say much about the TR003 charger, but you can check my website for charge time with different chargers and how much time is spend in CC and CV phase.

The VP1 has curves for 0.25A, 0.5A and 1A charge current.


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## Top Cat (Mar 16, 2013)

You might take a measurement of the actual mA you charger is putting out at the voltage in use, and you will get a better picture of what is actually going on. I've seen similar chargers rated at 250 mA, but the actual output can vary from 6-103 mA, or whatever at full power cycle.

The Chinese tend to view published specifications as more an aspect of sales rather than science. 

Witness their XML flashlights are up to 2200 lumens now...


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## ohaya (Mar 16, 2013)

Top Cat (et al),

The charger was reviewed here:

http://www.candlepowerforums.com/vb/showthread.php?319755-Trustfire-TR003P4-18650-Charger-Review

and according to that:



> With a 18650 @ 3.16v the 4 bays returned - 0.63A - 0.65A - 0.67A - 0.67A
> 
> 18650 @ 3.52v the 4 bays returned - 0.55A - 0.53A - 0.53A - 0.56A
> 
> ...



and, if I'm reading that correctly, the charge current decreases while charging.

The starting battery voltages that I measured were in the 3.8V - 3.9V range, so interpolating the above, the charge current seems like it'd be more like mid-100 mA and lower, so that's probably why it's taking so long ...

I just got another pair of EagleTac 14500s/750 mA batteries (yes, I've been buying a few lately ), and put them in the charger about 5:00 PM today. 

Starting voltage for the batteries was about 4.84V, and it's now about 8:30 PM here (so about 3.5 hours have past). 

I just measured the voltage now, and they're at 4.20V, and the light is still red on the charger.

I'll post back when the lights turn green.

Jim


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## BellyUpFish (Mar 16, 2013)

Just charged my first set of Fenix 2600mah 18650's. Less than 3 hours to get two green lights.


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## ohaya (Mar 16, 2013)

Hi,

The lights for both batteries just went green a couple of minutes ago, so about 9:05 PM, so charge time was about 4 hours.

I measured the voltages for both batteries after charging. One was 4.15 V, and then other was 4.22 V, so both are "4.2 V +/- .05V".

Jim


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## ohaya (Mar 16, 2013)

Hi,

I don't know if this was the "right" thing to do, but it bothered me that one of the batteries only got to 4.15V, so I put that into the charger, hoping that it'd get a green light. It charged for awhile (over hour) but the light never turned green, so I just pulled the battery, and measured voltage, and it's now showing 4.23V. Again, the light never turned green up to the point I unplugged the charger and pulled the battery.

So, question for the next time: If a battery charges to the point the charger light turns green, should I just leave it as that, assuming the battery voltage is 4.2V +/- .05V?

Thanks,
Jim
Jim


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## SilverFox (Mar 17, 2013)

Hello Jim,

The 1.1 factor comes from actual charging experience. Start with a discharged cell and note how long it takes to charge. Do the math and you come up with an average "best guess."

The answer to your second question is yes.

To go into a little more detail...

At 3.9 volts your cell had around 65% of its total capacity. If your capacity is 3100 mAh, 65% of that is 2015. Subtracting 2015 from 3100 leaves you with 1085. Your charger would put in around 1085 mAh to bring the cell to full charge.

The state of charge is based upon resting voltage using this formula.

SOC% = 100(0.1966+SqrRoot(0.0387-1.4523(3.7835-Vcell)))

You would then take the 1085 mAh needed to charge the cell, divide it by the charge current, and finally add the extra factor in to come up with the expected charge time. If your charger is charging at 500 mA, you would expect the cell to be fully charged in a little over 143 minutes.

1085 mAh / 0.5 amps = 2.17 hours.

2.1 hours X 60 = 130.2 minutes. 130.2 X 1.1 = 143.22 minutes.

In this case with the cell partially charged the "additional" factor may be a little higher than 1.1 due to reduced time spent in the CC phase of the charge. The charge current drops off during the CV phase of the charge so your charge time increases.

Question #3, correct. I believe HJK has run some tests on that, or a similar, charger and the charge rate seems to be lower than advertized.

Question #4 is difficult to answer. Without knowing the actual charge rates and how the charger handles multiple cells it is hard to predict how long the charge will take. Your thinking in the right direction but you now need some actual measurements to fill in the gaps. 

It is good to hear that you are thinking ahead and taking precautions to prevent damage in the rare event things go wrong. 

As far as topping off goes, it is generally not a good idea for Li-Ion cells. Save that for when you anticipate needing every mAh of capacity you can get. For example while backpacking you only carry limited spares so that would be a good time to push things a little and try to get the voltage of the cell as close to 4.2 volts as you can. In a higher current draw light this extra capacity may not amount to much run time, but in a low current draw light it may give you a minute or two of extra run time. Overall it is usually not worth the effort.

Tom


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## HKJ (Mar 17, 2013)

SilverFox said:


> The state of charge is based upon resting voltage using this formula.
> 
> SOC% = 100(0.1966+SqrRoot(0.0387-1.4523(3.7835-Vcell)))



That formula is probably valid for a very specific chemistry, but the actual chemistry varies between different batteries, because the manufacturers tries to optimize them.

I have done some testing with a couple of batteries and made SOC tables for them.


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## SilverFox (Mar 17, 2013)

Hello HKJ,

That is correct. I believe the formula came from a Sanyo publication a few years back. If I remember correctly the discharge rate used to derive the formula was 500 mA and I believe the resting time was 30 minutes.

I find it interesting that your data shows 63%, 73% and 75% at a voltage of 3.9 volts depending upon the cell being tested.

All in all as a rough guess 65% is reasonably close as an estimating tool.

Tom


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## ohaya (Mar 17, 2013)

Hi,

An FYI: Something interesting about the TR-003P4 behavior (to me, at least ): 

I had a 14500 (EagleTac 750 mA) that I charged on this previously, and had the 14500 in a light, which I finally used today for awhile, maybe for about 20 minutes.

I measured the voltage after that, and it was down to 4.02V, so I figured I'd throw it into the TR-003. So, I put it into the charger, then plugged the charger into the AC, and all lights came up green.

Hmm. 

I tried that a couple of times, and it did the same thing every time.

So, I pulled the battery out of the charger, then plugged the charger into AC, THEN inserted the 14500 battery into the charger (i.e., after the charger was powered on), and then the red light came on. 

That was at 6:34 PM EST, and it's charging now (still).

I'm assuming that the reason that it wouldn't charge earlier was because the charger detected (thought that) the battery as being already "fully" charged, but I'm wondering, why would it behave differently when I inserted the battery after the charger had already been powered on?

Sorry for all the questions.

Thanks,
Jim


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## ohaya (Mar 17, 2013)

SilverFox said:


> Hello Jim,
> 
> The 1.1 factor comes from actual charging experience. Start with a discharged cell and note how long it takes to charge. Do the math and you come up with an average "best guess."
> 
> ...




Tom,

A couple of questions:

1) I guess that there might be a couple of different versions of of "topping off"? For example, I guess I understand that it was probably not a good thing to do what I did last night, putting the battery that ended up at 4.15V after charging back into the charger immediately. 

But, in the case like post #19, where I've used the battery for awhile already, and want to bring it BACK up to full charge, it seems like charging the battery would be a good thing, i.e., "avoid discharging too much (< 2.5V?) and avoid charging too much over 4.20 V"?

2) Now that I DO have the battery back in the charger, and know the start time (6:34 PM) an pre-charge starting voltage (4.02 V), could what you said in #16 (an quoted above) be used to "reverse engineer" and find that "factor" precisely?

Thanks for all of your help!

Jim


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## ohaya (Mar 17, 2013)

Hi,

Green light just came on with the 14500, so:

Started: 6:34 PM, 4.02V
Ended: 11:55 PM, 4.22V

Charge time: 5:21, voltage delta: .20V.

This is for an EagleTac 750 mAh 14500.

Jim


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## SilverFox (Mar 18, 2013)

Hello Jim,

The distinction between topping off and charging is gray...  

Yes you can reverse engineer things, but be sure you know what you are looking at. The last part of the charge takes a long time because the charge current keeps going down while the voltage is held constant. If you find a factor for that portion of the charge (say from 4.0 volts to 4.2 volts) it may not apply to a full charge (say from 3.5 volts to 4.2 volts). 

If you ran enough tests you could determine a factor for each 0.5 volt increment. However, this level of precision is usually not needed. 

Tom


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## ohaya (Mar 18, 2013)

Hi Tom,

Thanks. I was kind of thinking that that (varying charge current) would be the situation.

Jim


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## PapaLumen (Mar 18, 2013)

I wouldn't be that happy about it charging to 4.24 even though its within spec. None of my chargers go over 4.2v. I have a hobby charger and a Xtar wp6 that does 6 cells and charges them all to about 4.18v. 

Maybe you could try an Xtar WpII for two cells.? I think most on here are happy with that charger or if you have deep pockets then a Pila charger gets very good reviews but very pricey for what it is.


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## ohaya (Mar 18, 2013)

Hi PapaLumen,

I think others have mentioned that the terminating voltages that I'm seeing with the TR-003P4 may be in spec, but a bit on the high side. As I responded earlier, I'm just getting started, and just got the TR-003P4, like last week, so I don't really want to get another charger immediately, as long as I don't do something unsafe. 

I see some new chargers coming, like the VP1, which are out, but apparently impossible to get now (I saw one Ebay for *$999*!), and some mystery charger that I saw that HKJ was suppose to be reviewing, so I figured that can learn while I wait. 

I don't mind so much accumulating flashlights, but not so much accumulating chargers ...

Thanks for the suggestion though.

Jim


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## PapaLumen (Mar 20, 2013)

Fair enough, no-one likes to rebuy after a week. I have a couple of DX chargers that I wont use any more so I guess I'm accumulating chargers lol. Just didn't know about chargers when i bought them.


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## ohaya (Mar 20, 2013)

PapaLumen said:


> Fair enough, no-one likes to rebuy after a week. I have a couple of DX chargers that I wont use any more so I guess I'm accumulating chargers lol. Just didn't know about chargers when i bought them.



I have the same excuse ...

Jim


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## Fresh Light (Mar 20, 2013)

I purchased the xtar sp2 today. I think it may be the best charger available for the widest range of different cells. .5, 1, and 2 amp charging for various sizes. The main omission is LiPo support. If they made a 6 cell charger with display like the VP1 and had charging capability of the sp2, well that would be probably be the best of all worlds.


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