18500 Li-ion heated up during charging

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DB Custom
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18500 Li-ion heated up during charging

Hi everybody, just a question to confirm what I’m thinking on this one. I was charging an 18500 Li-ion 1800mAh capacity protected cell from TrustFire and it got quite warm, they usually always stay cool during charging. This cell needs to be disposed of, right? I was using a cottonpickers USB charger with voltage monitor at 700mA when it got hot.

I have a pair of them that I have in a light my 5 year old son uses. Already got a new pair, this time AW’s from Lighthound…also protected 18500’s but with 1500mAh capacity. Being as how it’s in my son’s light, any question at all as to the cells integrity and it’s outta here.

Just checking in that this is the correct approach.

I only have 2 10440s from Ultrafire that aren’t “name brands” after this, everything else is Panasonic, AW or Redilast.

Thanks for input on this, never had one heat up before but I’ve not been into these kind of lights for very long either. My first Li-ions were purchased for a MagLite mod, a one cell from JayRob that I’ve had about a year, with my first cells being from Novae…32650 protected at 5500mAh. I have 6 of those and they’re all doing well.

scaru
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Yeah, that definitely isn't supposed to happen. It could come from two man things. 1st, if the cell is an extremely low capacity and the charge current is to high (unlikely in this case) or 2nd if the internal resistance of the cell is to high. From the sounds of it it is option 2, which will only get worse as more time passes. It also means that it is not going to supply as much power when used in a flashlight. 

texaspyro
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scaru wrote:

Yeah, that definitely isn’t supposed to happen. It could come from two man things. 1st, if the cell is an extremely low capacity and the charge current is to high (unlikely in this case) or 2nd if the internal resistance of the cell is to high. From the sounds of it it is option 2, which will only get worse as more time passes. It also means that it is not going to supply as much power when used in a flashlight. 

Or 3) the charger is bad …

moderator007
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Did the charger report a full cell? Whats the voltage of the battery?

ohaya
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Do you have a meter, so that you can check the battery voltage?

DB Custom
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The charger is working fine, charging other cells with no issue. The 18500 in question is 1800mAh capacity and was being charged at 700mA. So it wasn’t being charged at too high a rate.

The charge was in progress when I terminated it due to the heat issue. The voltage monitor was reporting something like 4.15 when I took it off the cell and it now shows 4.08.

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Could it be that anyway? I mean, the charger is a USB charger so it could only pull some 1200mA from the USB port even if the charger went bad…being that it gets it power from the computer USB port it simply can’t provide enough total output to overcharge a 1800mA cell, can it?

At any rate, I’ve used the charger on another cell and it worked fine. Should I keep my eye on this charger to be on the safe side? I always charge the cells right here on the computer beside me and if I have to leave the computer I unplug it and restart it later rather than leave it.

ohaya
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Hi,

How long was it between when you took it off the charger, and then measured that 4.08V?

I’m kind of thinking that you should check the voltage, maybe tomorrow, to see if it is maintaining the voltage.

You could also try measuring the current while it’s charging that 18500 also, i.e., set the charger to 700 mA charge rate and measure current to see if actually is charging 700 mA. I remember seeing page showing how to do that, by putting two pieces of aluminum foil with a piece of paper between them, then attach your meter (current mode/connection) leads to each of the aluminum pieces.

I don’t have an explanation for the warming up. Then again, I’m still a newbie (BTW, how long do I get to say that :)?)…

Edit: BTW, for a USB 2.0 port, maximum current is ~500 mA. Hmm. Maybe try setting your charge rate lower, to maybe 500 mA, and see if that battery still warms up when charging it?

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DBCstm wrote:
The charger is working fine, charging other cells with no issue. The 18500 in question is 1800mAh capacity and was being charged at 700mA. So it wasn’t being charged at too high a rate.

The charge was in progress when I terminated it due to the heat issue. The voltage monitor was reporting something like 4.15 when I took it off the cell and it now shows 4.08.


From that much voltage drop in a short amount of time, I would say toss it. But the cell would have dropped some voltage right off the charger even if new. I suspect if you measure it in a day or two it will be even lower. Let it rest a day or two and measure again. Let us know what its voltage is then. But I do suspect its shot. As scaru already said, the internal resistance is probably what is causing the cell to build heat while charging.
ohaya
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moderator007 wrote:
DBCstm wrote:
The charger is working fine, charging other cells with no issue. The 18500 in question is 1800mAh capacity and was being charged at 700mA. So it wasn’t being charged at too high a rate.

The charge was in progress when I terminated it due to the heat issue. The voltage monitor was reporting something like 4.15 when I took it off the cell and it now shows 4.08.


From that much voltage drop in a short amount of time, I would say toss it. But the cell would have dropped some voltage right off the charger even if new. I suspect if you measure it in a day or two it will be even lower. Let it rest a day or two and measure again. Let us know what its voltage is then. But I do suspect its shot. As scaru already said, the internal resistance is probably what is causing the cell to build heat while charging.

Hey Moderator… Isn’t that what I just said?

JUST KIDDING :)!!

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Ok, so how do I check the charger input if it’s connected by magnets on leads? Are you saying to connect my DMM on either side of the positive contact in such a way that the input is running through my DMM? This would be with the DMM set to Amps?

The charger is a Cottonpickers charger, with built in digital voltmeter and 2 output selections…480mA and 700mA. I have another with 90mA and 200mA settings.

Edit: On 700 my DMM shows .53, on 480 it shows .39 This going into an NCR18650PD Panasonic cell

moderator007
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Hook the DMM up if it was another cell in series with the battery, set DMM to current. The current has to run through the DMM.
I really don’t think its the charger. The current readings above are perfectly acceptable.

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My DMM has given me false readings when taking tail measurements in the past looking to see what amperage a light is pulling. I finally got readings that are close to what others get by using 12ga solid copper leads about 2 in long. I just set it up like that and took the magnet out of the alligator clip on the positive end of the charger, clipped it onto the red lead in the DMM with the the negtive magnetic alligator clip on the negative end of the battery. I held the black lead of the DMM to the positive side of the battery and plugged in the charger and got that .53 reading when the charger was set on 700mA.

So my DMM is off, or my computer is not allowing the charge to output more than 500mA or the charger is not functioning properly.

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Was the battery almost discharged when you measured the current. If the battery voltage was high (almost fully charged) towards the end of the charge cycle the current would be lower when the charger hits the constant voltage stage.

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Ah, forgot about that…no this cell had 4.05 when I put it on the charger and the charger was showing 4.14 going in. That might very well account for a lower amperage charge rate.

Thanks for reminding me. I’ll have to run something down before I can get that true reading.

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As long as the voltage wasn’t 4.2v while charging, the charger shouldn’t have hit the constant voltage stage yet. At least my hobby charger doesn’t. The cottonpickers charger may be different.

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Charger is just fine in the output dept, a 14500 cell with 840mAh capacity at rest @ 3.68V tested at the 700mA setting with the DMM showing .70, with an alternating .69 and back to .70.

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Charger is fine then. Interested to see the voltage of the problem cell once it sets for a day or two. I suspect it will be well under 4.0v

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The “problem cell” is still sitting at 4.08V. That was Wednesday night late when this happened, and it’s still sitting at 4.08V The charger, however, is daid! I noticed the illumination indicating charge dimmed a few times during the charge cycle so I pulled it off the charger and checked magnetic leads on the cell I was charging. Pulled the lead connection from the charger and put it back, all seemed well. Even flicked the amperage selector switch a couple of times. The charger now does nada, zilch. The display works fine, but no charging lights no matter what I try.

I contacted Cottonpickers and he’s sending out a replacement, virtually no questions asked. (virtually because he asked my mailing address to send a replacement out to)

I was wondering if it could be fixed, but then, it’s embedded in epoxy.

So now I don’t know if the cell should be tossed or not. It did get pretty dang hot, uncomfortable to hold but not impossible to hold.

A good testimony for customer service at Cottonpickers though, he’s all over it! Smile

ri chevy
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DBCstm wrote:
Hi everybody, just a question to confirm what I’m thinking on this one. I was charging an 18500 Li-ion 1800mAh capacity protected cell from TrustFire and it got quite warm, they usually always stay cool during charging. This cell needs to be disposed of, right? I was using a cottonpickers USB charger with voltage monitor at 700mA when it got hot.

I have a pair of them that I have in a light my 5 year old son uses. Already got a new pair, this time AW’s from Lighthound…also protected 18500’s but with 1500mAh capacity. Being as how it’s in my son’s light, any question at all as to the cells integrity and it’s outta here.

Just checking in that this is the correct approach.

I only have 2 10440s from Ultrafire that aren’t “name brands” after this, everything else is Panasonic, AW or Redilast.

Thanks for input on this, never had one heat up before but I’ve not been into these kind of lights for very long either. My first Li-ions were purchased for a MagLite mod, a one cell from JayRob that I’ve had about a year, with my first cells being from Novae…32650 protected at 5500mAh. I have 6 of those and they’re all doing well.

I do not think that an 18500 Trustfire cell puts out 1800 mAh’s. The *****.fire cells are consistently overrated. Just another *****.fire battery issue. I see that you have figured out the charger troubles. You should be better off with the AW cells. And for the record, Cottonpicker is an excellent vendor to deal with. Big Smile

moderator007
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I agree. I couldn’t find a true capacity test done on a 18500 trustfire. From trustfire’s reputation, I would guess to say 1200mah to 1500mah maybe the true capacity. Maybe someone that has tested them can chime in.

ohaya
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I’ve been following this thread. So, at this point, there’s still no conclusion about why the battery got hot? Could whatever caused the charger to die have been the reason for that? While you’re waiting do you have another charger that you can try the battery in?

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Ohaya, the cell is at 4.08V so I’ll have to take a chance and run it down in something before trying again to charge it. I don’t have anything but my son’s small light that it fits in, so do I want to take the chance or don’t I? The light it goes in has an XP-E in it with Lo-Hi-Strobe modes, so I’m going to guess that on Hi it’s pulling something South of 1.5A so I’d have to run it on Hi for an hour or more to discharge it enough to get a true test on charging.

We’ll see. I’ve got to get some NiMH’s and camera batteries charged up for a shoot tomorrow, might run this little light 5 or 10 minutes at a time while I’m taking care of all those and see if I can get it down to 3.6V or something.

Will let y’all know how that goes later this evening. Been out mowing all morning, still not done with that but have to get my camera gear ready to go so I guess the backyard acre can wait.

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Sorry, had to take a break…a 16” Papa Murphy’s Family size Rancher was cooking up some amazing smells! Smile
DBC_April 20, 2013_123548

I ran the light for about 30 minutes, sitting on top of a copper bar that was in turn on top of a 3” cube of aluminum. Never got the least bit warm even. But an interesting development. The voltage sagged a lot quite fast but would spring back up when the load was removed. Yes, I’m checking it periodically and sitting right in front of it…touching it to check for heat. When I left it to go eat it was down to 3.56V after only about 25 minutes total run time. When I came back from eating it was back up to 3.9V.

So it would seem to be compromised. I’m planning to get it down to around 3.6V at rest, then see how it charges back up. The charger that has quit is a 400-700mA unit, the only other way I have to charge is an UltraFire 188 with 300 or 650mA settings or a much smaller output cottonpickers for the small cells. I’ll use the larger UltraFire and see how that goes. Might test the cell like this again.

ohaya
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Hi,

How much was “a lot” (when voltage decreased under load)? It sounds like the internal resistance is high, which would account for the voltage under load dropping (I gather that “internal resistance” can be modelled as a resistor in series with the voltage source, so higher current under load would mean a larger voltage drop across the internal resistance ==> lower output voltage under load).

Jim

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Jim, it dropped from 3.58V to 3.35V in 10 minutes. I took the rested cell at 3.9V and ran it in the light about 15 minutes and it was back down to 3.58V. Put it back in and ran it that 10 more minutes to 3.35. It will climb back up most of the way in the next 5 minutes at rest. I waited while typing this and it’s now back up to 3.59V. Crazy stuff.

Edit: I tried it in my HD2010 with XM-L T6 and 3.04A driver, it would run Hi for about 3 seconds then drop to med.

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The cell has a high internal resistance which causes the voltage to drop under load… time to recycle it.

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With an outdoor temperature probe taped on the cell in the UltraFire 188 charger, 45minutes into the cycle I’m getting a 103ºF reading in a 74ºF room. Definately warmed up but again not so much that it can’t be held. But normally, none of my cells warm up at all. So 28º over ambient is an event! And this when the charging rate should be very low as the cell charge is near completion. It was warm earlier but I finally got the idea to pull me temp probe from outside and put it on the cell, don’t have any other way to measure the temperature.

I know this is abnormal, but is it bad?

Pulled it and checked the voltage, after 50minutes at 650mA it’s only at 3.93V and pretty dang warm! My kids Temporal scanner Infrared thermometer got 107 at about a 1/4” away, after pulling the cell and using the digital thermometer in direct contact it over runs it’s capacity and just says “HI”.

Methinks this one has a date with the recycle bin.

Edit: for reference I scanned the aluminum battery tube of the host flashlight laying empty on my bed. The Temporal Scanner says 74.8ºF and my digital thermometer on the wall says the ambient inside temperature is 74.2ºF.

texaspyro
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DBCstm wrote:
after pulling the cell and using the digital thermometer in direct contact it over runs it’s capacity and just says “HI”.

That’s a very friendly thermometer. Mine just says “you gonna die!”.

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Anything over 86°F is considered elevated temperature for a li-ion. Its not worth the risk, the rise in temperature should only get worse with each cycle. Time to toss, before something goes bad wrong.