18650 getting very, very, very hot.

[Oscar_Muffin]

First of all I'd just like to say hi to everyone and please don't beat me up for using the wrong terms or explaining things in vague ways as I'm relatively new to vaping. I'm having a problem with my 18650 in a home brew ABS mod (pictures to come). I was sat puffing away for about 5 minutes then I feel the case start to get a bit warm, I open it up and take the cell out, it was quite warm so I set it aside to cool off a little. I come back to it 5 minutes later, pick it up and it feels like it's cooled down. Then I touch the positive terminal, it was extremely hot, fearing that it was going to vent in my room I run to the bathroom and put it in the sink (which was dry).

Another thing I would just like to say quickly is that while I am new to vaping I have a good knowledge of electronics because I am on my second year of an electrical engineering course at collage.

I go back to the cell 15 minutes later and begin measuring the temperature of it using an infrared thermometer, it seems to have cooled down so I pick it up with a pair of silicone tongues and transport it to my room. Then I measure the voltage of the cell and it reads nothing, I try another multi-meter and it still reads 0. Then I measure the continuity between the positive and negative terminal, there was none. So the battery could not have been dead shorting while I was leaving it to cool off.

That was a few hours ago and since then I have been wondering why the positive terminal was able to get that hot but the rest of the cell stayed cool to the touch. I began taking some measurements of my build, the coil measures in at 0.8 ohms and the only other significant resistance which is the switch measures 0.4 ohms. Since these are in series the resistance of the entire circuit adds up to 1.2 ohms. The voltage of the battery before it died was 3.75v.

Spoiler

I proceed to bang these numbers into a calculator and I come up with 3.1 amps and 11.7 watts. Using a chart I found online I found that these numbers are well within the safe operating limits of basically any 18650. Which makes me wonder why the battery was getting so warm in the first place and why the positive terminal burned my hand. During this investigation I measure the voltage of the "dead" battery again. It had suddenly come back to life and is reading 3.7v although I will not be trying to use it again.

I'd like to know if anyone knows what's going on here? It's certainly something I've never encountered before and hopefully won't encounter again.

 

[AzPlumber]

A picture of the battery would be helpful

 

[Oscar_Muffin]

A picture of the battery would be helpful

Was just about to do that, not really much to see though.

 

[Izan]

only 6 wraps? is it a 5mm mandrel? I think you may be closer to .4Ω then .8Ω.
Gonna guess the battery is not up to the task.

 

[Oscar_Muffin]

only 6 wraps? is it a 5mm mandrel? I think you may be closer to .4Ω then .8Ω.
Gonna guess the battery is not up to the task.

I've checked it by just straight up measuring the resistance. Then I checked it by measuring the voltage of the battery, putting the multi-meter in series and measuring the amps. It all works out to the coil being 0.8.

 

[edyle]

my guess it was a protected battery.
protection circuit cut you off.

your mod probably has a short.

 

[edyle]

If your switch has 0.4 ohms and your coil has 0.8 ohms, your switch is going to be getting very hot.
I guess it's going to get hotter than your coil because at least your coil gives off energy to the eliquid, whereas the switch is effectively dry burning.


Please check out Baditude's blog for battery information.
Always use high drain safer chemistry batteries for vaping.

 

[Oscar_Muffin]

A picture of the battery would be helpful

Sorry if this is coming out way too big but I couldn't re-size it. The black stuff you see near the negative terminal is just inky finger prints so don't worry about them. That small silver spec in the left picture is a little bit of exposed casing but there is literally nothing for it to short to. The entire case is plastic and all the wire's are insulated and stuck down with silicone.

 

[sonicbomb]

As no one has asked yet exactly what battery is it, I can't tell from your picture it's too blurry. But I can see what looks like damage to the wrap and 'bits' on your positive terminal. I would fathom a guess have a short somewhere, or it's a bad cell.

 

[Oscar_Muffin]

my guess it was a protected battery.
protection circuit cut you off.

your mod probably has a short.

I'm sure that it doesn't have a short. I've checked everything with the button on and the button off. Everything seems pretty much in order.

Edit: I'm not sure whether it has a protection circuit or not. It measures out exactly 65mm so I would assume not?

As no one has asked yet exactly what battery is it, I can't tell from your picture it's too blurry. But I can see what looks like damage to the wrap and 'bits' on your positive terminal. I would fathom a guess have a short somewhere, or it's a bad cell.

The bits on the positive terminal are where the cell was spot welded onto a bus bar. It came out of an old laptop battery but everything seems in order with it apart from the obvious fact that the capacity will be lower than when it was new.

 

[sonicbomb]

An old cell of unknown spec or chemistry? Stop using it immediately and buy a new one.
You need to select an appropriate cell for your requirements based on what amp CDR or mAh capacity you need.
The Samsung 25R or the LG HE2 are both really good 20 amp continuous discharge cells.

Remember ~ batteries are cheap, pain hurts, medical bills are expensive.

 

[Oscar_Muffin]

An old cell of unknown spec or chemistry? Stop using it immediately and buy a new one.
You need to select an appropriate cell for your requirements based on what amp CDR or mAh capacity you need.
The Samsung 25R or the LG HE2 are both really good 20 amp continuous discharge cells.

Remember ~ batteries are cheap, pain hurts, medical bills are expensive.

Batteries are cheap, pain makes you stronger, medical bills don't exist because I live in the UK and we have free healthcare.

I stopped using it after the sink incident anyway. Definitley take a look at those two batteries though.

Edit: To answer your question from earlier. The coil is 4mm outside diameter so probably a 3.5m mandrel or something like that.

 

[sonicbomb]

Ok cool. I live in the UK as well and I'm not sure plastic surgery to repair a broken face is covered by the NHS.
Battery awareness and safety really is paramount.

 

[edyle]

The protection circuit is usually under the positive terminal cap thing.

Laptop batteries are not recommended for vaping, and
if you plan on using lower power batteries, then you should stick to low power loads.
how bout a 2 or 3 ohm coil.

 

[classwife]

Moved to Batteries and Chargers from E-Cigarette Technical Issues

 

[folkphys]

Silly Question:
Did you remember to subtract your Multi-Meter's internal resistance from its readings of your coil and your switch? Because if you measured the switch while it was engaged, 0.4 Ohms is kind of high, and seems just the right number for a DMM's internal resistance. Plus, when coupled with your coil description.....which sounds more like a 0.2 - 0.4 Ohm coil than 0.8........

Aside: Looks like you've got an unmosfetted switch......yikes.

If you simply neglected to subtract your DMM's internal resistance, then all signs point to an overloaded underpowered battery. For example, let's say your build is more like 0.3 Ohms. This means you're drawing between 11-14 Amps frm your battery depending on its charge state/sag voltage......and my guess is that battery is only rated at < 10A CDR, but that was when it was manufactured and would thus be significantly less after heavy use.

Good luck.

 

[Baditude]

Edit: I'm not sure whether it has a protection circuit or not. It measures out exactly 65mm so I would assume not?

The bits on the positive terminal are where the cell was spot welded onto a bus bar. It came out of an old laptop battery but everything seems in order with it apart from the obvious fact that the capacity will be lower than when it was new.

Another thing I would just like to say quickly is that while I am new to vaping I have a good knowledge of electronics because I am on my second year of an electrical engineering course at college.

So, you have no idea what brand or model this battery was? Huge mistake.

You must know the brand and model number of the batteries that you use in your vaping device.

You must know whether the battery is protected or unprotected.

You must know what chemistry the battery is. Use only IMR chemistry batteries, not ICR battery chemistry. ICR batteries are not safe chemistry and usually only have no more than a 4 amp continuous discharge rating. IMR batteries are safe chemistry and may have 10 - 30 amps continuous discharge rating.

Battery Basics for Mods: IMR or protected ICR?

Deeper Understanding of Mod Batteries



Two years into electrical engineering studies apparently did not make you a battery expert yet. If you were using a protected ICR battery then you were pushing that cell over its amp limits.

 

[Robert Cromwell]

Sorry if this is coming out way too big but I couldn't re-size it. The black stuff you see near the negative terminal is just inky finger prints so don't worry about them. That small silver spec in the left picture is a little bit of exposed casing but there is literally nothing for it to short to. The entire case is plastic and all the wire's are insulated and stuck down with silicone.

Ahh are those spot welding spikes from removing a spot welded strap? Looks just like some batteries I salvaged from a laptop battery pack. They are of unknown quality and I would not use them in any device at over 15 watts. If from a laptop pack they are NOT 20 amp CDR batteries.
My batteries work fine at 8 watts in my Zmax regulated mod but I would never use them in anything at over 15 watts.
And yes I suspect as another said that the internal protect circuit kicked in.