One of 2 batteries seem to heat up while vaping

I have a reuleaux rx gen3 dual, i use 2 lg batteries on it. Usually vape on about 50w with a v8 baby beast on it. The batteries were used on a single battery mod for a very few charge cycles before. It usually shows one battery being lower by one bit on the mod's display. It probably happened from when i started using this double battery mod, but i recently noticed that the side that shows lower battery heats up while taking a hit. I suppose the batteries are not really married very well, even tho i charged and discharged these batteries a few times. Could it be a defective battery ? The batteries themselves look fine visually and are practically new. Couldn't really find much on this problem while searching. Would it be ok for batteries to be left charging overnight to maybe bring them closer in voltage, because i suppose the mod would cut of the charging to prevent overcharge ?

There are many things that can cause this. How are you charging the batteries? Does the issue move if you change the battery order? Does the battery fully charge? Have you tested it with a proper volt meter after it reads fully charged?

Might be a bad battery wrap?
Might be a bad battery?
In nearly 4 years of vaping I have had 1 25R and one HG2 go bad soon after new.
The rest held up 3+ years. Recently replaced all my old cells. They were giving noticeably shorter run time per charge.

Replace both batteries with new ones as a pair. Leave them paired together for their lifetime to prevent this problem. If the problem should still occur after this, replace the mod.

Batteries heating is NEVER a good thing!

i charge them through the mod. Don't have an external charger nor a voltmeter on hand. The wraps looks basically mint. the issue does move if i swap the batteries in the mod. the batteries do fully charge. gonna try to charge overnight maybe, report tommorow.

xdomisx said:

i charge them through the mod

Click to expand...

Ahh that is likely your problem as very few mods actually charge both batteries the same.

I only recommend charging in the mod for occasional use.

i had a similar problem
one battery always took longer to charge than the other
i tracked it down eventually to a crappy nitecore I4 charger ( probably a fake )
.. i took the voltages before and after use each and every time .. recording each side and each battery ( i have 2 matched pairs )
when i went to a charger i thought was a substandard type ( vontar vt2 plus ) the problem disappeared ( turns out its a really good one )
it stops charge at 4.19 volts and now each battery in the same set takes the same time to charge and the voltages stay equal

so my advice .....
get an external charger ( all the experts will tell you that .. mostly gooch )
and a cheap(ish ) multi meter
both small prices to pay to keep your mods and person safer
and your batteries will last longer