Lihtium ion cells getting hot

[amadeok]

Hello,

I got 12 18650 lithium ion cells from aliexpress that claimed to be capable of 30A,

I connected 2 in series and applied 6.3A of load with 4 lamps and after around 5-7 minutes the batteries reached almost 55 degrees celsius, i had to stop it because the batteries were reaching 3v, but looking at how fast the temperature was rising i think they would easily have reached 60 degrees or more.

Is this normal? Should i request a refund?

thanks
edit: i also didn't use any flyback diode, should i have used it?

 

[Nigel Goodwin]

I think you don't understand what the specifications are - assuming they mentioned 30A, that would be a short time peak, not continuous current.

I would expect the batteries to get hot, and not last very long, if you're hammering them at 6.3A.

What are you trying to do?, and what have mosfets got to do with anything?.

 

[alec_t]

Why do you want MOSFETS in series?

 

[amadeok]

Hi
thanks for replies. No sorry that title was for another post. I corrected it. I got 12 of these to make a 6s2p 24v battery pack for a e-bike with a 24v 895 dc motor, which draws 1A with no load, but it's rated for 10-20A. It's quite a small motor, but it should have a maximum torque of 10kg.cm
I understand that the fact of having the six cells in paralel with the other 6 should help with temperature

 

[amadeok]

I've just been told by the seller that the maximum continuous discharge current of the battery is 10A. The maximum peak current is 17A. Can this be?

 

[Visitor]

15 seconds of searching found this, so I don't think that spec is out of line.

 

[Pommie]

Assuming your cells are real cells and a decent capacity - 3000mAh. If you discharge them at 10A and your configuation is 6s2p then they will last about 6/10*60=36 minutes. If you discharge at 20A then 18 minutes. Is this what you expected? Is 200-400 Watts normal battery drain?

Mike.

 

[amadeok]

Assuming your cells are real cells and a decent capacity - 3000mAh. If you discharge them at 10A and your configuation is 6s2p then they will last about 6/10*60=36 minutes. If you discharge at 20A then 18 minutes. Is this what you expected? Is 200-400 Watts normal battery drain?

Mike.

Hi,
Them lasting 36minutes at 10A or less than that was the secondary concern, what i'm concerned is that drawing 10A from them at any amount of time seems to overheat them too much, which could cause them to get damaged or maybe even catch on fire.

 

[Pommie]

Sounds like you bought fake cells. What do they (each) weigh?

Mike.

 

[audioguru]

AliExpress sells cheap Chinese clothing and shoes. Their batteries are no-name-brand and are probably used or fakes.

 

[simonbramble]

I bought a load of 18650 batteries on line and indeed they were fake. As Pommie says, the best way of telling is to weigh them. I actually wanted duff cells as I was testing a battery balancer circuit and fake cells go out of balance a lot quicker. They were about 1/5th the weight they should have been. ebay and most Chinese supplier are famous for selling counterfeit products

 

[audioguru]

Here is one of the many videos about fake 18650 batteries: