Li-Ion battery pack with PCB gets HOT!

Lumbee1

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I just got a Li-Ion battery pack from Batteryspace.com (Li-Ion 18650 3.6 V 7200mah battery module with PCB). The pack works great but there is a PCB installed on it that gets HOT.

From the Batteryspace page:
One PCB (8.5A) installed with the battery pack and protects the battery from
  • Overcharge (>4.2V)
  • Overdischarge ( < 2.5 V)
  • Over drain ( > 8.5 Amp)
  • Short circuits
Is this normal? I was planning on shrinkwrapping the battery but I have a feeling that after extended usage it might get too hot and the possibly melt the shrink wrap.

BTW, the LED light was only running at 200mA but will be running at 1A in the near future.
 

LuxLuthor

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Lumbee1

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The cells don't get hot, the PCB does. It only happens while the battery pack is being used. I haven't had to charge it yet since it is new so I don't know if the same is true for charging it. The PCB is 1/4" x 1" and is stuck between two of the cells. The battery pack consists of three 18650's in a parallel configuration.
 

DM51

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If it is an 8.5A PCB and it is getting hot at only 200mA, there must be something wrong with it.
 

Lumbee1

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DM51 said:
If it is an 8.5A PCB and it is getting hot at only 200mA, there must be something wrong with it.

UPDATE. I thought the problem was with the Fatman. I tested it Saturday using the battery pack and after moving the trimpot, the maximum current I was able to achieve was only 200mA to the LED's. The battery was only used for a few minutes so I didn't notice if it got hot or not. I contacted George (taskled) and he agreed their was a problem but came to the same conclusion I did that it was a problem with the Fatman. I didn't even think that the problem could have been with the battery the whole time. I am going to wire up the other Li-ion battery I have to see if it has the same problem.
 

VidPro

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on this topic, but probably way over to the side. i was trying to replace a diode with a mosfet, one time (some cheap trick to reduce losses).
I KNEW that without enough voltage the mosfet gate would only trigger the mosfet partway. so there i was holding in my HAND (ouuuuucccchh) a mosfet that was half triggered, but had a few amps running through it.

so the moral of the story is: a mosfet IS very low in resistance, and triggers with little current, but like any transister it can be PART triggered, and expend much heat, as then it has very high resistance.
and
they put a heat path on these things for a reason, and the finger does not make a good heat sinc :)

umm how does this apply? When i was trying to work with huge amp mosfets, it was much harder to find ones that triggered at such low voltages, the low voltage ones , were leetel teeney parts.
The Mosfet is the transister type they use in protection and switching stuff for this stuff.
 
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Lumbee1

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DM51 said:
If it is an 8.5A PCB and it is getting hot at only 200mA, there must be something wrong with it.


DM51, you are correct! I connected up the other battery and it works fine. With it connected to the Fatman, I get 780mA (hasn't been tuned yet) and the LED's are bright. So the battery is defective and needs to be sent back to batteryspace. I connected the defective battery again tonight just to test it. The PCB got hot almost instantly and the heat continued to grow.

Thanks.
 

LuxLuthor

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VidPro said:
on this topic, but probably way over to the side. i was trying to replace a diode with a mosfet, one time (some cheap trick to reduce losses).
I KNEW that without enough voltage the mosfet gate would only trigger the mosfet partway. so there i was holding in my HAND (ouuuuucccchh) a mosfet that was half triggered, but had a few amps running through it.

so the moral of the story is: a mosfet IS very low in resistance, and triggers with little current, but like any transister it can be PART triggered, and expend much heat, as then it has very high resistance.
and
they put a heat path on these things for a reason, and the finger does not make a good heat sinc :)

umm how does this apply? When i was trying to work with huge amp mosfets, it was much harder to find ones that triggered at such low voltages, the low voltage ones , were leetel teeney parts.
The Mosfet is the transister type they use in protection and switching stuff for this stuff.

I'm glad I don't know a transister from a resistor from a mosfet from a diode from a capacitor. I would likely kill myself trying to learn. I was watching a TV repairman doing something in the back of the TV, and I was reaching towards something to ask what it did. He shoved me back and yelled something about getting electrocuted.

That was pretty much the end of my budding interest into the field of "complex" electronics.
 

VidPro

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LuxLuthor said:
He shoved me back and yelled something about getting electrocuted.

That was pretty much the end of my budding interest into the field of "complex" electronics.

getting electrocuted is the fun part, adds to the excitement. dont take anything I SAY about electronics as totally true, i learned only by the seat of my pants, often get the exact wording wrong, and didnt go to school for it. i just have been working with this stuff for a while, and trying to do stuff, that is not done the way i would want, or to do it cheaper.
there are real experts on this board.

and most modern CRT televisions discharge the thing that can kill you after a day or so, unless you are working on them with them plugged in :)
 
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