Fan or heater


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johnallinson

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Feb 16, 2020
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16
Is there a reason BMS use things that heat to use the excess power in cells that are over voltage limits? Or would it not make more sense to run a fan from the cell to cool the batteries in the case of over voltage. Or us it just mechanical things have a higher chance of failure than passive components?
 

daromer

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Oct 8, 2016
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Why do you want to cool the cells when balancing? Generally you are in end of charge and they shouldn't be that warm.
You use passive dissipating because its simple and just works. You can potentially redirect the energy somewhere else but it cost money and most of the time the energy wasted is very low.

And if you have big issues with keeping balance its better to look into and sort the battery bank from the start. Its more cost effective.
 

ajw22

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Nov 16, 2018
Messages
715
I'd say space, durability, and cost. A typical 12cm PC case fan uses about 2Watts and costs $5 for a quality one, and still die after a couple of years. A dumb resistor can waste the same 2W in a much smaller package, last forever and cost just pennies.
 

daromer

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Oct 8, 2016
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Community? Its not this community that have chosed that. its the whole industry. Doesnt matter if its the home user or tesla or someone else :) Easiest way to balance is to dissipate into heat.

you can as said use the energy to many things but the energy is very little and converting it generally just cost more than it give.
 

Geek

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Aug 15, 2017
Messages
920
johnallinson said:
Is there a reason BMS use things that heat to use the excess power in cells that are over voltage limits? Or would it not make more sense to run a fan from the cell to cool the batteries in the case of over voltage. Or us it just mechanical things have a higher chance of failure than passive components?

If you over-charge a lithium chemistry battery, it will explode. They cannot dissipate excess charge as heat.
 
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