Fuses for BMS sense/2a balance lines??

Discussion about pairing third-party batteries with OutBack equipment
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Sparkey
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Fuses for BMS sense/2a balance lines??

Post by Sparkey »

Any opinion on installing 2 amp fuses between the battery and the BMS that has 2 amp active balancer?? Have seen several videos of this being done and not being done to protect the surface mount input .01 ohm 1/16 amp resistors that act as 2.5 amp fuses.. It would seem to be a lot easier to change one of these external pico fuses then mess with on the board chip resistors..
chrisski
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Re: Fuses for BMS sense/2a balance lines??

Post by chrisski »

No fuses IMO.

In the 3 BMS I’ve installed with active balancing, all on 8s packs, I’ve always counted on the tiny BMS wires to melt out if shorted. I think the term is fragile link. Wires were just 20 AWG or 27 AWG.

Also not sure what that extra voltage drop from adding a fuse would do to the readings with the extremely small amount of current flowing.

I decided this after reviewing several threads at diysolarforum
Sparkey
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Re: Fuses for BMS sense/2a balance lines??

Post by Sparkey »

The JK BMS allows for user adjustment of the total resistance of the sense/balance wires I assume to allow a manual correction of the voltage drop where wire length or other resistive imbalance between the lines occurs.. Talked with Ausie Andy who has the off grid garage YouTube channel and he says he uses 5 amp fast blow fuses.. Since the .01 ohm 1/16 watt chip resistors are calculated to fry at 2.5 amps and they would be considered slow blow devices I figured that 2 or 2.5 amp fast blow would keep me from having to remove and solder these microscopic parts.. After checking price and availability at a couple of part houses I find that for the most part there is nothing in the proper range in stock or they are extremely pricy.. So for now I will just go without and hope this never happens to me.. If it does I will order the repair parts and most likely use a similar strategy of a resistor as a fuse since I can get a similar rated resistor for a couple pennies a piece.. Now if I only had a set of #00 crimpers, still trying to find my ham radio comrade who helped me crimp 30 of these things 5 years ago..
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