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Help with Battery Cable and Class-T Fuse Sizing

Hello kgol, thanks for your reply. Because of the Electodacus SBMS0 battery management system rules, nothing can be installed between the positive battery terminal and the two shunts, therefore the T fuse would need to connected before or after those shunts and before the Lynx, making me question if it could just be bolted directly to the existing aluminum bar.
 
Thanks kgol for your quick response.

The reason I mentioned the placement of the T fuse in my system where I did is due to the use of the Electrodacus SBMS0 batter management system. The setup for this SBMS0 requires those two shunts on the positive feed from the battery bank and the rule is nothing can be installed between the positive battery terminal and those shunts. I'm thinking the T Fuse will need to be placed after those two positive shunts before or after the battery cutoff switch before the Lynx. I was wondering if anyone identifies a problem with bolting the fuse between the existing doubled up 1” x 3.5” x .25” (now .5” thick) aluminum bar?

Thanks, Greg
 
Hello kgol, thanks for your reply. Because of the Electodacus SBMS0 battery management system rules, nothing can be installed between the positive battery terminal and the two shunts, therefore the T fuse would need to connected before or after those shunts and before the Lynx, making me question if it could just be bolted directly to the existing aluminum bar.
If you install the main fuse at the battery and the shunt after the main fuse, then the Electrodacus BMS may indeed be damaged if the main fuse blows due to high common mode voltages on the shunt. Ensuring that the shunt always stays connected to the battery results in the shunt common mode voltage staying within range as it is the battery voltage. However, putting the shunt at the Lynx kind of defeats the purpose of the main shunt as the positive cable from the battery to the fuse remains unprotected (see explanation in my previous post).

That said, the BMS dying when the main fuse blows does not appear a safety problem to me as the battery will be disconnected anyway (main fuse blown, so no connection to anything anymore). Of course, always a bit sad when the magic smoke leaves a nice piece of electronics.

I don't think a dead BMS presents a large issue because the main fuse blowing is (or at least should be!) a very rare event. Most issues should get caught by the fuses downstream (the fuses in the Lynx in your case). For this reason, the fuses downstream should trip earlier than the main fuse. The main fuse is basically there to protect for shorts between the Lynx and the battery and for the rarely-happens-in-practice corner case that a fuse downstream fails to interrupt. It is very, very rare that the main fuse blows, and if it blows, then you should be very happy, because you averted a far, far worse event than loosing 200$ in a class-t fuse and a BMS.

TLDR: Put the main fuse close to the battery. If it pops then you loose the BMS, but you probably averted far more damage (fire etc.). For the inverter fuses in the Lynx, choose a lower current rating and/or 'faster' fuse such that an inverter overload does not cause the main fuse to pop.
 
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