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What is the maximum short time (1 minute or 1 second) current of the BMV-702 500A shunt? Can the shunt handle a higher cranking current for a short period of time? I'd like to monitor the charge and discharge of my AUX battery, but it is connected to the starter battery for emergency cranking power. This means that there might be a short high current flow (battery CCA 950A) while cracking the engine. Can the shunt handle that or will it burn?
The short answer is that a typical shunt resistor like this could carry about 959A for a two second crank every minute.
It's unlikely that the 950A cranking current will be sustained for the whole 2 seconds, probably crank for less time and also only peak current at the top of the compression stroke.
Long Answer:
Crank for 2 seconds in one minute √(2/60) = 0.181
2/3 continuous power rating for 500A shunt = 0.667(500/0.05)=16.675W
Pulse power = 16.675/0.181 = 92.1W
Pulse current = √(92.1/0.0001) = 959.7A
I would not be too concerned.
Our 500A rated Victron SmartShunt has survived the starting current of our Canter 3.9l TD RV engine often multiple times daily for a few hundred (thousand?) starts.
Maximum peak draw measured is 740A but I am guessing for only a few milliseconds.
