I am looking at putting a Victron Smart Shunt on my marine battery bank.
I am using AGM batteries and they are starting a Cummins 6CTA motor. The cold cranking amps on these motors is 1,250A. This is only momentary at the start.
What is the proper Smart Shunt Size that I need?
Personally I would use the 2000a shunt. Yes the 1000a shunt will probably work, but I’d sure hate to burn it up on an extended crank situation. For the extra $100 I’d personally not chance it
Alternatively, you could just run the starter ground back to the batteries directly. If the batteries are going to achieve a full charge while the engine is running, it really doesn’t matter if the starter is tied into the shunt. Once the charger has peaked the shunt will see this and reset the soc to 100% and only from there does it really matter for accuracy of soc that any draw is through the shunt until the next full charge
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