Sizing a smart shunt

DIY
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1

Installing a new smart shunt, I need to decide 500 or 1000A rating.

I have Epoch 12V 460Ah in parallel, 4/0 cables, and 250A class T fuses for each battery.

The fuses are sized such that the cables stay within their ampacity up to where the fuses will blow, at about 150% of rated current. We don’t have a lot of high-powered equipment, so the system is a bit oversized.

Is a 1000A shunt an unreasonable overkill? I assume you want keep the maximum system demand at less than 80% of rated current.

2

If you have no chargers or loads above 500A then use a 500A shunt. The 500A shunt will take short term currents higher than this but will not measure them.