IP22 with three outputs, smart shunts, and battery selector switch

daynardi
Sat, 11 Apr 2026 18:43:36 +0000
DIY

I’m considering adding a three output IP22 charger to my boat. I’d only be using two of the three outputs.

I have two identical lead-acid batteries. Plan is to connect one output of the charger to each battery, with a smart shunt on each battery.

The two batteries are connected to the load by an “off - 1 - 2 - both” switch. When the switch is in the off, 1, or 2 position, the two batteries are isolated from each other. They would be charged independently through their respective outputs from the charger. When the switch is set to “both” the batteries are combined and the charger outputs would be acting in parallel.

I have two questions:

When the batteries are isolated, the smart shunt on each battery will work with its respective channel on the charger, presumably as advertised. When the batteries are combined, will the two smart shuts play together well or will the charger be confused by redundant signals describing the same circuit?

What is the maximum output of the 3 channel charger? I assume that the 15 amp capacity of the IP22 is allocated between the ouputs based on relative demand. The current on any channel could vary between 0 and 15 amps but the combined total would never exceed 15 amps. Is this correct?

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