Battery isolator question

[Joffa]

Hi all, looking for some help. Have a 2009 280 Sundancer with twin 4.3 mpi. There are 2 battery isolators which have 3 positions off, 1 & 2. Should the 1 position on each only be used for running house battery’s for fridge, lights etc when overnighting engines off etc? I’m running 2 house battery’s and 2 crank batterys….

 

[Jimmy Buoy]

You may be confusing "isolators" with "battery selector switches". Isolators work like one way valves, allowing current to flow one bank of batteries to another when a charging current is present. If no charging current is present, current will NOT flow from the battery bank to another.

From your description, you have 3 battery banks (one starter battery for port, one for stb, and a pair for the house). There should be 3 selector switches - one for each bank labeled appropriately.

It may be that your house has no switch and you simply turn it's 12vt breaker on or off at the panel.

If the two battery switches you have are as I've described, I'd put the stb engine to battery bank #1 and the port to battery bank #2. If either one is down in power and cannot start the engine, start the opposing engine, then switch the low battery switch to the good battery (on the running engine) and start the remaining engine. Then switch it back to the low battery so it will charge while the engine is running. If the battery is so low and in poor condition that the engine will not idle and dies, switch it back to the good battery to get back to port and plan on charging the problem battery then load test it for strength. It's probably beyond saving if this scenario occurs.

Not sure if you'd be able to utilize your house batteries for starting should BOTH starter batteries fail at the same time, but that's why it's good to periodically load test all your batteries.