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paulmv avatar image
paulmv asked

two 12v starter batteries, one 24v aux bank wiring question

I have an Orion-TR Smart 12|24--15 isolated DC/DC charger that I want to use to charge a 24v bank of batteries for a trolling motor on a boat. The boat has 2 12v lead acid starter batteries and an isolation switch that allows one to choose between starter battery 1, 2, or both. The wiring diagram in the manual only shows a single starter battery. So my question is can I just hook the charger input to to one of the two charger batteries, which would be by far the simplest for me, or do I need to wire it in above the isolation switch? Thanks.

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Bob K avatar image Bob K commented ·
Does your isolation switch also determine whether the selected 12v starter battery receives a recharge current from your 12v alternator? For example, if your isolation switch is set to Battery 1, does Battery 2 receive current from the alternator? Or does the alternator only "see" Battery 1?
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Bob K answered ·

If you wire the DC charger to a battery, that battery -- and subsequently, the DC charger -- will only receive charging power when the switch is set to that battery. Alternator >> Switch >> Selected Battery >> DC Charger.


To get around that, a better option would be to wire the DC Charger into the alternator side of the switch (perhaps directly to the alternator + stud if there's room). That way, no matter which switch position you have selected, the DC Charger line will receive charging power from the switch-selected battery and the alternator.

If it's easier to wire to a battery, you'd just have to make sure that your switch has that battery selected in order to send power to the DC charger. You'd also have to make sure that your Engine Shutdown Detection or Input Voltage Lockout settings were correct so that you don't deplete the battery (that the DC charger is wired to) when that starter battery is not selected via the switch.

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paulmv answered ·

I don't know. But it's pretty old school, mechanical switch. So I think it's probably just a straight ahead connection. Thanks.

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paulmv answered ·

meaning. I think when battery one is selected battery two is completely disconnected from the circuit and vice versa. when I looked at back of switch, there are the two positive cables coming in from the two batteries, and one positive going out/in to the engine/alternator.

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