Batteries - please help!

[dervin1182]

Hey everyone, first time posting. I would love some help with batteries if someone is willing! I have a 2017 R7 w/ a Volvo 380. I’ve been getting low voltage warnings. I determined that one of my batteries was bad (failed load test). Both batteries were identical starter batteries. I want to make my house battery a deep cycle. I removed both batteries. Then I needed to figure out which was the starter battery - I traced the terminal to the bottom of the engine and located the starter. This was battery #1. I then hooked up a battery to #1 and turned my switch “on”. I was assuming that my radio wouldn’t work as I thought that battery was only for starting. But everything worked (radio, screens, head, lights, etc).

I then moved that battery to number 2. Same thing, everything worked. What am I missing? Isn’t the starter battery supposed to be isolated? I do have an ACR and a switch that is on/off/combine. I’m lost!

[jhnmdahl]

What does your switch look like? Some connect the house battery to house circuits and the starter battery to the starter circuit (or combined for an emergency start), while others let you choose battery one, battery two, or both combined.

If there's a model number on the switch, like 9000E or 6011E, that might be enough to help too.

[dervin1182]

The switch is “on/off/ or combine”. There isn’t a 1 or 2

[AsLan7]

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So glad you found us, d1182….

You are connecting those correctly.

Each side can power everything.

Use the number 1 for starting and running. Once anchored, switch to the deep cycle, for extended no engine operation.

And welcome aboard mate.

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[dervin1182]

Thank you AsLan7! Should I assume the ACR/switch will automatically switch to #2 at anchor? I can’t select battery 1 or 2. It’s just “on” or “combine”

[AsLan7]

Thank you AsLan7! Should I assume the ACR/switch will automatically switch to #2 at anchor? I can’t select battery 1 or 2. It’s just “on” or “combine”

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The ACR will allow the alternator to “top off” the first battery and when it is fully charged, the ACR will close and charge the second battery. While anchored, leave it "ON" (if there is a physical ACR switch). The ACR will isolate the starting battery from the drain of the house battery allowing you to have a fully charged starting battery. When your are done anchoring and cruising back in, the ACR will be open to charge the starting battery first from the alternator. When it has fully charged the ACR will close and charge the house battery.

When you get home, if you connect the charger to the house battery, it will charge the house battery first and when it is charged the ACR will close and charge the starting battery. The ACR works in both directions in the "ON" position.

The only time you should "Combine" the batteries is if your starting battery has died and that should only be done momentarily to start the engine and then it should be placed back into the "ON" position after the engine is running. If you place the switch in "OFF" you have disconnected the batteries from the boat, the ACR and each other. Btw, you should never switch a battery selector to OFF with the engine running as good practice not to damage the alternator.

[dervin1182]

Awesome explanation, thank you! My only other concern was to be sure the boat is wired properly (everything looks factory). With only 1 battery connected in the boat, everything was working. Shouldn’t electronics not work if only the starting battery was connected and shouldn’t the starter not work if only the house battery is connected? Sorry - I’m definitely not new to boating but this setup is way different than my last 1998 Mariah!

[jhnmdahl]

Here's an older thread that talks about the difference between different battery switches, how an ACR works, and the different ways an on/off/combine switch can be wired up and function: https://www.cobaltchat.com/viewtopic.php?t=414