Dual Battery Question

Dennis T.

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I have two batteries and the switch on my '14 24sslx. The original owner always kept it off when not in use and on All when in use to make sure both were getting recharged when in use. What is the best way to use the switch? I get his theory but it seems like it works against the idea of having one in reserve if needed. I thought of using one at a time and alternating every other outing but wanted to check in with the experts here before I made the change. DT.
 
I would say that is the correct way, while underway. The key is that if you are stopped and at the sandbar or rafted up, switch to only battery one or battery two. That way the other is still charged. Once started, combine them again to recharge.
 
+1 what Derrick said above. That is how we use our dual battery set up.
 
I've always just rotated each battery with each use. One day battery 1 the next battery 2. My charger has LEDs on the top so I can see how charged each battery is. It's probably not super accurate but enough to give you an idea. My goal is to use one battery all day with occasional stereo stops and always have a fully charged battery as a back-up. I've never had an issue and did the same when I had a SW fishing boat and went as far as a 100 miles out. Four batteries on the boat and rotated two at a time.
 
+2 on Derricks comments, that’s the way I do it.
 
So . . . when installing more than one battery - I always put in an ACR (Blue Sea) with a simple on-off switch. You turn the batteries on when you head out, and off when you get home. The ACR automatically combines the batteries when a charge current is present - and isolates them when there is none. If you stop during the day - your house and starting batteries are automatically maintained separately. If, for some reason, you get a weak battery, the ACR will allow you to combine them to allow you to start the motor.

https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A
 
My mechanic that installed when I bought it, said to leave it in the 1 position when in use and it would charge both batteries. If you let that battery run down after running the accessories, then switch to 2. Crank it up, and switch back to one and charge both again. It most likely depends on how they were connected.
 
Our dealer told us to do exactly like Derrick said. Both when underway, off when not in use, and one or the other when coving out, listening to the stereo, etc.
 
Don't switch with the motor running. The alternator will have nowhere to send the voltage and it can damage itself.
 
Folsom Dan, that ACR is a nice set-up for sure. That said, I leave my dual battery switch on "all" all the time. As responsible as it would be to change the setting depending on if I was running verses camped out at the sandbar, I think I'd quickly forget! In nearly 30 years of owning a boat, I've never run a battery down at the sandbar, let alone two of them. However, I have frequently walked into a room and had no clue what I was after...
 
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