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Hate to be that guy - but have a battery question.

The R5 we are buying came with a factory ACR. The current owner replaced the port battery last year but not the starboard. The new Port battery is a Interstate 24M XHD so just a starting battery.

I want to replace the starboard as its 7 years old. Since the house and engine loads are separated via the ACR would it make sense to buy an AGM and run an AGM for the house load and one Starting battery or just match the 24M XHD for both batteries?

Curious what works for others, look forward to the input.

The ACR determines which battery is charged or discharged based on each battery's charge level. It's designed to isolate the batteries when discharging so you don't run boat batteries down with accessories when the engine is off and not charging. Problem is you can't really designate one battery or the other as a house or starting battery. You would need a separate ACR for the house batteries if you want them separated like that. You usually see multiple ACRs on larger boats with multiple starting and multiple house batteries. I am not an expert on this, but this is what I learned when researching how the ACR works on my R5 - I have matched batteries.
The ACR in your boat is made by BlueSea - might want to read through their documentation to understand it better than my layman's explanation - those switches are quite sophisticated.

It's really up to you how much you want to spend on a battery or how often to replace it. I've kept mine for maybe 8 years before replacing, but stagger replacement between two batteries so I get a new one every four years. I can combine batteries with the battery switch to start if it's ever needed, but I've haven't had to use this feature yet.

As for the battery itself, I've been buying the Interstate Marine/RV group 24 or group 27 batteries from Costco due to the significant price difference between them and an AGM battery.

I saw your question on the Facebook site. You can have any type of batteries since both Flooded and AGM are both lead acid batteries and have similar charge profiles. No charger you will ever use, including the boats alternator, would be able to differentiate between the two.

If it was my "new to me" boat, I would just buy two new AGM batteries and be done with it. AGM have lower self discharge so if the boat sits awhile between starting, the batteries won't discharge as much. I bought the Duracell group size 31 AGM from Sam's Club. I also buy Odyssey batteries as well. My next set will likely just be Odyssey. They are expensive but worth it.

The way an ACR works is that it looks at the voltage of each battery. When one of the batteries gets over a certain voltage(when engine is on or a charger is present), it uses a relay and connects the two batteries. It has a voltage cutout that disconnects them once the engine or charger turns off. It has no way to determine the state of charge of the battery. If one battery is below a certain voltage, it won't let the connect in case something is very wrong with that deeply discharged battery.

When I added my charger, I put the output of the charger on the battery side and the ACR on the engine side of the disconnect switch. That way, when the switch is off, using a dual output charger did not engage the ACR so that each battery is isolated during charging.

NautiGirl wrote: Tue May 14, 2024 8:49 amThe new Port battery is a Interstate 24M XHD so just a starting battery.

You probably already know this but the port battery is the battery that starts your engine. Since it is new, you can just buy a new AGM battery for the starboard side.

Well, when it comes to batteries, questions are totally cool. So, here's the deal: with your R5 rocking that factory ACR setup and you're eyeing a replacement for the starboard battery, think about snagging an AGM for the house load and sticking with the 24M XHD for starting. It keeps things straightforward.

Now, if you're up for exploring new options, consider checking out lithium-ion batteries. They're pretty advanced, with longer lifespan and lighter weight. You can find more info about them here:https://www.pknergy.com/lithium-ion-battery-pack/. Might be worth considering if you're still searching for the right fit