Turning a 2 battery system to 4

Knot Waiting · Feb 18, 2013

I am installing a significant stereo upgrade this spring and would like to add more batteries to handle the load increase. Currently I have two batteries hooked to a single isolator (1/2/all/off). Any suggestions as to the best way to add two more to the system? I'd like to maybe have three as the house bank and then have a starting battery separated by an automatic charging relay. Any ieas from you electrical gurus are appreciated. Thanks!

Don S · Feb 18, 2013

Re: Turning a 2 battery system to 4

Just hook 3 batteries together in parallel for your house bank. Then it's basically one big 12v battery.
The isolator will work the same.

Knot Waiting · Feb 18, 2013

Re: Turning a 2 battery system to 4

Oh, well that's pretty easy then. Thanks Don.

You or anyone else have experience with those automatic charging relays? Are they worth it or would it be unnecessary with an isolator set up as described above?

trendsetter240 · Feb 18, 2013

Re: Turning a 2 battery system to 4

You could go the way Don suggested which would work to add capacity. Another option would be to replace the existing house batteries with much larger capacity batteries. Typically the 6v large capacity batteries provide the best amp / hour rate for the weight and cost. Wiring two 6v batteries in series as your house bank and keeping your existing switch setup would give you a nice boost in capacity.

ACRs work great and would basically be the replacement for your battery switch. I personally don't use them because they cost more and really only provide the benefit of not having to pay attention to where your battery switch is. If you can remember to switch the battery to the house bank after you start the motor you don't need an ACR.

Knot Waiting · Feb 18, 2013

Re: Turning a 2 battery system to 4

I think that's why I'm interested in the ACR. My isolator is currently located under the electric engine hatch (factory install) so to switch it I need to run the hatch up and down... slow, wear and tear, power usage, etc. So you think I could swap the swich and install an ACR instead?

Don S · Feb 18, 2013

Re: Turning a 2 battery system to 4

You can use the isolator or the charge relay, nothing to change with your system except to add some battery cables and batteries.
With the charge relay, you will need the charge relay, and a different battery switch, plus some rewiring to separate the house and engine systems. Not a big deal really, just more work and expense.
One disadvantage of the isolator is the fact that it cuts down the full charge of the battery by almost a volt, unless you add another diode into your sensing wire ( I think, haven't done it in 10 years) in order to make the alternator think it's putting out more voltage.

trendsetter240 · Feb 18, 2013

Re: Turning a 2 battery system to 4

Yep, you could switch to an ACR. The blue seas acr seems to be the most popular. There has been a ton of threads on how to setup an ACR on iboats. Just do a search and you will find everything you need. Also if you buy one it should come with some documentation for setup.

Don S · Feb 18, 2013

Re: Turning a 2 battery system to 4

Knot Waiting said:
I think that's why I'm interested in the ACR. My isolator is currently located under the electric engine hatch (factory install) so to switch it I need to run the hatch up and down... slow, wear and tear, power usage, etc. So you think I could swap the swich and install an ACR instead?

I must be missing something here, you don't switch an isolator. It's hard wired.

Here is a drawing showing your switch, the isolator, and all 4 batteries.

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Knot Waiting · Feb 18, 2013

Re: Turning a 2 battery system to 4

I don't think you're missing anything Don, I think I mis-applied the word isolator. What I was referencing was the battery switch.

I think I'd like to wire the system like you initially suggested (three in parallel and one independent for starting) but use an ACR so that the charging/separating process was automatic. That's what the BlueSea system TrendSetter mentioned does correct?

Don S · Feb 18, 2013

Re: Turning a 2 battery system to 4

Knot Waiting said:
I don't think you're missing anything Don, I think I mis-applied the word isolator. What I was referencing was the battery switch.

I think I'd like to wire the system like you initially suggested (three in parallel and one independent for starting) but use an ACR so that the charging/separating process was automatic. That's what the BlueSea system TrendSetter mentioned does correct?

I have a wiring diagram I did for another member with the ACR, give me a bit to find it and I'll post it. They are easy to install and wire in.

Auger01 · Feb 18, 2013

Re: Turning a 2 battery system to 4

I'm just guessing here, but I think the op is calling a battery switch an "isolator". That may be what is causing the confusion.

Disregard, you guys figured it out while I was typing.

Knot Waiting · Feb 18, 2013

Re: Turning a 2 battery system to 4

That'd be great if you could post the diagram Don, thanks!

Auger, yep, that's exactly what happened. I think in trying to figure out this electrical project a few wires got crossed in my head, lol.

Don S · Feb 18, 2013

Re: Turning a 2 battery system to 4

Ok, here is what your 4 battery system would look like with the Bluesea Add a Battery acr installed.

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Knot Waiting · Feb 18, 2013

Re: Turning a 2 battery system to 4

Wow... That... is... awesome Don! I'm printing that off and taping it to the hatch while I do this. I sure hope they pay you something for all your advice, I gladly buy from iboats in appreciation. Thank you all again, I'll check back in with the finished project.

Don S · Feb 18, 2013

Re: Turning a 2 battery system to 4

You do have to make sure all the wire sizes and fuses sizes are correct. The instructions in the ACR will explain what you need.
You can get the instructions in the link below.

http://bluesea.com/products/7650/Add-A-Battery - 120A

Turning a 2 battery system to 4

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