Battery Isolator

[LuckyPenny]

I know I read it somewhere here before, but for the life of me I can't find the original artical. so here it is again.

I want to install a battery Isolator, however, my set up is somewhat different than most of the references I have found. I have three batteries and one '1 both 2 off' switch. Two of the batteries arewired together for housekeeping, and the third is devoted to starting. I want to put the isolator on the house batteries to equalize the charge (they are the same type) I do not want to mess with my starting battery.

What I do is start up and run for about 20-30 minutes on the starting battery, then switch over to housekeeping. and run the rest of the day on them.
I want to use the isloator to balance the charge between them.

Can someone direct me to a site or explain in simple terms how to wire this up?

 

[Don S]

Re: Battery Isolator

All you have to do is hook the 2 house batteries in parallel. Pos to Pos, Neg to Neg and you basically have a single battery. No reason in the world to have them isolated from one another.
What you are trying to do is make yourself a house battery bank of 2 or more 12 volt batteries, not a bunch of batteries that can be used seperatly as house batteries only.
Many use a "Battery Combiner" or "ACR" or "Automatic Charge Relay" or what ever different companies call them. They are voltage sensitive relay that connects your batteries together to charge all of them once your start battery is charged up to about 13.5 Volts.

Blue Sea has a lot of info on them.
http://bluesea.com/

Here is one of their products that basically does exactly what you are doing all buy itself. Only better without you doing anything.

http://bluesea.com/products/7650

Here is some info comparing the Isolators with the Charge relays.

http://bluesea.com/viewresource/58

EDIT: Change wrong word to correct word. Parallel instead of Series.

 

[johnbo]

Re: Battery Isolator

I would only add two comments. First, what Don probably meant to say was "parallel" instead of "series". His wiring description is for "parallel".

You stated that both of the house batteries were identical. It is quite important that they really are identical, and have similar lifetimes, etc. They will also need to be replaced as a set. The issue is that the batteries will tend to equalize each other.

If one has a little more voltage, the other will 'charge' from it. Obviously, these actions are lossy, so the batteries will sit there and trade current back and forth, turning the stored energy into heat. Not much, but heat, which means that the battery is discharging, without providing any useful power to the boat.

With identical fresh batteries this really not an issue (until they start to fail). Combining two batteries with different 'life histories' can cause some problems.

The advantage of the isolators is that the diodes in them will keep the batteries from feeding off of each other. So, if you lose a cell in one battery, the other will still be working to power your boat, not trying to charge the dead cell in the bad battery.

I hope that helps.

johnbo

 

[bjcsc]

Re: Battery Isolator

edit

Combiner is the way to go. You can't beat this deal with a stick...

 

[Don S]

Re: Battery Isolator

Great catch guys.
Believe it or not, I really do know the difference. :%

I did go up an edit the original post so it doesn't say series any longer.

 

[bruceb58]

Re: Battery Isolator

The battery isolator method is the "old school" way. Combiners or ACRs are the best way now.

 

[Dunaruna]

Re: Battery Isolator

[colour=blue]Don, that's what we old folks call a 'brain fart'. :%

 

[Don S]

Re: Battery Isolator

[colour=blue]Don, that's what we old folks call a 'brain fart'. :%

Works for me