I am trying to seperate the battery system on my boat into a engine/house array. What is the best way to distribute charge to the various batteries. My local dealer says isolators, but I have researched and found you lose some voltage through them and dont get a complete charge to the batteries. I see blue seas sells and charging relay that supposedly doesnt drop the voltage. Or any other products I havent mentioned. I would apreciate input from someone who has done it, or is knowledgeable. Thanks

I run the Blue Sea Systems ACR (Automatic Charging Relays) in my rig. Each engine has one, which keeps the engine batteries isolated from the house batts, but when either engine batt is topped off, it sends the charge to the house.

When you use an isolator, you have to run your alt wire to it, then it gets split to each battery bank. With an ACR, you just put it between both batteries, no changing the alt wire around.

I'd venture to say that people who recommend isolators have no idea what an ACR is and stick with recommending old technology. They work fine, just not as effecient.

I use the Hellroaring isolation system-charging system. It completely isolates one battery, which I use for my stereo, amps and a few other power draws. Have had it in my boat for 2 years without any problems.

http://www.hellroaring.com/bic75150.php

Ok, I am going to use relays. Kind of confused on which way to set them up though. Would it be better to run the charging lead from the alt. to the starting batteries then put the relay in between the starting battery and the house array, or should it be the other way, alt. to house and relay to starting. Would be a lot easier to leave it the way it is now(alt. to starting batt. on each motor). Then I just have to transfer all the house leads over to the house batteries(now they are all on #1 starting batt).

Really won't make a difference for most use which way you go since your start battery circuit will always be isolated from your house circuit in either config, so you will always have a fully charged start battery, which is preference. The use of the ACR's don't have the voltage loss that are in isolators, so another factor for no 1 way better than another.

Usually the draw to start a motor will be replenished within a few minutes of run time, so the charging will go to your house bank there abouts, if the charging source goes to your start battery.

A boat started/ stopped often and run in short spurts may be better to have the start battery hit 1st, such as fishing boats to make sure the start batteries are topped off 1st. Boats ran for longer periods of time with fewer starting times, can have the house bank as priority since the starting battery will usually never be drawn down as much and not require a long replenish time.
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You need to be sure that the alt. sensing wire goes to the same battery as the alt output lead, if so equiped.

I'd just go the start battery as initial charge receiver and let the acr handle the house load for simplicity.

Does your alt lead go directly to a battery now, or to the starter solenoid?

An isolator (large diode) has a 0.7v drop and will not fully charge the battery(s) - this is countered by running the alternator voltage wire (if you have one) to the battery itself.

This causes the alternator to output a higher voltage and charge the battery as it should.

The problem is that is the alternator looking at only a single battery, and thus can overcharge the other battery in certain situations (if you have a battery going dead, etc). This is bad, and can be very bad.

Use the Blue Sea ACR and be done with it.

http://www.defender.com/product.jsp?path=-1|328|51495|299265&id=776743

I bought this. This seams to be better technology then an isolator

West Marine combiner. Engine battery goes to #1, house bank to #2. It combines the banks once the cranking battery is up, and separates them if they fall below a pre-set point. You can also turn it off by switching off the ground wire. All I needed was two short lengths of #4 wire from the hot posts of my battery switch, and a switched ground wire.

Go the Voltage Sensitive Relay (VSR) route.