battery isolator?

got a question about battery isolators. Reading past threads, it seems that most of the battery isolators automatically combine when the boat is running. That means my starter has both batteries to draw from, but that my stereo has both batteries to draw from as well.

I want to isolate my stereo battery from my main battery all the time, not just when the boat is off. will anything allow 1 alternator to charge 2 batteries, but keep them isolated?

Get a battery separator/combiner. Isolator's cause a drop in voltage. My company sells one from Sure Power. The part number is 1314. It separates the batteries and gives priority when charging to your starting battery so that you don't get left high and dry. They are also very affordable and don't cause a drop in voltage. They are about $50.

http://www.surepower.com/separator.html

How does that work compared to say a stinger isolating relay?

so that will combine the batteries when starting, but not during normal operation?

di
this might answer your questions, like brett said the separator is the way to go, info here also: http://www.ase-supply.com/Sure_Power_Isolators_kits_s/20.htm

I use the Hellroaring 95150B unit. Just put it on and forget it.

www.hellroaring.com

The system skier's choice started using for it's dual battery setup is great. They use a "perko" style switch along with a combiner. It gives you the most control over yrou batteries/charging.

dj ,, look for a Smart Combiner . It will only tie the batteries back together after the voltage reaches 13.5 or so . Meaning that it will leave the batteries seperated until it see the charge of the alternator , not during starting . We use the Yandina C100 on alot of the boats we put systems in and works great as long as the alternator is not more than 100 amps .

(Message edited by jrhurst on April 10, 2008)

Jeremy that is xactly what Adam's post does, btu includes the perko style swithc for even more flexibility. The sytem above is hands down the best way to run multiple batteries.

dj said: it seems that most of the battery isolators automatically combine when the boat is running

No, that is not what an "isolator" does. An isolator, in the strict term, is a couple of diodes that allows the alternator to send current to two different batteries while not allowing one to discharge the other.

The diode isolators are old technology and have all sorts of drawbacks, primarialy a major reduction in charge rate.

A "Combiner" is a more advanced device that works like an automatic battery switch. It is a little more intelligent than just connecting the battery when the engine is running, which you can do wiht a fairly inexpensive relay.

A combiner will monitor the voltage on two batteries and connect them together whenever the voltage on either one exceeds a certain set point, generally around 13.1 volts. Once connected the combiner will keep them connected until the voltage drops to a lower voltage, around 12.7 volts.

Such a system will connect the batteries whenever either one has a source of charging, which could be from the engine alternator or from a battery charger. It will only connect if the voltage is high enough for charging, which is NOT necessarialy the case of the engine running. A typical alternator will have very low output at idle, so the combiner may not activate until you clear the 5 MPH zone.

A combiner, alone, will allow you to keep two batteries charged and prevent your amps from draining your starting battery.

What a combiner will NOT do is allow you to use your second battery to help start the engine in the event your engine battery died. This is why many people also install the good old fashion battery switch (often referred to as a "Perko" switch). If you also install the battery switch just be sure to leave it in the "open" position, otherwise it defeats the purpose of the combiner.

Rod}

Rod, as long as the perko switch is 1, 2 or both the combiner will work proeprly.

Rod, good explanation. If you look at the link I posted about the sure power product and click on the printable brochure it gives you a better explanation than the original link. That product senses the batteries voltage at start and if the starting battery is low it will combine them to help with the start. There is also a couple of terminals that you can connect to a switch on your dash so you can manually combine them to aid in starting. The 1314 Sure Power is rated up to 100 amps, but a 200 amp version is also available.

sorry for beinga dunce, I should know this, but I have one more question,

lets say I use a combiner, and both batteries are chared so they are combined. If I have my stereo all on one battery, and the boat on another, and while jamming the stereo it draws a 60A current, will that current be drawn from only the stereo battery? or will it draw from both, but it doesnt matter because as soon as there is enough voltage drop the combiner will uncombine and then the stereo will draw from the stereo battery?

The issue i've been having is that when I jam the stereo, the boats 50A breaker on the engine will pop. I only have a perko switch a/b/all, that I typically keep on all. Im trying to figure out if an isolator/combiner would solve my problem, or if I just have a completly seperate problem and it just so happens when I jam the stereo.

Isolate your stereo from the rest of the boat.

DJ:

If you are popping the main breaker then you obviously have your amps wired to the main power distribution for the boat. This is a bad idea as the wiring harness was never intended to run that kind of current.

You should have a dedicated circuit to the amps. This circuit should include a fuse or circuit breaker located as close as possible to the battery. Run heavy gauge wire; 4 AWG for a single amp if it is close to the battery, 2 AWG for multiple amps. You may need a distribution block next to the amps to terminate the 2AWG into 4 AWG lines that the amps can handle.

With a battery combiner the stereo battery will be disconnected when the engine is off. If you are drawing significant current, such as the blower, ballast pumps, etc. the combiner will probably not kick in until you are out of the 5 MPH zone. If, while you are running, the load becomes too much for the alternator and the voltage drops too far (12.7 volts) the combiner will open and isolate the two batteries. You stereo battery may go dead but your starting battery should always be safe.

Rod

Sam wrote: "Rod, as long as the perko switch is 1, 2 or both the combiner will work proeprly."


If you have the "Perko" switch on "BOTH" the isolator will be defeated. Run the stereo with the engine off and you will have two dead batteries.

If you have a three position battery switch, leave it on the setting that connects the engine to the battery that isn't connected to your amps.


Rod

I have had great luck with this product
http://bluesea.com/productline/overview/387
Simple clean instalation. Hooks up in about 10 min's and works great.

You take a lead from your starting battery and connect it to the A side of the ACR. Then you take another leed and you connect it to your stereo batterys and connect it to the B side of the ACR. Hook up a ground and your done.

I have had it working in the family pontoon boat for a year now and it works great

^^^ That is the same product my buddy recommended that does electronics on yachts.

Its a simple easy to use item. This is how it works
your starting battery starts the boat independient of the stereo batterys. As soon as the starting battery hits a pre set voltage it transfers the charge over to the stereo batterys, I.E the overflow voltage from the start battery runs into the stereo battery's. It sepperates the batterys anytime the Draw or voltage is differant. Plain and simple battery combiner. No switches or buttins to push or turn just hook it up and forget about it

Just installed that in my boat Grant. Glad to see that it is working out for you. It also has a lead to hook up a LED to see when the batt's are combinded. I hope to see if it all works this weekend. I'm a mechanical guy, I'm not good with electrons, but it was a simple hookup.

Yes there are 3 connections at the bottom on the ACR.
1 is a ground. Hook this up
2.is a for dash mounted LED to show you the batterys are combined (this is a optional hook up)
3.is a key'd connection. Dont hook this up.

Customer service at Blue Sea is great. If you have any questions call them they will help you out no problem, Also if you have any other questions they have online wire diagrams to show you were the wires go. "Easy Peezy Lemmon Squeezy"

I guess my install is just f-ed up. Im just going to rip it all out and start again. got some more amps to install anyways

I think I figured out my 50A breaker poping issue. and I think its simply the fact that I upgraded my alternator, upgraded my stereo, but never upgraded the wiring from the alt. Its still the 10 guage wire running to the breaker, then to the starter? or does it go to the battery from there? Not sure yet.

reading through the archives I see that I could just run a big wire 0/2 from the alt to my battery bank in addition to the 10G wire that runs through the breaker. But wont that bypass the a/b switch? since I would have2 paths from the alt to the battery?

should I replace the 10G with 0 gauge and upgrade the breaker to a 100A?