Xantrex 20+ charger install issue

[jleger98]

Ok, I'm bringin this one back from the dead.

Maybe this is out there on another thread somewhere, but any of you guys have a diagram of how to set up two batteries, one isolator, and a xantrex charger? I have the xantrex 20+ charger, and it seems to allow charging to more than one battery. Should I have this hooked up to my cranking battery as well? And in that case, am I just bypassing the isolator??

I have an idea, but don't want to screw anything up.

[TigeDuner]

I used the perko switch without the isolator. I have two batteries for sound connected to the xantrex 20 on one bank and the starting battery on another bank on the xantrex. Pretty simple. Switch the perko to the sound system batteries when parked and on both when running.
Good luck.

[jleger98]

The whole idea of the isolator is that I wouldn't have to switch anything. right??

[TigeDuner]

I believe if you read the post about isolators you will find that the isolator decides which battery to charge. When you are anchored or beached, you will want to only draw power from your sound system batteries. The only way to draw from the sound batteries is with a battery switch. The isolator distributes the charge, the switch decides which batteries get used. I see the isolator as redundant with a battery switch, but it does eliminate you switching the switch to direst the charge to the batteries. I guess I don't want to mess with the isolator so I just switch the switch then plug in at camp to complete the charge... Confused yet???

[jleger98]

Confused? yes.

So here is what I am thinking. I'm sure there is a better way.

[lee]

The only way to draw from the sound batteries is with a battery switch. The isolator distributes the charge, the switch decides which batteries get used.

An isolator also dictates which battery is a starting battery and which one is an accessory battery thus doing the same as a switch but without the owner having to switch anything.

[TigeDuner]

Lee is right, like your sketch. I am so use to the switch that I forgot that you could simply substitute the isolator for the switch and be done. My mistake.

[chpthril]

J, you diagram looks simple enough. This will allow you to charge both banks (starting and stereo banks) at home or in slip without messing with the Perko switch.

To add to Lee, the Isolator works as a "1 way electrical valve" It's a Diode. It will allow the alt to charge both banks while the engine is running, but will not allow your accessories to draw power from the starting battery when you are anchored/beached.

With an Isolator, the Perko is really not need, but it's nice to have because it will allow you to start the engine off the acc battery(s) if the starting battery ever fails.

[jleger98]

With an Isolator, the Perko is really not need, but it's nice to have because it will allow you to start the engine off the acc battery(s) if the starting battery ever fails.

I guess if the starter batt ever fails. I can just do some quick rewiring to get it to start.

So will the isolator choose to charge the cranking batt first? or will it charge both evenly?

[chpthril]

I guess if the starter batt ever fails. I can just do some quick rewiring to get it to start.

So will the isolator choose to charge the cranking batt first? or will it charge both evenly?

I wasn't sure so I googled. This is from Cole Hersee Resource Center

How does a Battery Isolator work?
Simple. It's an electronic sealed unit that contains two diodes.

Diodes, if you remember, permit current to flow in one direction only. Power supplied to the middle stud of the Battery Isolator flows to each of the other studs. Current cannot flow back from one of the batteries to the other battery. Charging current flows preferentially into the battery with the lowest charge (because of the higher potential difference).

Because they're solid state, isolators have a long life. They're not susceptible to contaminants, vibration, or extremes in temperature

Why use a Battery Isolator?
So now you've got two batteries and one means of charging the batteries. If you connect them all together the batteries drain from the one with the higher charge into the one with the lower charge until they're equal. That's not too bad for a deep-cycle battery, but it's disaster for a starting battery, because you might have insufficient power to start the engine. You might also be drawing down too deeply on your starting battery, which will lead to premature failure.

The option is to create two independent circuits, each controlled by an On-Off switch (we've got lots of these at Cole Hersee!) or a battery selector switch. If you're a methodical person, this could be OK for you. You have to remember to charge up both batteries in due course. With a Battery Isolator, you can forget this problem.

[jleger98]

Wow, good find.

So if I read that correctly, if I sit at the beach and chill with the tunes for 6 hours and run my deep batt down, the isolator will try to charge that one over my starter battery?

[chpthril]

Wow, good find.

So if I read that correctly, if I sit at the beach and chill with the tunes for 6 hours and run my deep batt down, the isolator will try to charge that one over my starter battery?

Yes. When your ready to head home, your starting battery will be at full charge (because of the Iso) and will start the engine right away. Now that the Alt is putting out, the Iso will sense that the Deep(s) are low, and send all or most of the charge to them.

Remember, A good starting battery will hardly be phased by 1 or 2 cranking attemps so it will still have plenty of reserve even though the deeps are getting most of the attention.

[jleger98]

Yep. Thanks for the clarification CP. Once again, vast repository of actual useful information