Dual Battery Charging Question

[Scoop]

I stand by my comment. All that info and the original question still wasn't answered. "My question is why does it appear as though both batteries seem to take the charge when I'm only charging one battery? You stated previously on Dec. 14- "The isolator keeps the batteries separate when voltage drops to 12.9v or below. Conversely, when voltage gets to 13.4v (whether when the vehicle is running or you are charging the batteries), the isolator connects the two batteries (in parallel) and begins charging them simultaneously." and clearly used the term "connects" which implies it was disconnected so you really haven't made a point other than to confirm the accuracy of my comment.

You can't just charge one if the isolator is doing what it's supposed to do.

If you understood the purpose of the isolator, you wouldn't be asking this question again (which was most certainly answered).

 

[Admin]

 

[bumperm]

I can understand why some folks get confused with all this electrical stuff with electrons running around and blowing fuses (though Scoop is right again on his previous post). The U.S. Navy sent me, as a young lad, to Electronics Technician Class-A school (at Treasure Island, S.F. CA) back in 63 - 64. That was 48 weeks of nothing but intense electronics training.

And I still sometimes get my wires crossed. Just ask my wife!

 

[Hondasxs]

You can't just charge one if the isolator is doing what it's supposed to do.

Meaning.. (just for clarification)
- Because it will charge BOTH?
or
- because you have to charge BOTH?

 

[bumperm]

If you are using the True isolator, when you charge either battery by either running the engine or by using an exterior charger, the battery/s will be charged accordingly, (this assumes the True is installed according to their directions with one of the two large 5/16" terminals on the True going to each battery positive.

When the engine is running, the electrical system will charge the main battery. As that battery voltage increases above 13.3 volts (or so) the True will connect the two battery positive terminals, indicated by the blue light coming on steady, to charge the aux battery. When the engine is shut down, the blue light will stay on until the main battery falls below 13.3 (or if the aux battery is above 13.3, until it too falls below that approx. voltage) - note that the at rest battery voltage of a fully charged Pb battery is about 12.9 volts, but it will be above that level for a good while if there's no load and it just came off charge.

If a shore power charger is connected to the aux battery, it and the True isolator, will behave in the same manner in the opposite direction - i.e. as the aux bat is charged above 13.3 the True will start charging the main battery. All of this is normal.

True suggests connecting the shore power charger to the aux battery, as this battery is often drawn down by winching and other electrical demands with the engine is off.

The True will allow one battery to assist the other battery, but only so long as the "high" battery remains above 12.9 volts. So if your are winching away with the aux battery and engine off, if you manage to pull yourself free, the main battery will have the energy necessary to get you on your way.

 

[Scoop]

Meaning.. (just for clarification)
- Because it will charge BOTH?
or
- because you have to charge BOTH?

Yes. 🤣

Clearly, if you charge until the blue light shines then disconnect, you've only charged one. But when the two are linked ... you're essentially charging both (even if the one, which is @ 13.4v, is passing along to the other).

But you already know that! 😏

 

[hopeicanaffordthis]

Hey,

i also have the true- am and a battery tender wired up to my main battery. it just started getting cold out so i thought i'd test the battery tender out. I had it on for about three hours and came back to my isolator being hard lit blue. is this correct?

Actually, once charged the light on isolator turns off. should be fully charged on both batteries, i assume?

 

[Scoop]

Actually, once charged the light on isolator turns off. should be fully charged on both batteries, i assume?

Per DFNA (the official retailer for True Amalgamated, who produces this isolator):

"When all voltage sources drop below 12.9 volts* (cut out threshold) the Smart Battery Isolator will disengage and the blue LED will go out."

I posted that earlier in this thread.