Battery Isolator Installation Question

[minnmarker]

OK, I get your points.  Maybe I'm missing something about battery conditioning?  The SI-ACR circuit does not close (in the shore charging situation we're talking about) until the stereo battery reaches 13 volts for 2 minutes.  Would it still suck current off the starter battery?

In the case of charging underway, it has a lockout that prevents closing the circuit when the stereo battery is drained below 9.5 volts and the alternator is charging the starter battery.  I can see where it might draw current from the starter battery when the alternator is doing the charging and the stereo battery is above 9.5 volts.  Will that shorten the starter battery life?

[MLA]

Quote

until the stereo battery reaches 13 volts for 2 minutes

The charger will likely produce this voltage level out of the gate, rather then the ACR seeing the actual static battery voltage. Thats where the issue is. 

[shawndoggy]

25 minutes ago, minnmarker said:

OK, I get your points.  Maybe I'm missing something about battery conditioning?  The SI-ACR circuit does not close (in the shore charging situation we're talking about) until the stereo battery reaches 13 volts for 2 minutes.  Would it still suck current off the starter battery?

In the case of charging underway, it has a lockout that prevents closing the circuit when the stereo battery is drained below 9.5 volts and the alternator is charging the starter battery.  I can see where it might draw current from the starter battery when the alternator is doing the charging and the stereo battery is above 9.5 volts.  Will that shorten the starter battery life?

 

It's not the stereo battery that reaches 13v, it's just that the acr has to sense 13v of current.  Your acr is "dumb" in that sense -- it just senses that there's a charging current and closes the relay (assuming that the battery on the other side of the relay isn't below required voltage).  Your charger probably puts out around 14.5v the second you put it on the stereo battery, so that 2 minutes starts ticking as soon as the charger is hooked up.  so the relay will close long before the stereo battery is charged, and then yes, the starter battery and stereo battery become one big combined bank, and your single bank charger will try to charge it.

There's an easy "fix," as long as you only want to charge the stereo battery -- just pull the ground wire on the relay when on the charger (then the relay cannot close), or you could even rig a second relay to disconnect the ground wire to the ACR when the ignition is off.

 

Edited March 17, 2016 by shawndoggy

[MLA]

Or just use the proper battery switch?

[David]

9.5 volts??? Can you confirm that. Is that threshold adjustable? That's just way too low to be practical in any application. For rating purposes (Amp/Hours, etc.) 10.5 volts is considered empty for a 12 volt battery. And you should not be discharging below 12.0 volts on a consumer grade battery, which is considered a 50% charge level. Discharging below 50% will have a dramatic impact on the battery longevity and available cycles. If doing that with any repetition, you will notice a performance difference within the course of a single summer.

[David]

Btw, whether an ACR has an under-voltage lock-out or not, if it were to 'Close' with a battery showing 9.5 volts that would likely cause the voltage to sag on the sensing side and the ACR would immediately bounce 'Open' again. Which is why some people return to dock after a long stay at rest without getting any charge on their stereo bank.   

[shawndoggy]

1 minute ago, MLA said:

Or just use the proper battery switch?

hahaha see my first post in the thread where I said just buy the kit!

 

 

[MLA]

14 minutes ago, shawndoggy said:

hahaha see my first post in the thread where I said just buy the kit!

 

 

Another method rather then tying a relay to switch ignition, you can use an AC relay and the 87a terminal to open the ground circuit when the charger's AC cable is plugged in. 

[minnmarker]

3 hours ago, MLA said:

Another method rather then tying a relay to switch ignition, you can use an AC relay and the 87a terminal to open the ground circuit when the charger's AC cable is plugged in. 

Now that's the solution I can use!  I've had trouble before with "the kids" and battery switches.  The more fool-proof the better.  Plug it in and leave.  Thanks for the knowledge everyone and I hope the OP got what he needed as well.

http://www.functionaldevices.com/building-automation/display.php?model=RIBU1C