Automatic Charge Controller design issue - no battery voltage on B terminal

[dbsoundman]

Hi all, I have been wondering why my Blue Sea SI-ACR never combined the bus batteries with the house system when the bus was running (alternator on), and today I did some more reading and finally figured out my problem.

My plan all along was to charge at a max rate of 30 amps, and use my solar charge controller as the one and only charge regulator. Therefore, I connected my SI-ACR to the bus' batteries on the "A" terminal, then connected the "B" terminal to a manual selector switch so I can change between shore/solar and alternator charging sources. The output of that switch then goes into my solar charge controller.

For those of you that know the SI-ACR, you know that this won't work, because the SI-ACR will never see any voltage on it's "B" terminal, so it never "combines" the batteries.

That being said, I looked at DC-DC charge controllers and holy crap they are expensive! (At least the Sterling ones, I don't trust Renogy, nor do I trust the Amazon brand du jor.) So, is there some other simple device I can find that will simply pass voltage when it senses an input voltage that's alternator-level (>13 volts)? Or am I stuck with manual switching until I get a DC-DC charge controller?

[Rucker]

Originally Posted by dbsoundman

That being said, I looked at DC-DC charge controllers and holy crap they are expensive! (At least the Sterling ones, I don't trust Renogy, nor do I trust the Amazon brand du jor.) So, is there some other simple device I can find that will simply pass voltage when it senses an input voltage that's alternator-level (>13 volts)? Or am I stuck with manual switching until I get a DC-DC charge controller?

Just search Amazon for dual battery isolator. They might peak out at about 15 amps, and only work with lead acid batteries. I know of no cheap solution for non-lead batteries.

I have a factory DC regulator between my main battery/alternator and the second chassis battery. It charges the second battery somewhat after the primary starter battery is fully charged. Off of that secondary chassis battery I have an isolator like the ones listed on Amazon above that connects 2 additional chassis batteries.

It works great keeping the dual spares charged up, and if I accidentally run down the main batteries I press a button and the dual spares come on line to start the engine.

None of these are connected in any way to the LiFePo house battery right now, but I have a Renogy 20A DCDC charge controller which will provide the right charge profile for the LiFePo battery when I'm driving.

[john61ct]

The whole point of an ACR is to eliminate human switching.

Your sources go to your primary battery, direct and all at once.

The ACR takes that circuit as input, and when that circuit has a source go active, i

ts output goes to your secondary battery.

That is all, easy peasy.

[dbsoundman]

Originally Posted by john61ct

The whole point of an ACR is to eliminate human switching.

Your sources go to your primary battery, direct and all at once.

The ACR takes that circuit as input, and when that circuit has a source go active, i

ts output goes to your secondary battery.

That is all, easy peasy.

Problem is I only intended for 30 amps of charging from the alternator, not “whatever I can get”, so I only used wire sized for that amperage. Other “kits” I found online used 2/0 from the alternator to the house batteries and I can’t fit that through my pass-thru hole.

[Rucker]

Originally Posted by dbsoundman

Problem is I only intended for 30 amps of charging from the alternator, not “whatever I can get”, so I only used wire sized for that amperage. Other “kits” I found online used 2/0 from the alternator to the house batteries and I can’t fit that through my pass-thru hole.

What do you have for a house battery?

[dbsoundman]

Originally Posted by Rucker

What do you have for a house battery?

Currently, 2 200Ah AGM batteries. But I built my system to be somewhat future-proof to support Lithium if I decide to go that way in the future, which is another reason why I really wanted to run all my charge sources through the charge controller - trying to keep it simple.