Does a Battery to Battery Charger Need an ACR too?

[Tbacus]

I am looking to wire a Sterling Battery to Battery charger in my Sprinter van. My questions is, do I still need my old Automatic charge relay ( I use a Blue Sea ACR) or does the Sterling charger do starter isolation?

 

[Joe917]

The Sterling does not require ACR.
It monitors starter battery voltage and does not connect until it senses starter battery is receiving charge from alternator and charged.

 

[john61ct]

Yes DCDC chargers generally perform the same function as VSR/ACR, just with a lot more intelligence (and highr cost)

Depending on bank size and battery chemistry vs charger Amps, best to put all charge sources including alternator to the bigger House bank, and use the DCDC charger to feed the smaller Reserve/starter.

Have you purchased it yet? Why do you need it?

 

[Joe917]

Depending on bank size and battery chemistry vs charger Amps, best to put all charge sources including alternator to the bigger House bank, and use the DCDC charger to feed the smaller Reserve/starter.

Not recommended. The Alternator should stay charging the starter battery. The alternator is designed to recharge a starting battery.
The B-B charger will not load the starter battery(actually the alternator through the battery cables) until it senses the starter battery at full charge.
If you reverse the b-b set up you could well get the situation where the house bank never gets full charge (short drive times) and consequently the B-B charger does not engage to charge the second bank, in this case the starter battery.

 

[dwh]

You can't use a B2B and an ACR together. It creates a feedback loop. The output of the B2B gets looped back around to its input through the ACR.

 

[dwh]

Depending on bank size and battery chemistry vs charger Amps, best to put all charge sources including alternator to the bigger House bank, and use the DCDC charger to feed the smaller Reserve/starter.

Not recommended. The Alternator should stay charging the starter battery. The alternator is designed to recharge a starting battery.
The B-B charger will not load the starter battery(actually the alternator through the battery cables) until it senses the starter battery at full charge.
If you reverse the b-b set up you could well get the situation where the house bank never gets full charge (short drive times) and consequently the B-B charger does not engage to charge the second bank, in this case the starter battery.

Yup.

Also, the B2B bucks up the input voltage to a higher output voltage to do a multi-stage charge on the house bank. Running the alternator to the house bank and then using the B2B to do a proper 3-stage charge on the starting battery would be somewhat pointless.

 

[dwh]

dwh must be on MPPT overload.:costumed-smiley-007
Battery to battery charger boosts voltage. A buck lowers voltage.

Oops.

Stayed up too late last night and my first cup of coffee still hadn't kicked in when I wrote that. The worst part is I meant to say "kicks up"... "bucks" snuck in there when I wasn't looking.

 

[pdxfrogdog]

You can't use a B2B and an ACR together. It creates a feedback loop. The output of the B2B gets looped back around to its input through the ACR.

I've got a dual battery tray under the hood which uses a Cole Hersee 48530 isolator. I'm interested in running a B2B at the rear of the vehicle to charge and maintain a 3rd house battery. Is this doable or will I run into the same scenario above? I'm interested in the B2B (ctek d250) as it can charge my house battery while driving and includes a nice mppt solar controller for use while parked.

Edit: the dual battery tray is from genesis off-road

 

[pdxfrogdog]

If you exchange your Cole Hersee with Ctek D250, & its output serves both house batteries, It will work if you can live with Ctek 20amp limit. (and its insane pricetag !!)

But if you plan to use front house battery to supply the Ctek what then charges the rear battery.
There are a couple scenarios to define.

1, If the two house batteries are separate "house systems" this works. (But 20amp max.to rear battery...)

2, If its to work as 2 house batteries combined. One will need a method to bypass Ctek combining the house batteries, What sort of renders Ctek moot except for its neat voltage boost charging feature.

The scenario I am hoping to achieve is that the dual battery system up front remains unmodified and the Cole Hersee isolator does it's thing to automatically combine and separate based on voltage. This under-hood system supports hard mounted accessories such as lights, radios, winch, etc and gives me redundency for starting (The genesis tray includes a switch to combine batteries regardless of voltage if needed for starting). At the rear, a separate house system in a removable battery box would be charged by the Ctek when driving or when the solar suitcase is deployed. I only have 8 gauge to the rear of the vehicle so the voltage boost function seems useful. These are all parts I already have lying around, so my main concern is would there be any issues just connecting the Ctek up to the existing rear wire that sits on the genesis tray's accessory bus bars?

 

[dwh]

No problems then. Just use Ctek as would any other isolator. Its input supply coming direct from the alternator.

Agreed. You can't use both split-charge relay (ACR) and B2B together to a single aux battery, but to two independent aux batteries - no problem.

And also agree to feed the CTEK straight from the main battery and NOT by tapping off the underhood aux battery after the power has already run through the ACR. That way the two (hopefully) don't do anything to affect each orher's operation.