Understanding how ACR works

[mikeo16]

Thinking about adding an ACR to my boat to charge my reserve battery, but wanted to fully understand what happens when my house bank fails. Questions:
* Does ACR current flow in both directions (whichever bank is lower get current passed to it?). If so, then if house bank suddenly fails, will reserve bank drain attempting to pass current to the house bank?
* if all charge sources are directed to the house bank, how does reserve bank get charged when house bank has failed?

[transmitterdan]

There are multiple types of ACR. Some send power only one way. Some send power both ways. Some have a manual override so you can control when it activates for emergency start situations. So you can have whatever type you need.

[transmitterdan]

Generally an ACR will disconnect if the battery receiving charge goes down in voltage. This prevents discharging the reserve bank if the charging bank goes “bad”. But most batteries don’t fail short. So if the charge source is active the ACR will still send current to the reserve bank.

If the primary charge bank is truly bad then disconnect it and short out the ACR until you can get new primary battery.

[mikeo16]

Thanks, that's just what I was looking for- much appreciated. I didn't realize there were different Blue Seas ACR models to choose from so need to do a little reading up.

[john61ct]

The ACR only closes (joins) when a charge source is present, opens when it stops.

And your job is to replace your House bank long before it is anywhere near failure, not something you should plan on happening.

If if did, you would just disable the ACR and only use Starter to get back to civilization.

[mikeo16]

Thanks John and yes I agree. I am just trying to plan the worst case scenario. I would expect that over time the house bank will be replaced at different time intervals than the reserve bank, but I tend to be prudent on replacing batteries before total failure would occur.

[Cat36Mahalo]

Most ACRs won’t charge battery to battery. All chargers should go to your house — Alternator, shore Charger, solar, and wind. When the voltage on house is above a fully charged house ie tyhere is a charging source it connect to remote battery.

[Rapanui]

You require a Voltage Sensitive Relay which works by allowing current through when the voltage is above a threshold say 13.8 V and disconnecting at say 12.8 volt although there are programmable versions. If a battery fails short then no current should flow so you will not discharge the good battery. You can get ones that work both ways charging if either battery has charging. Does require that both batteries have a compatible charging regime

[sailah]

I have all charging sources, and loads like panel, connected to my house bus. My blue seas ACR also connects here. My house bank connects to house bus with a on/off battery switch so i can isolate. I don't have same arrangement on my start although i could easily pull the cable or fuse.

This is my first season wiring my boat this way with ACR and buses. With all charging to house and ACR taking care of start bank. I love it and can't believe i waited this long.

[john61ct]

VSR and "combiner" are generic synonyms for ACR, which is what BSS uses.

Best unit hands down is their ML 500A https://www.bluesea.com/products/762..._-_12V_DC_500A

bulletproof, will last longer than any vehicle, pass it on to the grand kids

[mikeo16]

Wow, thanks for everyone's input - this very helpful !