Under,

And which battery would that be? The one that’s powering the ECM or the one that’s not?

With the mandate that the ECM be connected directly to a battery, there is no choosing which one is getting charged at any given time, unless you’re either just going to run until the battery powering the ECM is dead and then call for a tow or hope the one that’s not is charged when it comes time to start back up at the end of the day.

It may be that I need more alternator. That’s why I’m having this discussion. But this is exactly why the ACR exists.

Thanks. Brad.

Liberator221,

Gotcha. My list of winter projects is piling up.

Thanks. Brad.

You leave the boat at Cumberland all summer?
Thats nice but inconvenient for taking care of these little problems. Congrats that it’s running well.

Liberator221,

Typically not. We usually keep it at home, in Dayton, in my shop. We spend far more time on it at our local overgrown mud puddle than we do on Cumberland, sadly. This was just a case of life and schedules imposing their will, and the executive decision to not tow it back and forth so much when we were going to be on Cumberland all but one weekend in July. We’re bringing it home after this weekend. Not even sure we’ll be back down until the PokerRun.

Thanks. Brad.

The other one is shinier so that's my vote

Dave,

Priorities, right?

Thanks. Brad.

You're fine charging both batteries off your current alternator.. An alternator is self-limiting, so its not like batteries can "pull too much current" from the alternator.. It can only output what it can output.. In your case around 65 to 70 amps..
Now there IS validity to the concern of overloading an alternator at low rpms.. If your doing a lot of idling around or low rpm cruising, you can overheat an alternator because its internal or external fan is not sufficient to keep it cool under low rpm charging.
With your ACR, you should be good anyways because if you have it hooked up correctly, it should be going from your start battery, to your "house" battery so once your start battery is full, it will start charging the house battery. So your initially only charging one battery anyways until the start battery is topped off. You don't have any need for any fancy charging gadgetry for your current setup..

I went to lithium for my house bank, so I had to get more intricate with my setup since I'm charging too different battery chemistries, but your lead acid batterys are "dumb" and take whatever you throw at them.

AShipShow,

Again…. Keep in mind I don’t have it rigged as start/house batteries. It is batt1/batt2. I’m not sure if this makes a difference when you describe how the ACR works. Near as I can tell, the ACR just makes it so that the two batteries are “in parallel” when it switches to closed circuit. Just want to be sure.

Also, just to be clear…. As I understand it, when you say that LA batteries just “take what you throw at them”, that’s assuming you are throwing more volts at them than they are currently putting out, correct?

Thanks. Brad.

Guys,

Interesting discovery…..

Got to the house on Cumberland, crawled up in the boat to survey the state of the batteries. Two weekends ago, during their girls weekend (using a friend’s boat), the CFO had put one battery on charge for a couple days, then switched to the other, and left it for the last two weeks. First discovery was that both batteries metered at 13.7 volts. Then I detected a subtle whine/hum from the engine well. I turned the batteries off, but it persisted. Thinking it was either the ECM or the Mercathode, the only two things connected directly to the batteries, I disconnected each battery one at a time. Neither eliminated the hum. Sticking my head in every nook and cranny of the engine well, I eventually tracked it down to the ACR. As soon as it saw anything over 13v for at least 30sec (according to their documentation), the relay kicks and bridges the two positives. So the battery charger was actually charging both batteries. This explains why both were topped off after two weeks with one of them not connected to a charger. But this also means the relay will slowly discharge both batteries until they are both below 13v, then open. Tricky….

Thanks. Brad.

a battery at resting state (no load and the surface charge burned off should be around 12.5-12.8 volts at full charge). if you disconnected the charger and checked them then they will show up like you saw. if you wait an hour and check again they will probably be in the 12 volt range. that is why the ACR cuts in and out around the 13 volt range as it should never see that until the alternator is working.