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. :rolleyes:

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 :D

Dave,

Priorities, right? :D

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.

Not to derail the thread but can you tell me more on your set up? I also have a LIFEPO4 "house" battery and not sure if my current standard charger will work, (seems to be for now but I`d rather not kill the battery) I also have a ACR

Dan,

By all means…. Derail away. This is a discussion forum. I’ll gather the info as you do. All good.

Thanks. Brad.

Guys,

FWIW, I think I’m good. Just put two solid days on our boat, and the charging system seems to be keeping up just fine. The batteries metered at ~12.7v after both days of running. The volt
meter just lies. :rolleyes:

Thanks. Brad.

Grock says the safest bet is to use a DC-DC charger and I don`t need the ACR I put on .
Seems like I over designed it.
https://cimg3.ibsrv.net/gimg/www.off...70085a03fb.jpg

I just bought a lithium battery for my street car. Was told NOT TO RUN a regular battery charger not designed for lithium battery. It will damage the battery. A regular charger lowers the voltage as the battery is charged. A lithium charger merits raising the voltage. With lithium charger i bought, it did in fact keep raising the voltage as the battery is charged. When the battery was fully charged, it was at 14.4v. That was info from feather lite battery tech. After sitting the battery went down to 13.6v.

I have been using these battery chargers in both of my boats. You can set each bank to the type of battery being charged. It does a good job on the lithium battery in my bass boat that runs the electronics. Charges it to 13.8V. I also have one for the 36V lithium for my trolling motor, it charges to 38V

Dan,

How would you plan to charge both batteries while underway without the ACR?

One of the interesting side effects/benefits I wouldn't have thought of until it was presented to me is that, with an ACR, there is no need for a tandem battery charger for basic charging on the trailer; the ACR will automatically close the circuit and charge both. For conditioning, I will need to trip the breaker in the ACR bridge circuit, or the tandem charger won't recognize separate batteries.

Thanks. Brad.

Brad,
The engine charges the starting battery, the DC-DC charges the LIFEPO4 battery basically on its own circuit from the starting battery .
I thought using the ACR would help if the DC-DC charger started to drain the charging battery when engines aren`t running but Grock does not like combining the 2 different voltages and the ACR would combine both.
I solved that by getting a DC-DC charger that will automatically shut off once the incoming voltage (from starting battery) falls below a certain threshold.... via bluetooth control.

Dan,

Gotcha. It's a "one or the other" scenario. :cool:

Thanks. Brad.

Sorry, I was out of town and missed this.. It seems like you have something similar based on the previous responses, but here's my "plan".. not in the boat yet, but its the plan..
I will have a standard 12V lead-acid start battery and a 12V LiFEPO4 house battery. I have my new high-er output alternator (105A) going directly to the start battery. I then have a Victron 50A Orion XS DC-DC charger between the start battery and lithium battery. The input is hooked up to the start battery, and output is hooked up to the lithium. It is configurable for different battery chemistries, so mine is setup to charge lithium per the battery recommended parameters. This is a one way charger, so it can only connect input to output and not the other way. Like yours, it by default will turn on when it detects a high enough voltage, however, I'm going to be setting mine up to only turn on when the key is in the "ON" position with a 30 second delay. I'm doing this because I plan to hook up a small solar panel to keep my start battery topped off when I'm away from the boat and I don't want the solar charger to trick the DC-DC charger into thinking the engine is running and sucking power from the start battery. I will also have a Victron inverter setup to charge the lithium battery only from shore power.
I have a express cruiser, so I plan to maybe spend a night or so at anchor, so overkill for a go-fast boat, but the same logic still applies to a start-house battery setup for you guys if you go to lithium, just minus the big inverter.

The biggest downside to the setup I have is I'm limited to 50A of charging, but I'm okay with that because thats about 50% of my alternators rated output and there will be some base running load, so maybe 60% loaded?? I feel much more comfortable with that than trying to pull 100% of its rated output the whole time my boat is running trying to charge the lithium battery.. The biggest killer of alternators is heat, and the fastest way to heat it up is running at full output and low engine rpm (low speed cruising) because the fan is not doing its job...
If you want your alternator to last as long as possible, run the engine wide open and limit its output to something less than 100%... If you want to go above and beyond, I plan to have 1 of my 2 engine compartment inlet vent hoses running right next to the alternator, so the fresh intake air is hitting the alternator when the blower is running, which I usually just leave on when the engine is on.

Thats probably way more info than you wanted, but thats my plan lol

Between putting in engines thats pretty much what I did lol
My DC-DC charger is bluetooth and I can change the voltage at which it shuts off and turns back on deending on the voltage it receives from the start battery.
I have found it draws a ton of power and lowers the voltage in teh start battery FAST.
, I set the turn off voltage at 12 and back on at 13v . That way it pretty much doest charge unless I`m plugged into shore power or the engine is running .
I put the charger on a switch so that it can just be turned off , lets say after draining the lithium battery I don`t want the alternator to over heat as mentioned.

https://cimg1.ibsrv.net/gimg/www.off...915a51f239.jpg

also installed the Eddie Young recommended Weldon 2025 fuel pump. Does not come with any mounts so keep that in mind .
Got rid of the A1000`s .

https://cimg2.ibsrv.net/gimg/www.off...1d522d317a.jpg

Dan,

That looks very much like the one I’ve got. Mine is fairly loud. LMK what yours sound like when you get them up and running. I’m pretty well set on replacing it this winter, but I might try and rubber mounting it first.

Thanks. Brad.

Will do ... can`t be any louder than the A1000`s , they were loud but can`t hear em over the engines once started .