Battery reading 14V+

I've got the inverter using bank 2, which is an 8D battery. Bank 1 is a pair 1000 CCA truck-size batteries. Bank 1 is clearly almost new, Bank 2 could be 15 years old for all I know.

The inverter/charger is powered on, so it should be covering the basic house loads, which at this point are just a few lights most of the time. It appears to be working, mostly the "float" light is lit but it goes to "accept" from time to time, and "charge" after I put a load on for a while with the shorepower off. I can switch the house loads between bank 1 and bank 2.

Bank 2 is reading 14+ volts at the power panel. Bank 1 shows a little high at 13+ volts, too. I figured maybe the inverter's gauge was a little off, and maybe the inverter was putting out the 14+ volts to power the house loads.

Then I went to start the engines for the first time this season. One is on bank 1, one on bank 2. Neither one turned over fast enough to start. One at a time, I threw the selector switch for each engine to "all" and the starters spun right up and started immediately. Also, with the engines running, the analog voltmeters agreed with what the inverter was telling me (14+ and 13+ volts.) I'd expect that at first, but I ran for an hour and the meters didn't go down much.

This leaves me with three mysteries:
- Why is the voltage 14+ on one bank?
- Why 13+ on the other?
- Why, after being on the charger for weeks, didn't they start the engines alone?

I'm prepared to believe Bank 2 is just old and needs to be replaced. I plan to replace it with 6 golf cart batteries first chance I get anyway. I suppose Bank 1 could have not been getting a charge because the inverter/charger is not set up the way I assumed it would be (charging both.)

Still, I've never seen a battery voltage that consistently high.

"Why, after being on the charger for weeks, didn't they start the engines alone?"
There is nothing left!

Batteries that are 3X their service life will show high voltage on charge as the charger makes up for decades of internal problems.

To trouble shoot , disconnect the chargers 24 hours then measure the V AT the batterys.

While your there have someone crank an engine and see of the voltage drop is at the batts , or in the wiring.
IF the drop at the batts is not bad (11V or better cranking) switch the V meter to the starter terminals and see what you have.

Usually 10V cranking at the starter is required.

"I plan to replace it with 6 golf cart batteries first chance"

To start usually START batts do a far better job than deep cycle batts , unless you have a big bunch of them, then its fine.

THanks FF! I hadn't seen that symptom (high voltage on charge) before, but I never let a battery get 3x its service life before, either. I think your troubleshooting suggestions are the right place to start.

I don't think the PO (who only owned it for a year or so) had a strong electrical background. And the 8D does look like it's pretty old. I'm now wondering if the other starting bank was even connected to the charger. Or maybe the selector switches are not wired the way I think, and both engines were trying to start off the same bank. This is going to drive me crazy until I can get down there next w/e to check.

The PO of my boat had the big cables all mixed up so that when I thought both banks were isolated from each other, they were actually paralleled. I took a long period of head scratching and a failed set of batteries for me to figure it all out. Once I dove in there and traced the cables, it all made much more sense. Replacing the batteries and cables, reconfiguring the alternator charge path and adding the appropriate switches, combiner and battery monitor solved all my problems.

You don't mention if you have a battery isolator wired in somehow. loss of nearly a volt is common across an isolator. Some people try to account for this by placing the sense wire going to the alternator on the output side. First thing I would want to sort it all out is a first class digital meter. With 12 vdc a difference of a tenth of a volt is significant. Don't let a cheap meter give up that much in accuracy. In my mind having a multiple bank charger charge batteries of much different capacities and ages never works well. I think you are absolutely right throwing the whole thing away and converting to 6v Golf carts. Good Luck with your battery project. I am doing the same thing as well.

Good point, the entire boat was professionally re-wired not that long ago, and everything looks very good. But it will take me a while to trace everything down and figure out how it all REALLY works. I do have a professional quality Fluke meter that's been very helpful so far.

I wasn't focused on the battery system since it all worked fine during sea trials and some basic testing of the system, such as switching loads to and from the inverter and the two banks. Now I'll be digging deeper.

OK, the results are in - partially.

Bank #1, with two sealed 1,000 CCA commercial starting batteries in parallel, isn't hooked up to any charger. And at one point the selector switch for the house loads was set to "1". The engines hadn't been run all winter. That explains why it was weak.

Bank #2, one 8D battery, was low on water. THREE GALLONS low. I've never seen a battery take that much water. It charged for a few hours and was on the float stage when I left. Next weekend I'll run the equalizing routine on the charger, but even if I can bring back some life, it will be replaced.

I was surprised there's no way to charge bank #1. I have a Heart Freedom 20 inverter/charger, and I found where in the manual it actually states there's only one charging circuit on the model 20.

For a test, I set both engine selector switches to "all" and left it that way for a couple of hours, thinking it would force some charge into bank #1 via the charger hooked to bank #2. It seemed to work. After all this, both batteries were able to start their respective engines.

I'm thinking about installing an old 2-line 30A smart charger I have and wiring it to bank #1 and the genset starting battery. I'd keep bank #1 as the starting bank with two 12V batteries, and fill up the rest of the battery compartment with 6-8 golf cart batteries, for a 660 to 880AH house bank.

From what I have read, once the battery plates in your 8D were exposed to the air, the battery is toast.

Golf Cart batteries are a respectable and inexpensive way to have a good house bank. Lots of cruisers use them and they are readily available.

I would caution away the idea of hooking a charger to the genset battery and the Engine start battery (bank 1). You could create a path that would allow a dead engine battery take the genset battery with it. My genset battery is hooked to nothing other than the genset. It is a good, fresh battery that I want completely independent from the other batteries. The genset is the power source of last resort. When it starts it can charge all the other batteries. If I was away from the boat for an extended period of time and I was concerned about the genset battery state of charge, I have a portable 10 amp charger I can hook to it powered by shorepower. I also carry a set of jumper cables. But I have never used either the portable charger or the jumper cables. I hope to keep it that way.

The Heart Freedom series has (I believe) only one three-stage (smart) charger connection. Howver some models can accomodate one or more echo chargers. These are float charge only. They will recharge a battery and hold it at charge but the recharging time is longer than the three-stage charging circuit. I believe the Freedom 20 can accomodate two echo chargers.

Usually the smart-charge circuit is connected to the house battery or bank since it is the one that will get the most use and largest potential discharges and is usually the battery or bank the inverter is connected to. The echo chargers can be connected to the start battery and a generator start battery if there is one.

This is how our boat is set up.

but even if I can bring back some life, it will be replaced.

Be sure to drag the old dead batt to the batt store , its worth about $50.

Yes, I read that about the echo charger in the manual, but the inverter is in a dark closet and I didn't see any place to connect it. I'll look closer at the manual and try to crawl in there with a light and magnifying glass, that would be perfect for the genset.

The "old" charger I have (twenty years newer than the boat!) is set up to charge two completely separate banks. I suppose it could fail internally and set up a path between the two systems. I could just wire it through a switch and only use it if needed. I do like the idea of keeping the generator system isolated.