32 volt charger/batt'y problem

[doc g]

Got to the boat tonight and found that ever so lovely stink of battery in the stb engine room. Batteries were hot about 110-120 degrees , charger was hot and running,batts are very low on water. Charger is a relatively new Pro Mariner 32v/220 v input. shut down charger and watered batts ,each took about 1/2 gal. These are Rolls 8v with the low maintenance caps. I think I have a short in one of the cells. The port bank of batts appears to be fine ,not hot or stinky. Question is how do I determine which cell(s) are bad and how do I rule out the charger as possibly the cause of the problem. I assume if the port bank is ok then it's not the charger,right or wrong? What is the fully charged voltage of an 8V batt'y? Any help would be greatly appreciated!!!!......................Pat

 

[yachtsmanbill]

I just installed a new charles charger--30 amp 32 volt on 110. Most of my submerged batteries came back. Starting bank is at 32.5 but house bank sits at 25.5 that means one bum 8 jolter.180 bux from Interstate.The charger itself runs a steady 33 volts(ish ) but I am constantly testing systems etc like re-doing twisted wires and lotsa gooey tape residue from the SPO. You can disconnect all the batts for a load test or test each cell with a hygrometer to find the culprit.Should be about 2.2 volts per cell fully charged. I still need 1 alternator. Got a quote of around 475.00 at cost for a new one. Internal regulator instead of that flash gordon business downstairs LOL. Being BANAL like I am, I always disconect shore power and water when I leave. Bilge pumps are on hot side of main switches but thats it. Make sure packing glands are good !! Rain shouldnt sink a 50 foot boat.Sounds like you have a shorted cell to make it overheat and dry up like that. Let me know what you find as I am sure that I'm in for some surprises too !!! HATTRICK Willy

 

[Genesis]

Yeah, probably a shorted cell. This is a bad news scenario for a charger as it never sees enough voltage to get out of "bulk" mode, and boils the bejeezus out of everything else.

Get out the voltmeter, it should be easy enough to find....

 

[Nonchalant1]

Pat,

Not sure it sounds like a battery problem because bad batteries most frequently cause the charger to turn off without fully charging the bank, but you can find out.

First check to make sure you don't have a short or power circuit stuck on. If your pre-heat switch for your genny, for example, was stuck in the on position, you'd be draining your batteries fast, heating or burning out the pre-heat elements, and running the charger non-stop to try to keep up with it.

If there's no load on your batteries. Then check to make sure that if you have a sensing wire from your charger that it is OK. If the voltage sensing wire is disconnected, your charger will run forever trying to reach the shutoff voltage that it is set for. If your charger were just continuing to run, you'd get the condition you described.

Next, after the batteries have been watered and had time to equalize for a few hours, turn on the charger and watch the voltage between the battery bank's + and - terminals. A fully charged bank will be reading out over 37 volts. A badly discharged bank will read out under 32 volts. If the bank reads out over 37 volts with the charger on, it should be shutting off.....why isn't it?

If the charger is working OK, or if you want to start with the batteries, then use a multi-meter to check the voltage between the + and - terminal of each battery. If they're charged, they should read 9 volts or so, but the key is to see if one reads much lower than the others. If 3 are at 9.2 volts and one is at 6.4 volts, that's the bad battery.

Then get a hygrometer, the kind that measures specific gravity NUMBERS and check each individual cell in each battery. If the batteries are charged, it'll probably be around 1250 or so. There should not be a cell out of range with the other cells by more than about 10 points. If 3 cells are at 1245, 1250 and 1250, and one is at 1200, that's a dead cell. If you find one battery with one or more cells out of range, call your Rolls dealer and find out what they want you to do. If so, they'll probably have to call the factory because these batteries hardly ever go bad and some dealers have never handled one bad battery, but Rolls will stand behind them completely.

Doug Shuman