12V71N Charging Question

[Sparky1]

This is a question I've been meaning to ask ever since I brought my 58 from FL to TN last year. During the latter part of the trip, my voltage would drop significantly on the one running engine. In fact, after an extended run on one leg of the trip, I actually had to use the parallel switch to get enough voltage to kill the engine.

While dockside or running the generator, the charger would bring the battery back up, but the same scenario would play out as the day wore on. There was no DC being used on the boat while cruising, so what the heck is pulling that battery down?

 

[bigbill]

randy, maybe bad batteries that are discharging themselves. how old are they?

 

[SKYCHENEY]

Which engine? Which battery bank? House or start side? Is it the OEM setup or did someone change things around?

 

[Sparky1]

I hate to be stupid, but I'm not sure how these batteries are wired as to which is the house side. As for it being original, who knows?

The battery for the starboard side is disconnected to prevent any accidents, but it's still hooked to the charger. As a reminder, I was running on the port only. All the batteries appear to be in good shape, and all cells were up to the appropriate level of electrolite.

I have no idea how old these batteries are, but they fired the engine after about an hour on the charger having sat for almost a year. BTW, the charger I'm using is a manual with a timer, and it came with the boat. The automatic charger doesn't work, but I haven't tried to troubleshoot it.

 

[Boatsb]

Just throw down on a new alternator. I found one on line for you cheap if you want. They may have 2 so get one for each engine.

 

[SKYCHENEY]

Randy,
Usually the port bank starts the port engine and also doubles as the house bank. This mean that your lights and heads and any other house accessories are probably pulling off of this bank.

 

[Sparky1]

Sky, keep in mind I was running during the daytime and using no DC whatsoever. As for the other bank of batteries pulling down the ones hooked to the port, that couldn't really be the case since I could parallel off that bank and either kill or start the engine.

Correct me if I'm wrong, but it's my understanding there is no need for DC power on these engines except to start them. If these were gassers or had electronic fuel injection, it would most likely be an alternator problem, and the engine would quit when the battery power went south. What am I missing here?

 

[ThirdHatt]

Randy, it sounds like you may have a dead battery within the bank or an entire bank that is getting weak. Sometimes they can be brought back with a good charge as you stated and start the engine, but other times they will show fully charged yet not have quite the muscle needed to spin the motor adequately.

If those batteries were not almost new when you got the boat, they are probably about due to be replaced. Take a good look at them next time you're on board and you should be able to find the date code stamped on them. Unfortunately, unless you have Rolls-Surette ($$$) batteries, 3yrs is when you should start to wonder about the batteries and if you squeeze over 4 yrs you are on borrowed time. The older ferro-resonant chargers that came with our boats are hard on batteries as well and can contribute to shorter lifespans.

One way I like to tell how my battery banks are doing is to shut off the charger for at least an hour before starting, but preferably overnight as long as you are sure there is no stray DC draw. Then, hold the "shutdown" button and press and hold the start button. Watch the voltmeter and listen closely to see if the volts drop off more than the initial hit or the engine begins to spin slower after the initial couple of seconds. A healthy battery bank will spin those motors quickly and not slow down. If your bank is not 100%, then you can see the voltage drop off and hear the spinning slow down.

Hope this helps!

 

[REBrueckner]

Third Hatts battery test is one way.

Another is to charge the bank in question, lift the positive terminal with all accessories OFF...any spark as you touch cable lug to terminal?? if so something is, on maybe drawing battery down.

Or just, lift the terminal off and leave it off a few hours...check each cell with hyrdometer....up to 1260 or so?? if not, replace battery...

Most likely, a battery or batteries are old and tired....your symptoms are classic for that situation....I had less severe situation this fall....checked with hydrometer, found a flat dead cell in one of two 8D's...that's enough to keep engines from turning over....

 

[Boatsb]

Charge them all good and disconnect them from everything. Then wait 12 hours if possible and check every cell for consistency and level with the hydrometer.

 

[yachtsmanbill]

Hey Sparkolito... Doesnt the voltmeter work on that side??? ws
http://www.isspro.com/proddetail.php?prod=R8762

 

[egaito]

You say there was no DC in use, but what about the heads? Or was it "head" for that trip? Autopilot? Electronics or tunes? Whenever we're out, there always seems to be something on somewhere.

Weak batteries of course, are a real possibility if they're a few years old. The charger might bring them right back up, and maintain them as long as loads are light, only to have them die off quickly as soon as the charge is removed.

 

[Sparky1]

Bill, the voltage meter on the starboard doesn't read. I'm assuming it may be because things are disconnected on the engine. It's been so long since I ran both of them, I don't remember what worked and what didn't. There's no doubt the starboard batteries are hooked to the charger and do in fact take a charge. Otherwise it wouldn't do anything when I used the parallel switch.

Ed, my heads are 12V Vacuflush as is the case with all my electronics which work off separate batteries that are maintained by onboard chargers. This problem never occured until the final leg of my trip after the boat sat at a private dock on Pickwick for a couple of months. Even when I took it from Hales Bar to Chattanooga and back this past May, I didn't have any problems.

I ran the boat for about 4 hours, shut it down for a couple more, then it fired right up for the return trip. I'll try testing the batteries next time I go down to the boat. No doubt I really do need to get the automatic charger/converter fixed or replaced as I'd be SOL if she starts taking on water with no voltage for the bilge pumps. I have some folks who live aboard their houseboat docked right next to me, and they're good about keeping an eye on the old gal.

 

[SKYCHENEY]

Bilge pumps are probably running off of the stbd (non-house)bank.

 

[bobk]

Randy, I'd bet on tired batteries. Been there, done that. My first clue was seeing the voltmeter drop way down when starting. Not much later 'nadda' unless I used the parallel switch. Four new 8D's later and all is well. The old set did last five years though.

Bob

 

[dwaynec]

Randy, I too concur on there being a battery problem. Had that same problem earlier this year. Also sounds like you may have an alternator/regulator problem. I had that problem this year too. Troubleshooting is easy since you have spares already on board. I am assuming that the alternator and regulator from the stbd engine work. Just try hooking up the stuff from the stbd engine to the port engine. Maybe an hours work. That is how I found out my regulator was bad.

FWIW. My batteries were seven years old when they finally wouldn't hold a charge. That is with the LaMarche ferro-resistant charger on the boat. Go figure.

 

[Sparky1]

I'll be down at the boat again this week-end so I'll see what I can figure out. The first time I knew I had a problem was after I had run the boat for 8 hours or so on that last leg and saw the voltage at around 20. By the time I'd finished that day's run, I had to hit the parallel switch just to kill the engine. Thank God that worked or I would have been forced to pull the emergency stops.

I stopped by the boat briefly last Saturday and set the charger for 9 hours. It will be interesting to see what kind of reading I get when I go back. I too assume there is a problem with the alternator/regulator or I'm assuming the voltage wouldn't have dropped while the engine was running, even with a bad battery. It won't be possible for me just to hook things up to the starboard since it's not running, but I can certainly test the alternator to see what's going on with it. I'm not sure where I'll have to go to find 8V batteries around here, but maybe NAPA carries them.

 

[dwaynec]

When the alternator on my port engine quit charging, I pulled it and took it to the shop. The shop tested it and said it was good, so I reinstalled it and pulled the regulator and took it to the shop to be tested. Shop says it is good and they set it to regulate the voltage to 14V. Back to the boat and reinstall, start the engine and NO CHARGE. Pulled the regulator from the starboard engine and installed it on the port engine. Alternator started putting out about 13.8V. Next stop was NAPA and purchased a new regulator. Now both engines put out between 13.6 and 14V. Seems the regulator checked out ok on the test equipment, but wouldn't work on the boat under a load.

 

[Sparky1]

I took another trip to the boat this week-end, and there's no doubt I have battery problems. Looks like I'll have to replace the batteries before I can test the alternator as there is no way the engine would have started with the batteries that low. Cold weather really tells the tale on weak batteries.

Now that we've gotten that out of the way, does anybody have any suggestions for batteries?