Battery Charger Rapidly Turns on and off

[ritchievail]

Last night I entered the port side engine room of my 1973 53MY and when I turned on the engine room 32v light the battery charger came on. In the beginning this did not seem like a big deal, but as time went on I noticed that the charger is actually running every few seconds. It will run for 4 seconds then pause for 4 seconds. This happens when I turn on 2 32v light bulbs? Strange, so with the time provided I turned off that light and turned on another in the aft state room, this one has only one bulb, same thing.

What do you think might cause a battery charger to do this?

I checked the water levels in my batteries about 1 month ago and everything seemed fine. Could it be that I was mistaken about the water levels and now I am baking my batteries?

Has anyone had this problem? Is this my battery charger waiving goodbye to me?

[MikeP]

Is this the old, original LeMarche Charger? If so, there is a lengthy thread SOMEWHERE here, though I couldn't find it, about problems with internal connections on my leMarche which cause the kind of problem you are describing. I disassmbled/cleaned the connections on mine last year or the year before to resolve similar problems. I'll keep trying to find the thread...

[ritchievail]

It does not look like original equipment. I am not at the boat, but I will try to describe it without having the name.

It is white and roughly 18" wide and 22" tall. It has 2 lights on the front one amber one red. There is a small gauge with a small rocker switch, right for manual and left for auto. I will post the name when I get home this afternoon.

Thanks!

[REBrueckner]

Good for you!!! You notice how your equipment functions and notice when a change occurs....BRAVO, you are already ahead of 99% of boaters....

It's either the charger or your batteries. Check the specific gravity of each battery cell ...preferably after you have shut the charger off overnight...but a dead cell will usually show up even with the charger connected.

A load test: turn each engine over via starter with fuel shut down activated to prevent starting...(do NOT use your battery parallel switch) does the port engine turn over slower than the stbd? assuming they have the same number of batteries, say a pair of 8D's, if you can hear a difference in crank speed the slower one has weak batteries.

When I checked in December, I found my port engine did not crank/turn over as expected...a hydrometer test showed one dead cell in a pair of 8D's...Will be replacing both those 8D's next week before spring commisioning.

[ritchievail]

REBrueckner,

That's a great start.

FYI--the Admiral emailed (she follows the forum too…I am a lucky man!) and let me know that it is a Sentry charger.

I am afraid I have not done my due diligence and I will be replacing a battery or two myself.

Ill post my findings.

[DAlter]

You may have an adjustment inside the unit for "Cut In" and Cut Out" voltage. In my charger they are two potentiometers that require a small screwdriver to adjust them. I've had mine change a couple of times due to vibration. Check your owner's manual for instructions.

[Nonchalant1]

That's a symptom that indicates it could also be sulphated batteries. I would guess that the bank may not be able to provide as much power as before also. When batteries are cycled, as in marine use, they can develop hard sulphates which will not accept a full charge and will return a higher voltage reading, which fakes out your charger. Here's how to find out.

Get your handheld multimeter and set it so you can see batteyr voltage to at least one decimal place. Hook it up across from the main neg to the main pos terminals with everything off, including the charger. Note the reading. Now turn on some 32V lights and turn on the charger. Watch the voltage before, during and after when the charger comes on and goes off.
For example, battery bank with no consumers = 34.0
Voltage right before battery charger comes on 32.5
Voltage when the charger is running = 36.5
Voltage right before the charger turns off = 37.5
Voltage after the charger turns off = 34.5
Now you can compare these to what it should be. Your charger probably has an "on" voltage and an "off" voltage. If it's coming on and off at it's specified voltage, it's OK. If you don't know or can't find it's spec, it's probably something like that shown above, coming "on" at 32.0 to 33.0 and going "off" at 36.5 to 38.0. Chargers use voltage as a state of charge indicator, but it only works if the batteries are OK.

If the charger is doing its job but just cycling very fast, the problem is likely in the batteries. One or more could be shuphated up. To find out, get a good hydrometer and measure the specific gravity in every cell of every battery, after the charger has been off for 15 minutes or more (shut it down if necessary) and before you run any consumers. Get actual number readings for the cells.

Here's the real state of charge for any given cell, (for 80 degrees farenheit):
1265 = 100%
1250 = 85%
1200 = 55%
1150 = 20%
1100 = 0%

You can tell if the bank really has a full charge by whether all the cells are at 1265, assuming 80 degree temps. If so, you're 100% charged and no sulphation. A bank where most cells are at 1170 or so, is sulphated and would return a false high voltage (like 37.5V) when it is only 25% charged, causing your charger to shut off. Also, you can see if a cell has gone bad in one battery due to it's low reading compared to the other cells in that battery. This would cause the whole bank to not accept a full charge. As marine batteries get cycled, they slowly become sulphated and will return a false higher voltage without accepting a full charge. Then they need to be regenerated (equalized) by an intentional long charging cycle while monitoring the specific gravity of the cells until they are all brought up to around 1265 with no low cells.

As much of a hassle as this is, it can mean the difference between batteries that will run your refrigerator, lights, heads, etc. all night and all day, or a bank that runs low unexpectedly. If your charger has an equalization cycle available, it can be run without shutting off for long times without regard to voltage. Water your batteries up, run the charger full blast for hours and hours and check the cells as you're doing it. Make sure they have enough water and don't overheat as they're being equalized. When they ALL get up to 1265, you have equalized the bank, they'll hold a full charge and your charger will now go on and off normally.

If you can not get all cells up to 1265, you have a bad battery(s) which should be replaced.

Doug Shuman

[ritchievail]

My Findings—

I got home Friday and performed the initial test as suggested. I just turned over each engine to see which was giving trouble. It turns out that it is indeed the port side bank; all I got was a click, click, and click.

The fist thing I did was fill each battery with distilled water, each hole held from ½ to ¾ of a cup. The charger seemed to start running in a more normal fashion. I let it run a few hours and decided to let the batteries sit overnight with the charger off to see how long they are holding a charge. When I tried cranking again in the morning the port side had plenty of charge to crank the port side engine. The temperature of the block was roughly 40 degrees and the engine had not been started in over a month, not to bad!

While running my gauge showed that the port engine had a little less then a ~28V charge, starboard was not a lot better at ~31V. I let them run a while without much improvement. (The charger was still turned off) So I turned off both engines and turned the battery charger back on and let it run on auto all day. In the beginning the charger ran a good 30-45 minutes and resumed a more normal operation after the initial charge.

Sunday everything was back to normal. I checked the gauges from time to time as well as cranked both engines and both gauges read 36V. WOW, did filling the batteries really make that much of a difference? I plan to go through the exhaustive test sometime in the next few weeks to make sure everything is indeed back to normal.

[MikeP]

If the water level was below the top of the plates, then any amount of plate NOT in the water reduces batt capacity by whatever percentage was exposed to the air. Further, IF the plates were dry for very long, the portion that dried out is usually not recoverable. So the the battery capacity overall will never be better than the remaining good portion of the plates can supply. Perhaps the level was down sufficiently to reduce capacity but NOT long enough to damage that portion of the plates.

[ron6785]

While a 4 second on and off cycle is indicative of a problem. I have all AGM batteries and my 32 volt charger does come on frequently for just a second or two and shuts off. I was assured by the electrician that updated my system that this was normal. It seems to me that the charger shouldn't be that sensitive, but other mechanics have indicated that the charger should be set to keep the batteries topped off.