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post #1 of 15 Old 10-14-2013 Thread Starter
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Problem with new batteries keeping the charge

Recently had two new house batteries installed by the yard as part of bigger maintenance project. Engine battery is a relatively new one (about a year old). All batteries are wet-cell. In the process, also changed my old switches from "ALL/1/2/OFF" to just "ON/OFF."

Nonetheless, it seems that the new system is not keeping the charge. I will leave the batteries fully charged by running a charger (shore plugged in) for at least 3-4 hours without any load on the batteries. All three batteries will show a charge of 13.2-13.4V upon completing the charge and then slowly settle to around 12.8V. When leaving the boat for the week, I usually turn off all the switches at the [breaker] panel as well as turning both battery switches to "OFF" position. (The bilge pump is wired directly.) I will also empty the bilge with the hand-held bilge pump.

However, when I come back to the boat a week later, I usually find both of my house batteries down to 12.5V and the engine battery around 12.6V. The bilge is still empty and nothing else is on. I have observed this on several consecutive weeks and it is driving me crazy. The yard mechanic appears to be stumped as well.

Any suggestions ? Thanks in advance.

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post #2 of 15 Old 10-14-2013
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Re: Problem with new batteries keeping the charge

Even good wet-cell batteries will self discharge about 5-10%/month. Once you've completely charged you batteries, and they have "rested" for a few hours, their no-load voltage will be about 12.6V in a nice cool bilge. After a week or so that could easily dip down to 12.5V on you meter just from self discharge. If you want to keep them topped off, without leaving the boat plugged in, get a 20W solar panel and a charge controller.

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post #3 of 15 Old 10-14-2013
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Re: Problem with new batteries keeping the charge

New batteries need to be "exercised" a few times before they behave as you'd expect. They need to be discharged to about half capacity, then FULLY recharged. This takes more than 3-4 hours, no matter the size of your charger.

The comment above re: self-discharge is correct. And, solar panel(s) for maintaining a full charge is a good idea, too, since if resting voltage falls below about 13.4-13.6vdc sulfation rates increase, shortening battery life.

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post #4 of 15 Old 10-15-2013 Thread Starter
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Re: Problem with new batteries keeping the charge

Thanks for the comments and input.

I did expect some discharge over a month or so. But what I am seeing is 10-15% discharge over a week.

Also, since the batteries were installed in August, I have anchored overnight several times and had the batteries go down to 12.2V or so before fully recharging them back to 100%.

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post #5 of 15 Old 10-15-2013
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Re: Problem with new batteries keeping the charge

Dog, are you absolutely, positively, checked-it-with-my-own-hands-and-eyes certain that when you leave the boat for a week, nothing is connected to the batteries? No bilge pump, no nothing?

Brand new batteries typically are rated at 12.6-12.7 volts, you would need to check with the maker to find out what the right number is for yours. And then check the date code on the batteries, it is usually stamped or embossed near the top, cleverly hidden under a label on the side. Batteries should not sit on the shelf too long before purchase, so if you bought them in August, a June/July manufacturing date is about as old as you should see. If they sat around, they probably also sulfated and wouldn't see 100% charge again.

So there's the voltage they were designed for, and a question of whether they were sitting, and then once you shut down and leave the boat it can easily take 24 hours for the float charge to dissipate then the electrolyte to equalize, and the "true" charge to show. On top of all that, you need to check your voltmeter, if it is not calibrated it can easily be off by one or two tenths of a volt on a 20 volt scale.

Check your numbers, check your measurements, odds are they are not discharging as much as you think. If everything double-checks and they really are discharging that much, you'd have a battery problem. Odds are, it is a "measurement" problem.
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post #6 of 15 Old 10-15-2013
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Re: Problem with new batteries keeping the charge

Dog--

In comparison with your experience, this past July 23rd I installed 4 T-105 batteries as replacements for our then 7 year old batteries. Trojan indicates the battery self-discharge rate of their batteries at about 4% per month and, with all the electrical services shut off, that is about what we have observed.

Also, while some have suggested that flooded cell batteries need to be "exercised" a few times to achieve full capacity, when questioned about this, the Trojan tech's indicated that it was really not necessary, at least with their batteries.

Given the foregoing, you may have a drain you are not aware of. Several years ago we had a situation where a grounding foil has chafed through one of the positive cables in a spot under and behind our engine and only discovered by accident. Once the cable was replaced (and armored) our mysterious discharge problem was solved.

FWIW...
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post #7 of 15 Old 10-15-2013
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Re: Problem with new batteries keeping the charge

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Originally Posted by Dog8It View Post
All three batteries will show a charge of 13.2-13.4V upon completing the charge and then slowly settle to around 12.8V.

However, when I come back to the boat a week later, I usually find both of my house batteries down to 12.5V and the engine battery around 12.6V.
These are wet cell batteries correct (asking even though you said they were)

Are you are going only by the voltages? I don't think your batteries are fully charged at all based on what you say. I bet they are only around 80% charged.

Have you measured the specific gravity of the batteries?

You need to measure the sg and charge till they are truly fully charged and only accepting around 2% of amp-hour rating as amps into the batteries at a voltage of 14.2-14.6V. Then you need to check the sg to see if they really are charged.

After you get there you should discharge them to 50% and then do it again and if your charger has an equalize function you should run it after they are charged.

BTW - it doesn't sound your yard guys know much if they have not told you this.

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Last edited by Don0190; 10-16-2013 at 07:04 AM.
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post #8 of 15 Old 10-15-2013
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Re: Problem with new batteries keeping the charge

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Also, while some have suggested that flooded cell batteries need to be "exercised" a few times to achieve full capacity, when questioned about this, the Trojan tech's indicated that it was really not necessary, at least with their batteries.

Well that is interesting as I've seen graphs on the Trojan site that indicate that their batteries need around 50 cycles before they start achieving their amp-hour rating.

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post #9 of 15 Old 10-15-2013
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Re: Problem with new batteries keeping the charge

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Well that is interesting as I've seen graphs on the Trojan site that indicate that their batteries need around 50 cycles before they start achieving their amp-hour rating.
Don--

So that there is no confusion, I know very little about electrics and so rely upon the experts, including, in particular, Bill Trayfors who posted above and has helped me on many occasions as has the poster Maine Sail. Having heard that cycling was necessary, after spending rather a good deal on the new batteries, to ensure I managed them properly, I phoned Trojan's customer service/technical assistance line and asked the technician I spoke with about the matter specifically. I merely repeated his comments herein above.

FWIW...

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Re: Problem with new batteries keeping the charge

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I phoned Trojan's customer service/technical assistance line and asked the technician I spoke with about the matter specifically. I merely repeated his comments herein above.

FWIW...
I never said that you were trying to mislead. I'm just saying that whoever you spoke to doesn't seem to be saying what Trojan says in their info.

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