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Problem with new batteries keeping the charge

2K views 14 replies 8 participants last post by  chucklesR 
#1 ·
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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#2 ·
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.
 
#3 ·
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.

Bill
 
#4 ·
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%.
 
#5 ·
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.
 
#6 ·
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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#8 ·
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.
 
#7 · (Edited)
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.
 
#11 ·
Hellosailor: Thanks for info. I have checked the date on the batteries and it was 07/2013, so hopefully they did not have enough time to sulfate while sitting around. Also, the voltmeter is newly installed and calibrated (or at least that is what I was told). However, I will check on the maker's numbers for the voltage to see which apply to these batteries. I have double checked that nothing is connected, except for the bilge pump which is direct wired. However, I empty the bilge manually before leaving and check when I come back to see if there is any water to know whether it had a chance to cycle and thus draw anything on the battery.

svHyLyte: Good idea to check on the grounding foil. Will definitely follow up on that and check to make sure there are no leaks through the positive cables. Thanks.

Don0190: I do not believe that sg has been measured on the batteries. Will discuss this with the yard technician. Unfortunately, you are correct in assuming (as it is becoming more and more clear to me) that electrical part of the boat may not necessarily be their strongest area of expertise.

Once again, thank you to everyone who responded to my inquiry as it gives me a better idea as to which additional areas should be explored and addressed in trying to resolve this issue as well as educate myself better on the topic.
 
#12 ·
It may or may not have anything to so with your current problems (no pun intended), but a cycle counter (clicky-clicky) hooked up to the bilge pump circuit will let you know for sure just how much your pump is working. I put one in my boat and it has twice let me know of problems I otherwise probably wouldn't have caught.
 
#13 ·
dog-
I was told by a battery distributor that for wet cells, some companies actually fill with a different electrolyte (different sg) depending on the climate in the area they are sold to. So if you have "New England" batteries, or "Tropical" batteries, even allowing for temperature corrections there is apparently some difference in what the "right" sg should be, depending on how they were initially filled.

If you really want to keep tabs on the batteries, there are also electronic capacity testers now Amazon.com: battery capacity tester: Automotive
Some under $50 and that's a third option. If the tester agrees with the rating, you know they're probably just fine.

I just find anytime I mess with testing sg, there's a new hole burned through something shortly after. And if the electrolyte hasn't had time to equalize in the cell, which can take hours, then you need to suck it up, squirt it back, swirl it around...and let it stand to get the air bubbles out too. SG isn't a panacea either.
 
#14 ·
Depending on the capacity of the new house batteries and the capacity of your charger, there is a very good chance that 3 to 4 hours of charging is not bring the batteries to a 100% charge as several others here have noted. Does the charger indicate that the batteries are fully charged?
 
#15 ·
3-4 Hours is not enough for a full garunteed charge. You are only getting a flash charge. You'll need an overnight charge then 24 hours of sitting time to get a good state of charge reading.
Better yet - get a battery monitor like a Victron BMV 600s and hook it up. Simply using voltage readings for state of charge values is less than optimal.
 
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