Battery Problem

Shadowfax

Shadowfax

Member III
I have 3 Rolls group 27 batteries that I use as the house bank. The batteries are charged by a Xantrex “smart” charger and I have a Link 10 monitor. These batteries where fully charged and topped off in the fall when I put the boat away I’m still on the hard and have been charging the batteries when I’m down. . I have noticed that the charger seems to be constantly charging around 14 to 16 amps for hours and hours which I think is way too long at the rate of charge. After this charging and allowing the batteries to rest a bit I’m showing a charge via the Link 10 at 11.85 to 11.90, with no load. I would think that fully charged batteries would be showing closer to 13.

I’m beginning to think one of my batteries has a bad cell. The question is which one. The marina I’m at apparently doesn’t have a battery stress tester [or won’t lend it to me] and I really don’t feature taking the batteries out of the boat to find someone with one. I do have a hydrometer, the squeeze bulb type, and I’m wondering if this can spot the bad one with the three batteries wired together. My suspicion is not, as the bad battery is dragging the good batteries down. Would separating them make a difference?

I haven’t tried anything yet, but it looks like the snow is about to end and I’ll get down this weekend in upper 60’s weather to do what needs to be done. Any suggestions, comments, or abuse, would be welcomed.
 
Loren Beach

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Put the Squeeze on it

I once found a single bad cell in a car battery while it was still wired in. No wonder that battery would no long 'hold a charge." :boohoo:

Remember that your hydrometer just measures the specific gravity of the liquid in an individual cell. This should indeed tell you if you one bad or weak cell.

A resistance-based "tester" will usually test the reserve capacity of the whole battery, but that's not really what it appears that you need to know.. at least not just that piece of info alone.

That "mature technology" squeeze bulb dingus seems like just what you need for this bit of cell-level detective work.

Best,
Loren
 
H

Howard Keiper

Moderator
I think what I would do is to separate the batteries, and beg, borrow or steal a 'battery conductance tester'. This is the device that Rolls and other mfgrs use to determine the actual condition of a battery. Warranty decisions are made predicated on the outcome of the test, which takes all of 10 seconds or so and can be done without removing the battery. It's what the ABYC recommends as well. It may not be able to tell you if you've got a bad cell...or cells, but it will tell you whether your battery is good or bad, and if good, how much life you should expect from it.
Many so called 'load testers' put such a heavy load on a battery the test itself can finish off a marginal unit....maybe that's a good thing after all.
 
T

ted_reshetiloff

Contributing Partner
Paul not sure if you feel like driving to Annapolis but I have a load tester you can borrow if you want. The hydrometer test will most likely tell you what you need to know though. Try that first and if not sure then think about a drive to Annapolis....
 
R

rgoff

Member III
A fully charged battery (wet cell) is 12.7v after being off the charger for a while and with no load. Try disconnecting them and charging one at a time to see if it gets up to around 14v on the charger.
 
R

rwthomas1

Sustaining Partner
Separate the batteries electrically and leave them for a few hours so the surface charge stabilizes. Then test each cell with a hydrometer. This should indicate pretty quickly if you have one or more dead cells. Test the voltage too after letting them rest a while. I am betting on one dead battery. RT
 
Tom Metzger

Tom Metzger

Sustaining Partner
Options

I suspect that you are dealing with a shorted cell in one of the batteries. If you don't want to use a hydrometer there are other options.

Most likely just separating the batteries and letting them sit for a few minutes will probably allow you to pick the bad one with a voltmeter. It will have a lower voltage than the others.

If you have a DC clamp-on ammeter you will be able to tell which battery it is by measuring the current along the string of batteries while the charger is on. Only one of the batteries (I hope) will be taking the majority of the current.

Lacking the DC clamp-on ammeter you can isolate one battery at a time to see what happens to the total current. Do this by taking off the leads from one battery and connecting the leads together off of the battery post. Just do this on one post, positive or negative, for each battery.

After isolating the bad battery it will take a while to bring back the others as they have been low for quite a while.
 
Shadowfax

Shadowfax

Member III
Just a follow up.

I took the batteries out of the boat and to the local Rolls battery guy. He put a test on them and said they were not worth the time it would take to put them back in the boat. No bad cell in one of the batteries, I needed three new batteries. After a Q & A session it was determined that my batteries where bought in the spring of 01, meaning these batteries had six years of service on them. The battery guy pointed out that these particular group 27 only had a one year replacement and three year prorated replacement warranty, so they didn't owe me anything. I think this was to make me feel better. Of course Rolls doesn't make that battery anymore, so I'm looking at three new batteries with 22 AH [ea] less then the one it replaces, however the battery is 10 lbs. heavier then the old one and has a two year replacement and seven year prorated warranty.

They make a group 30 with the same warranty and I would have only loss 4 AH ea., weighed an additional 10 lbs. over the ones I bought, but the cost was $100 more per battery. I was/am a little concerned about the loss of amp hours, so the battery guy offered to give me full credit for the 27's towards the 30's if I wasn't satisfied with the staying power of the 27's. That sealed the deal. I installed the batteries and all [except my wallet] is well.
 
V

valentor

Member II
Paul;

The overall life of your batteries raises a bit of concern. There may be some issues with the way you are using them and possibly with your charging system.

In general, batteries should only be discharged to about 50% of their rated capacity, then they should be recharged to more than 90% before they are deeply discharged again. Discharging them to well below 50% dramatically shortens their life. Many batteries can only stand 20 or so such deep discharges before a few cells die and become resistors which render the entire battery unchargable.

The previous owner of my boat replaced one of the batteries every year, but also it was necessary to run the engine about every 4 hours or so to keep the lights bright and the instruments functioning at night.

After completely replacing all the wires (significantly increasing their size), alternator, regulator, installing a battery monitor and upgrading to AGM batteries in 2001, the batteries still test to 99% capacity and can power the onboard systems for several days without a recharge - as long as I run the engine while running the microwave ;)

Check out your charging system to be sure that it is restoring ample amounts of charge and monitor your voltage so that you don't draw below 50% of the rated range and you should see a significant improvement with your new cells.

There are many threads on battery systems on this site.

Good Sailing;

-Steve Valentor
 
Shadowfax

Shadowfax

Member III
Steve,

I have upgraded the wiring from what Ericson installed as per Tom Metzger's recommendations which are archived here and I heartily recommend. I have a 3 stage Xantrex charger with a the Xantrex battery monitor and a Link 10 system monitor. I have a Balmar 100 amp alternator with their smart regulator. The batteries that I replaced had 6 years of service on them and according to Rolls designed to last 3 years. As much as it pained me to spend $500 on new batteries, I had to agree with the Rolls guy that they really didn't owe me anything. The new ones are designed for 7 years of service and the Rolls guy says he thinks I'll get 10 out of them if the other ones lasted for 6.
 
Shadowfax

Shadowfax

Member III
Howard,

They threw a quick charge on them and then did a stress test. One of the batteries had 2 bad cells. The other 2 still had life but the Rolls guy said they weren't worth the time it would take to put them back in the boat. He recommended that you replace all of the batteries in a bank at the same time because the failing battery or batteries will drag down the new battery and shorten it's life, hence I replaced all 3.
 
You must log in or register to reply here.
Top