Bad Battery Problem

[Joyce]

My boat is 18 months old. It has two 8D batteries installed by the dealer.
In August, I checked the levels of both batteries and topped them off.
I've been away from the boat since then, and it has been on shore power
with the xantrex charger on to keep the batteries properly charged.

I just got back to the boat, and going through my check-off procedures,
I saw that one of the batteries was very dry, with the tops of the plates
showing in all the cells. The other battery was just as I left it.

I refilled the low battery with distilled water last night and let it charge
with the xantrex charger, as usual.
This morning I opened the boat to the unmistakable smell of acid.
The battery that I refilled was very hot, and vapors were coming out the
vent caps.

I've disconnected the battery cables from this battery and I'm letting it cool.
I assume the battery's a goner, and I'll have to replace it. How I'm going to
move that beast is a mystery, but that's another story.

I don't know why this would happen to just one battery. Any ideas?

 

[Chuckbear]

Joyce, Defective battery, bad cables, loose or corroded connection, wiring issues, failure in the battery charger. Chuck

 

[Joyce]

Chuck ...

Charger's ok, it's charging the other battery fine.
Wiring's ok, I checked it.
Connections are perfectly clean and very tight.
I guess that leaves a defective battery as the culprit.
That was my thinking.

Thanks

Joyce, Defective battery, bad cables, loose or corroded connection, wiring issues, failure in the battery charger. Chuck

 

[dserrell]

1

 

[sailingdog]

I'd point out that you may have voided your warranty, by letting the plates go dry. This will ruin the plates and may cause the exact problems you've since experienced with them. Negligence, like not properly monitoring the battery's water level, usually voids the warranty.

 

[Stu Jackson]

They call them 8Ds because it takes 8 Darned big guys to move them!!!

Why replace the monster?

Get your warranty $$ back and do this: The solution is to replace that monster with (2) 6V golf cart batteries wired in series for 12 V.

If you run your boat with two separate house banks, then you're not combining old and new.

Downside is that eventually you'll want a bigger house bank and a separate reserve bank, so you'd have to combine the remaining 8D with the golf carts and could do that now. Since they're only a year old it's doable, but most people will say never mix old and new batteries.

You could deep six the remaining 8D monster and go with four 6 V golf carts, too.

Lotsa options.

Your boat, your choice.

 

[dserrell]

FYI we purchased a new battery direct from Interstate Batteries. Is was a blimished battery meaning the case had a very minor defect. We had asked the dealer to let us know when one was available. In less than a week we were able to purchase a new, with full factory warranty, Interstate Mega-Tron GRP24 12V Deep Cycle marine battery CCA550 RC140 @25A for $40. Retail for the battery was approximately $75. So if you decide to purchase a new battery or change your battery configuration and purchace new batteries, call around and you may find a significant cost savings. The Interstate Mega-Tron Deep Cycle marine battery we have is serving our needs very well! Good luck!

David

 

[Thread]

8D

We replaced our two wet cell 8D (eight dudes) batteries with new Interstate brand (30% discount because of buying direct) 8Ds in 2004. I keep them on a two month top off schedule, which has worked for us. We also keep them charged with an Xantrex charging system. Never had a problem and have yet to indicate the need to equalize them. Very happy with their performance. Should be good for another year or three.

Could be a defective battery, but it sounds as though you need to keep the top off schedule to no more than two months. Interstate will likely do a warranty replacement for you.

Thread

 

[Stu Jackson]

Another thoguht

You earlier discussed: Defective battery, bad cables, loose or corroded connection, wiring issues, failure in the battery charger...

Don't be so quick to dismiss battery charger as the culprit.

Given your two batteries, may I assume you have two separate banks? If so, then you are using the two separate outputs from the charger. It could very well be that be one output is not working properly and the other is. Just because one battery is OK, doesn't necessarily automatically follow that the charger is operating OK. I recommend that you measure the charger output voltages during bulk, absorption and float at BOTH charger outputs to confirm proper operation. If you just assume it's OK, you could well fry a new battery right off the bat (npi ).

 

[Fairwind]

If ONE of the batteries in a parallel connected bank loses a cell and and its voltage drops, the charger thinks it's discharged and try's to charge it at a high rate, boiling the fluid out of it and destroying the already junk battery. Also, the good battery will discharge into the bad battery, so yours must not have been connected together. When left unattended, I would turn off the main charger and instead just leave a small trickle charger connected, which can't boil all the fluid out or overheat the battery. You are lucky your boat was not set afire by the cascading malfunctions..

 

[seadaddler]

Warranty

I had the same thing happen to my 2 -4 D batteries and so went to interstate and almost got both replaced but the manager came back from lunch and said no just the one bad one.
Anyway I added them together one big bank and mine was just one year old and they been doing just fine,just check them often and keep fluid level over plates.
Nick

 

[Joyce]

More battery details

My two 8D batteries are connected in parallel, and make the house bank.
So they were both being charged from the same circuit on the xantrex 25
charger, with temperature compensation included.

I was away from the boat since August, and the boat was not used at all.
There were no electrical devices active and all of the DC panel switches were off.
So the only possible draw on the batteries would be if the bilge pump cycled.
And the bilge was fine.
So it was pretty much battery heaven. No drain and proper charging (I did
check the output of the charger).

Being away from the boat, there was no way to check fluid levels.
But for a basically-unused battery to dry out and fizzle out like this in three months?

 

[Fairwind]

As long as you are around and keeping an eye on your batteries, problems can be spotted quickly..But when left unattended for months, serious, expensive problems can develop..

I live in an off-grid, solar powered home so I'm very familiar with batteries and their problems. They are the weak link in this type of living..

 

[Douglast]

seems like overcharging...but the other one should have been in the same situation...strange...one thing for certain,a good battery charger is a must,,,and a good maintenance charger....and since you are using batteries that can be filled(maintenance style) its a good idea to keep a bottle of aspirin...in an emergency with a dead battery throw an aspirin or two in each cell and the reaction will give you a good chance at getting your engine started as the acid in the aspirin interacts with the battery acid and creates a strong surface charge....we always used 8d batterys in trucks and always found that four 6 volt batterys were much stronger the the two 8ds..

 

[Fairwind]

The most VALUE for your money with deep-cycle batteries are the 6V golf cart batteries.

Joyce, one of your 8-D's lost a cell, usually a shorted plate separator. It now becomes a 10 volt battery and the charger tries to make it a 12 volt battery. You see the results.

Trojan batteries are favored by the off-grid community..

 

[walt]

It seems the discussion is about two batteries connected in parallel (always) and one battery uses a lot more water than the other.

I have the same problem. Last time I checked the battery fluid, one battery took about 1/2 gallon and the other took no water. I think once this happens, the batteries are no longer balanced and there may not be much that can be done.. It seems that if you parallel batteries, you need to check water more often (or go with AGM's).

I find it hard to believe this could have caused the problem but after having my problem, I also re-wired my batteries. I initially had the wiring as shown on the left and I changed the wiring to what is shown on the right. It’s a small change but it "balances" the parasitic voltage drops in the wires caused by their resistance and the current flowing through them. In my case, the difference in battery voltage for the unbalanced case was likely less than 5 mv.

I think the batteries are trashed now and am thinking about going to two six volt batteries in series because I’m just not going to be that good about regularly checking the fluid level. So I probably wont find out if this made any difference. Could also be simply that the batteires I thought were identical - were not so identical even when new and with the same date code.

 

[Witzend]

Interesting evaluation Walt, but I'm having the opposite battery use the water in my parallel setup. I'm thinking the E difference you outline is insignificant to create an imbalance that would account for significant electrolysis to convert that much H2O. My thinking is that as the plates begin to sulfate the voltage drops, then the charger is constantly putting current into the battery with the degraded cell that won't completely charge. It boils down to where the current is going, no pun intended!

 

[Fairwind]

People who maintain battery banks fight this all the time. No two batteries are exactly the same. If you connect two "identical" batteries in parallel, one of them will have slightly more internal cell resistance than the other, so one always is fed more currant. Usually, one reaches full charge first, it's voltage climbs higher than the other battery and the weaker battery then takes the heavier charging current and they equalize and the charger shuts off. But if one has a bad cell, it never reaches float voltage and the charger keeps charging it until it boils out all the water from the bad battery..

Connecting a new battery with an older battery is another recipe for disaster. They are mis-matched and will "work" each other to death and will not charge properly..

 

[walt]

I would agree that it’s probably not the wiring causing this - Witzend having the opposite battery in a similar config have the water loss is interesting.

Why the advice not to mix different sizes of lead acid batteries in parallel - dont know. But once one battery starts to loose water (electrolyte), it "becomes" a different size battery - less plate surface in the electrolyte. Seems that this might be somewhat of a positive feedback effect. Once one battery looses a little more water than the other, the rate of imbalance increases causing even more loss.

Looks like I’m going to replace my 12 volt batteries in parallel with two six volt batteries in series. The main reason I’m doing this is that if the above is true, I won’t have to deal with water loss as much - possibly my poor maintinence "mode of operation" wont matter so much. Also, adding water with impurities increases self discharge in batteries and also shortens the life. So having to add water more often (even distilled water) could also shorten the battery life??

But then, a cell going bad on one of the 12 volt batteries doesn’t take your bank out - just reduces its capacity. Not so true for the two 6 volt batteries.. But.. that is what Ill have next time.

 

[Witzend]

I though about doing just that, for not only the imbalance problems, but a smaller form factor, easier on the back when replacing, but you are correct, a bad cell in that config could bring you down. Trade-offs Trade-offs.