Battery Super Hot, May Not Be Taking a Clharge

[Gone2long]

Current problem is as follows:

I have a solar charging system on the boat. Have 2 engine batteries and two house batteries, all 4 batteries being large, 3 SMF, N70 Motolite auto batteries, the house batteries having been purchased in Sept of 2013.

When connected to our solar array, one of the house batteries becomes very, very hot -so hot, you cannot touch the terminals without getting a burned finger.

Consequently, I have disconnected that battery. The other batteries read OK, and the solar charger/power distributor seems to be working fine, so I figure that the "hot" battery is simply dysfunctional, and needs to be replaced. I disconnected it in the am and tested it using a multi-tester in the late afternoon. At that point, the battery read about 11.5 volts.

My take is the battery is shot, but I would like a second or third or many opinions. Also, if it is shot, should I replace the 2nd house battery as well, since it was bought on the same day, just about 3 years ago?

Please refer to my earlier thread "12 volt battery shows 15 volts" for further details on the system.

Thanks to all for your past advice and valuable support

Regards,

G2L

[denverd0n]

Yep. Classic symptoms of a bad battery. Good that you found it when you did. In that condition a battery can get so hot that it will literally explode.

[a64pilot]

Second opinion, it's shot.
If it's less than three years old, I'd try to figure out what the problem is
Yes conventional wisdom is replace all batteries in a bank together, however if money is a concern , I'd do a capacity check of the remaining battery and if it checks good, I'd likely just replace the one.
A "real" capacity check is I'm sure beyond your capabilities, however a pseudo one can be done with something as simple as a car head light, not real accurate but enough I believe to find a bad battery. I suspect your other battery is nearly shot too, and maybe your overcharging them?

[nigel1]

Normally I would have expected a battery with a dead cell to give a reading of 10.5V if it had recently been on charge. If you have access to a hydrometer, you could double check, measure the density of each cell, a dead cell will typically have a density of 0.05 less than a good cell, although your batteries may be so called maintenance free, and sealed, which precludes testing the density

In any case, if the battery is getting that hot, you did the right thing, get rid of it.
You said all your batteries are N70 Motolite's, these might be OK for starting an engine, but not much use for a house bank.
You would be better served replacing both house batteries with deep cycle batteries, if you have the space, 4 x 6V batteries in series/parallel would be a way to go.

[sailing_gal]

Definitely do a capacity check on the other batteries because one bad battery will damage the others. The Battery Warehouse near me will loan out capacity testers for free over the weekend---- you might try asking at one near you.

[hamburking]

I don't want to sound foolish...but did you check the water level in the battery? It may just have boiled dry. Adding distilled water up to the full mark might bring it back.

This is only for flooded, lead acid batteries. If yours are gel, agm, golf cart, etc, ignore this.

Whatever the cause, if it reads 11.5 under no load, its dead.

[travellerw]

Here is my guess.. Pulled from the following website..

Corrosion, Shedding and Internal Short - Battery University

“Soft shorts” are difficult to detect because the battery functions normally immediately after charge and everything seems fine. In essence, a charge wipes out all evidence of a soft short condition, except perhaps an elevated temperature that can be noticed when touching the battery housing. However, once rested for 6–12 hours, the battery begins to show anomalies such as a lower open-circuit voltage and reduced specific gravity. The measured capacity will also be low because self-discharge has consumed some of the stored energy. According to the 2010 BCI Failure Modes Study, shorted batteries accounted for 18 percent of battery failures, a drop from 31 percent five years earlier. Improved manufacturing methods may account for this reduction.

Another form of soft short is mossing. This occurs when the separators and plates are slightly misaligned as a result of poor manufacturing practices. This causes parts of the plates to become naked. Such exposure promotes the formation of conductive crystal moss around the edges, which leads to elevated self-discharge.

Lead drop is another cause of short in which chunks of lead break loose from the welded bars connecting the plates. Unlike a “soft” short that develops with wear-and-tear, a lead drop often occurs early in battery life due to a manufacturing defect. This induces a more serious short that is associated with a permanent voltage drop and could lead to a thermal runaway.

[bsurvey]

use a hydrometer to confirm it but it sounds like the plates are shot

[Terra Nova]

When one battery in an older bank fails, always replace the whole bank.

[TomLewis]

Umpteenth opinion, the battery is shot. Had this happen on an outbound in long island sound. Replaced the battery and all was well. Be careful with your solar panels. If your solar panels are good size and charge at a higher rate than the battery really needs (ie reading 15.4 or so), the battery will burn off excessive water as a reaction to the overcharging. I currently have that condition, so check the water often to keep topped off. Burnt up a couple of batteries over a couple of years before figuring out what was going on.

[Gone2long]

Originally Posted by a64pilot

Second opinion, it's shot.
If it's less than three years old, I'd try to figure out what the problem is
Yes conventional wisdom is replace all batteries in a bank together, however if money is a concern , I'd do a capacity check of the remaining battery and if it checks good, I'd likely just replace the one.
A "real" capacity check is I'm sure beyond your capabilities, however a pseudo one can be done with something as simple as a car head light, not real accurate but enough I believe to find a bad battery. I suspect your other battery is nearly shot too, and maybe your overcharging them?

Don't think over charging is an issue as the solar controller seems to be working fine.

Thanks for your note,

G2L

[Gone2long]

Originally Posted by nigel1

Normally I would have expected a battery with a dead cell to give a reading of 10.5V if it had recently been on charge. If you have access to a hydrometer, you could double check, measure the density of each cell, a dead cell will typically have a density of 0.05 less than a good cell, although your batteries may be so called maintenance free, and sealed, which precludes testing the density

In any case, if the battery is getting that hot, you did the right thing, get rid of it.
You said all your batteries are N70 Motolite's, these might be OK for starting an engine, but not much use for a house bank.
You would be better served replacing both house batteries with deep cycle batteries, if you have the space, 4 x 6V batteries in series/parallel would be a way to go.

Yes, I am considering going w. deep cycles on the two house batteries.
Got 485 watts of solar panels charging 280 amp hr worth of batteries, so
that, I am told is a good ratio. Comments?

Also, what is the cost difference on the deep cell v. motolite sealed batteries I now have?

Thanks for your input

G2L

[Gone2long]

Originally Posted by hamburking

I don't want to sound foolish...but did you check the water level in the battery? It may just have boiled dry. Adding distilled water up to the full mark might bring it back.

This is only for flooded, lead acid batteries. If yours are gel, agm, golf cart, etc, ignore this.

Whatever the cause, if it reads 11.5 under no load, its dead.

Thanks folks,

But, as noted above, the batteries are the sealed, automotive type.

G2L

[Gone2long]

Originally Posted by denverd0n

Yep. Classic symptoms of a bad battery. Good that you found it when you did. In that condition a battery can get so hot that it will literally explode.

Exactly what I was afraid of.
Thanx,
G2L

[nigel1]

Originally Posted by Gone2long

Yes, I am considering going w. deep cycles on the two house batteries.
Got 485 watts of solar panels charging 280 amp hr worth of batteries, so
that, I am told is a good ratio. Comments?

Also, what is the cost difference on the deep cell v. motolite sealed batteries I now have?

Thanks for your input

G2L

With that size of solar array, you need to have good charge controller.
In your other thread, you did not mention what type of charge controller you had. Without a controller, the batteries will certainly overcharge.

Cost of deep cycle batteries is not much different to automotive batteries, but I guess it depends on where you purchase.
Proper deep cycle batteries are normally 6V.
Some 12V batteries are labeled deep cycle, but a truer description would be Traction batteries.
When I looked at Motolite batteries I see they also produce traction batteries, the Solar Master range.