Thermal Runaway overheating batteries

[IanR]

After a very slightly bumpy ride up the Alderney race yesterday evening we arrived in Cherbourg and amongst other things out the shore charger on.

I woke up to feel the very warm floor boards over the battery bay and immediately vented and powered off. It seems I have cooked my new battery (1 month old) as my old one has shorted to 10volts and boiled. This is the second Varta Professional I have had do this in 5 months. Is this a common failure mode of these batteries (sealed lead acid)? Perhaps shaking it up did not help, but this is a sailing boat and it was relatively benign to be fair.

I have no battery temperature sensing which is something I will resolve on return home and the shore charger is a Sterling and was running intermittently with fan on last night which awoke me and my suspicions.

Thoughts from the panel gratefully received as this experiment could get expensive

 

[KellysEye]

Shaking or even corkscrewing (as we've done) sealed lead batteries shouldn't cause a problem, is the Sterling a smart charger? The charger could be the problem.

 

[pmagowan]

Certainly it seems odd and the batteries seem not to be the common factor since this is the second one. I would also suspect the charger. Get one with temperature monitoring.

 

[GHA]

Sorry, no specific answers but...

http://batteryuniversity.com/learn/article/corrosion_shedding_and_internal_short
Good website.

Also, a cheap panel voltmeter off eBay straight onto the battery terminals is a great addition, see exactly what's going on.

 

[IanR]

Sorry, no specific answers but...

http://batteryuniversity.com/learn/article/corrosion_shedding_and_internal_short
Good website.

Also, a cheap panel voltmeter off eBay straight onto the battery terminals is a great addition, see exactly what's going on.

Agreed both panel meters and DVM used to diagnose the fault, battery one is 10v offload only and new bat 2 is in load at 12.3v although one of the cells on the new battery feels warmer than the others on discharge , I have been sensitive about putting the new battery on charge and have been constantly checking it seems to go from absorption at 14.2v to maintenance on 13.5v.

I am keeping a close watch as this is now the "get you home" domestic.

The Sterling is not the new pro version it is a model 1230 assume about 10 years old . It now has a green charge led on

 

[pyrojames]

This can occur with batteries in parallel. If the old one shorts internally, the the new one tries to discharge through it. I have only had it occur in bigger banks, where several others tried to top up that failed one. I took the failed one out and charged, and ran the remaining ones normally without a problem.

 

[rogerthebodger]

This can occur with batteries in parallel. If the old one shorts internally, the the new one tries to discharge through it. I have only had it occur in bigger banks, where several others tried to top up that failed one. I took the failed one out and charged, and ran the remaining ones normally without a problem.

I have also had that as I have 2 banks of 6 batteries each. What I do is the monitor the voltage across each battery separately each month and then remove any that have a low battery voltage and check after the one is individually charges.

Also if you do bet a battery with one cell shorted internally you will also be overcharging the other 5 cells in the battery which will overheat and damage the remaining cells.

 

[Scomber]

We've put all new sealed lead batts in this yr- settings on our old sterling had to be set for the sealed type---- just a thought.

 

[savageseadog]

I think the OP has been very lucky. Could have been much much worse.

 

[Len Ingalls]

This can occur with batteries in parallel. If the old one shorts internally, the the new one tries to discharge through it. I have only had it occur in bigger banks, where several others tried to top up that failed one. I took the failed one out and charged, and ran the remaining ones normally without a problem.

Agree-this is likely what happened.
"Sealed" lead acid batteries are not sealed-they require at least a small vent hole per cell.
You may find pry out caps-sometimes hidden under a label,etc.
Recommend you check fluid levels in good bat. & top up as necessary.
Sounds like it was "boiled".

Hope this helps / Len

 

[halcyon]

After a very slightly bumpy ride up the Alderney race yesterday evening we arrived in Cherbourg and amongst other things out the shore charger on.

I woke up to feel the very warm floor boards over the battery bay and immediately vented and powered off. It seems I have cooked my new battery (1 month old) as my old one has shorted to 10volts and boiled. This is the second Varta Professional I have had do this in 5 months. Is this a common failure mode of these batteries (sealed lead acid)? Perhaps shaking it up did not help, but this is a sailing boat and it was relatively benign to be fair.

Long time ago we had the same problem with Sealine batteries, but intermittent. Turned out to be a bit of lead flash from welding intercell links in the battery, electrolyte moved with boat movement, bending the lead to form a link or beak the link. Resulting in a similar fault that you have, turned out to be a fault over many months of battery production.

Brian

 

[IanR]

Thanks for all the feedback, given that I have had two such events inside five months I am thinking of a strategic change, it's probably driven by paranoia but here goes

1. Separate paralleled batteries by relays
2. Trigger relays by battery voltage and temperature sensing
3. A gas detector

Control the whole lot to ensure that there is no fire risk

By the way the charger is behaving perfectly on only one battery and the battery is now properly charged on its own

It seems to me that if such overheating were regularly occurring then all systems would be set up this way so am I paranoid and if not are there any standard systems that do this or do I build it?

Cheers all, glad to have got back safely