Battery salvage

[Nick.K]

We have recently salvaged a 40ft sail yacht for parts, the hull was underwater for about 6 days. Inside were two 12v large deep cycle lead/acid batteries (non gel). Can these be resuscitated?

[PAR]

Not very likely, being shorted out for a week.

[gonzo]

If they were charged, the positive terminal probably corroded off.

[Nick.K]

Thanks for the replies.
I was wondering if anyone had actually tried to do it and if there were any issues such as changing acid etc. In the fishing community here, small boat sinkages are not uncommon and a few of the fishermen commented that the batteries would probably be useable. They are of a deep cycle type where the plates are probably strong enough to withstand being flat for a week.

[CDK]

If the terminals are still useable and no seawater has entered the batteries, try charging them with a small charger (approx. 4 amps) for a week and after that measure the voltage. When the reading is approx. 13 V connect a halogen headlamp and measure the voltage from time to time until the reading is 11 V. The lamp draws 5 amps, so if the voltage dropped to 11 V after 10 hours, the battery capacity is 10.5= 50 Ah.

If seawater did enter, the batteries are poisoned and beyond recovery.

[murdomack]

If you already have a battery charger, you have nothing to lose by trying CDK's procedure. Best of luck.

[murdomack]

Originally Posted by CDK

the battery capacity is 10.5= 50 Ah.

I was scratching my head there for a bit. Did you mean 10 X 5 ?

[mcollins07]

I have poured the acid out of batteries, refilled with new acid and then recharged them, to successfully bring them back to life. I think it is a long shot, but it does work occasionally.

[Nick.K]

Yes, it´s true, nothing to lose. I already have one on low charge and I'll try CDK's method of amp hours trial...though like murdomack I'm scratching my head too..

[Yobarnacle]

Sulphated batteries can be rejuvenated if the sulphation hasn't separated from the plates. Add a solution of epsom salt in heated water, several tablespoon fulls of liquid per cell. Agitate battery while charging. Glue a velcro sandpaper to the battery to attach an orbital sander. Set battery on old bed springs or shockcord web. Sander agitates very well, and pulls loose from the sandpaper afterward. The sandpaper can stay on battery case.

[Frosty]

In the old days !!!!! when batts were made of stouter stuff we as apprentices could not afford batteris so we would get a half decent one turn it upside down and hose it out getting settled muck from the bottom that could short the plates out. May times you could get a real good batt but it was only 9.5 volt due to the above.

A refil and a charge up got us up and running, kinda not very good but they worked.

[CDK]

Originally Posted by murdomack

I was scratching my head there for a bit. Did you mean 10 X 5 ?

Sorry for the confusion but I'm glad you understood anyhow.

[pistnbroke]

True frosty but they dont have a sediment space any more ..they moved the plates down to the bottom of the case and put more acid in then sealed the thing ..so you dont need to top it up because its got 4 years of electrolyte in there ,,,,,thats progress I dont think .

[Yobarnacle]

So did your efforts save the batteries? It's been 2 weeks since your post

[Nick.K]

No! Tried charging both, a complete waste of time. One took a small ammount of charging current but must have been shorting out inside.
We did manage to salvage practically every other piece of non electrical equipment including the engine which runs fine despite being underwater for six days (needs alternator and starter). The hull was a write off.