Can short circuited batteries be recovered?

[kflod]

Hi,I just installed a new bank with trojan t875 wet cells batteries.Some components in the autopilot must have been short circuited, because the pump went crazy and soon after (approx one minute) the brand new batteries were dead = only measuring 4 volts...I have now disconnected the AP components, but the first question one is: can i recovered the batteries? And if so - how? The batteries reached a temp of approx 100-110 fahrenheit before they died.Thanks Kristian

[Boatsb]

I'd be careful.

The batteries are not even close to chargeable at 4 volts. Assuming they were 8 volt batteries you may be able to put some electrons into them with another 8 volt battery but with such a variance they could cause a fire or explosion.

Unless you have special gear I dont see it being a good idea

[MVCaprice]

Toast. Literally.

[miboatnutz]

Something doesn't smell right here. Lol!

You may first want to try and better determine the failure mode for those batteries. Did they indeed short out or were they heavily discharged due to a load applied to the battery bank?

There's a difference.

If this was an OEM installed autopilot, I'd find it hard to believe that they didn't have adequate circuit protection in place to prevent a dead short going all the way back to the batteries (regardless of age). You didn't mention it but if this is indeed a Hatteras, they're some of the best engineered boats in the world so highly unlikely they'd lack appropriate breakers, fuses and/or thermal overloads to protect the main 32 volt system.

I'd suggest the following:

1. Disconnect all the batteries in the affected battery bank.
2. Measure voltage across the terminals on each battery. If you get a voltage reading other than zero then it's not likely a dead short in the battery.
3. If you do get a voltage reading, I'd take the batteries to a auto/truck battery store or wherever you bought them from and see if they can bring them back to full charge. As others have suggested, this would take specialized equipment.
4. ALTERNATIVELY you could try and bring them back to full charge yourself, but that would require a good 8 volt battery and an eight volt charger. Wouldn't suggest this step if you don't know what your doing because bad things could happen otherwise.

All that said, the batteries still may be toast, however since they're new, I'd at least make some further attempt at determining condition and possible restoration rather than just chucking them.

My 2 cents.

[kflod]

Thanks for the replies folks!I did the installation myself, but wiring and breakers are actually installed according to spec and best practices. I suspect either a 32-24 dc converter or a bad cell in one of batteries to be the culprit. Anyhow, new batteries are on their way, and will ship the toasted ones back to the dealer.One last question; is it normal for Hatteras (54my 1988) to have a 24V circuit as standard? The way the supply 24V in my boat's setup is to connect the positive terminal to battery no 3 in addition to the 32V supply for all four connected batteries. This would mean the the last battery would ideally need leveling at intervals, but I can't find any such equipment?ThanksKristian

[Boatsb]

Bad practice. Dont pull off any less than the full bank.

[kflod]

Bad practice. Dont pull off any less than the full bank.

Ok, so this is not original Hatteras wiring then, but rather something PO has done? Kristian

[miboatnutz]

What he says....... and that's correct as this would definitely not have been the way Hatteras wired it from the factory.

[kflod]

What he says....... and that's correct as this would definitely not have been the way Hatteras wired it from the factory.

Thanks, good to know 😊

[kflod]

Might have found the issue..?I think perhaps the Guest battery switch has short circuited. Could that happen? The cables that are now deattached from the port battery bank (pos and neg) has, according to my Fluke multimeter, connection. That shouldn't be, should it? While testing, the battery switches are off, both for the engine and ship's service. Also, as you can see from the attached picture, there is a connection between the breaker chassis (neg/earth right?) to each and every one of the cables inside. Again - should it be like this? I checked starboard breaker chassis, and it did NOT have any connection to any of the cables inside.Any advice greatly appreciated! Kristian