I've had a similar experience w/ a battery that had been flat for about four to six years, although I didn't end up using one of those smart chargers, just a motorcycle tender. I tried taking it in to have an auto parts store charge it but the charging machine wouldn't do it and the sales person said it was dead. Took it home and connected it to a 2A/12V motorcycle charger for about six hours, let it rest for a day, then charged it for a full day and it showed the same voltage as my other good batteries for about a week, and has dropped a couple volts in the past week. I figure on letting it drop a bit more then taking it into the auto parts store so they can charge it w/ something more powerful to hopefully break up the rest of the deposits.

You mean the case bulging actually went down too?

omgwtf: I've read that's the prescribed means for trying to revive a totally flat battery - low charging current for a long time. May not cure hard sulphation, but it'll eventually turn the water back into sufuric acid.

There's a guy in Vancouver, BC who claims he can revive dead batts. He runs them in a converted EV pickup:

https://www2.blogger.com/profile/04941436561350451191

Last time I visited, he had blown up his controller though, and was off the road awaiting repairs.

As I understand it, the bulging is caused by sulfation - the crystals pushing outwards causing higher pressure inside the cells.

But yes, the bulging almost completely disappeared after a day :thumbup:

It's funny. I have the impression from the old hands on the EV List that desulfators are sort of the equivalent of acetone to the fuel economy crowd. Some people swear by it, many have tried it, some question the physics/chemistry behind the theory of operation, and nobody knows of any controlled studies that prove they work (at either prolonging the life of a healthy batt, or bringing them back from the dead to any usable degree).

Sulfation is a real thing. Like its been said above, some cars just don't charge the battery properly and end up doing harm. Also another killer is letting your car sit with the alarm set and various other computer bits draining power. When my daughter was in college her old camry sat for 3-4 days at a time then only make a short trip and repeat.... After I replaced the battery the third time I picked up one of those Volkswagen solar battery chargers on ebay and never had another problem.

You don't need a magic pulse desulfator though. A charger you can adjust the voltage up to about 15vdc will do. I have a very old analoug charger I use for this.

Heres a few links I have on Battery's, theres more than you want to know here:
https://www.e-marine-inc.com/articles..._charging.html
https://www.batterystuff.com/tutorial_battery.html
https://www.batteryfaq.org/

Roll your own desulfator:
https://www.shaka.com/~kalepa/desulf.htm

Interesting tidbit from the second link:

I have a battery charger that desulfates, along with 3 others that don't, along with a number of vehicles, and spare batterys that sit for months at a time, and at least on my motorcycle I end up having the battery last twice as long when I use the desulfater charger, I'm confident that the idea of desulfating is based off science, and I haven't yet heard anyone claming with any confidence that desulfating is bunk.

Some very experience solar electric (PV) dealer/installers swear by the desulfators. We have one on our house batteries, but of course will need another 15 or 20 years of use before we know if it may have made a difference. But I thought that spending about $100 on the desulfator was cheap compared to the $4000 cost of the batteries.

trebuchet03,

Does bulging also occur with batteries that have removable cell caps? Or is the bulging caused by the physical crystals pushing out instead of some sort of built up gas pressure inside the cells?