Any tricks to bring back a dead battery? (12v)

You can try to "desulfate" the plates. It can work if the battery isn't too far gone. A BatteryMINDer® Plus 12 Volt 1.33 Amp Charger-Maintainer-Conditioner (Desulfator) | All | Battery Chargers by BatteryMINDers.com for about $60 will recover some of them.

JeffD

 

I heard that sometimes people use welding machines to ”kick start” batteries to life.

Basically this means, that welding machine does not have any electronics for safe loading of the battery. So welding machine just push high current thru the battery and sometimes battery chemistry come enough live to charged with regular battery loader. But don’t do this if you are not familiar with battery hazards.

 

Make sure to wear protective gear in case the battery explodes. (It can and does sometimes happen)

Better yet, turn the battery in for recycling and buy a new one.

 

That sounds soo dangerous!

 

Years ago, a guy I worked with swore by dropping an aspirin down in each cell of the battery.
I tried it once, and it didn't work for me.

 

Yep, I know.. But there is people who do it... I found this by Google:
Revive Nicad Batteries by Zapping with a Welder

 

the desulfator is your best option for lead -acid. this works well for batteries that have lost capacity due to sitting too much. for any EV'er who is running lead-acid (most of us in the NEV crowd are except for rich peole like daniel who can afford to dump 10,000 into Li batt pack) its pretty common knowledge that this can help add a bit of life to older batts.

 

That’s a completely different battery chemistry and in no way applicable to lead acid batteries.

NiCad (and NiMH) cells sometimes go short circuit, particularly when over discharged, due to crystal growth puncturing the cell barrier. Sometimes a brief but large charging pulse will clear the short, the so call “zapping” the cell back to life. (Dont use a welder that sounds dangerous, I just used a battery charger that's well over-rated for the battery being zapped).

Yeah it works, yeah I’ve done it several times, but generally the results are pretty poor and the cell is usually never the same. Typically a revived cell will have high self discharge and short lifetime before it goes short again.

Just take your old lead acid batteries in for recycling, it’s the best thing for them!

 

Ditto!

 

Yup, don't "bring" them back, take them back to the recyclers. They are chemically irreversibly damaged. Anyone who tells you otherwise should be avoided. LISTEN TO YOUR MOTHER! Those are the people she was warning you about!