[LamerDeluxe (tm)]

I have two BP2ex batteries and one BP-100. All of them are dead, probably because they haven't been used for a long time.

These are lead-acid gell-cell batteries.

Now, I've read about reviving them by charging them with a 20 volts source. I've tried it and nothing happened. I think my amperage was too low.

Anybody here succesfully tried this before? What amperage is needed?

Here's a message about this I found on the internet:

>>>

In case someone else has the same problem..

PROBLEM: I had two sealed lead acid rechargeable batteries of my Sony D-25 CD player fully recharged, then left unused for some 6-8 months. When I tried to use my CD player again I noticed that the batteries seemed to be empty and could not be recharged with the CD player's built-in charger.
I noticed that the internal impedance of the batteries was several hundred Ohms and they didn't seem to hold any charge.

SOLUTION: I was told to recharge the batteries using a high voltage (like 20 volts/cell) and using a series resistor to limit the charging current in case the batteries became alive again. Someone also adviced me to recharge/discharge the batteries several times to bring them back to life.

This is exactly what I did with the first battery. I used 20Vdc with a 240 ohm resistor in series with the 4V battery. After some 20 hours of recharging and discharging the battery was almost like a new one (at the beginning the battery voltage raised to 19.5 volts but it came slowly down to 4-4.5 volts). I'm playing a CD with the 'dead' battery right now..

I'm currently recharging the other battery and I believe it will wake up as well. Thanks to all people who e-mailed to me!

 

[kevin gilmore]

With respect to the high voltage trick on lead-acid batteries
it only works if the battery is sulfated. (oxidized) If the battery
has even the slightest crack and the water has evaporated,
no amount of high voltage charging will bring the battery back.

Sometimes this trick works better on nicad batteries.

 

[LamerDeluxe (tm)]

Quote:

Originally posted by kevin gilmore With respect to the high voltage trick on lead-acid batteries it only works if the battery is sulfated. (oxidized) If the battery has even the slightest crack and the water has evaporated, no amount of high voltage charging will bring the battery back. Sometimes this trick works better on nicad batteries.

As these batteries are most probably dead because of lack of use, I guess there would be a good chance of reviving them.

Do you happen to know what kind of amperage would be needed?

 

[earthling]

Quote:

Originally posted by kevin gilmore With respect to the high voltage trick on lead-acid batteries it only works if the battery is sulfated. (oxidized) If the battery has even the slightest crack and the water has evaporated, no amount of high voltage charging will bring the battery back. Sometimes this trick works better on nicad batteries.

When we were racing 1/10th scale R/C you would discharge the battery after a race by strapping a huge resistor across the terminals (in parallel with a light so you could see it was discharged). If you left that on too long the batter would become over-discharged and would not take any new charge.

You could always tell when someone did this because you would see them race outside to zap them from the car battery. This was before someone came out with commercial, automated dischargers.