Re: [T3] Renewing a dead battery

["Jim Adney" <jadney@vwtype3.org>]

On 13 Aug 00, at 21:52, shackedup wrote:

> Is there any way to 'refresh' an older battery that doesn't want to hold a
> charge any more?  I'm tired of buying a battery every few years.

If the battery just sits a lot and the car seldom gets used, then it 
can slowly discharge and go thru a process called "sulfation".

In the normal charging cycle, lead turns into lead sulfate as the 
battery discharges, but if a discharged battery is allowed to sit for a 
long time the lead sulfate changes crystal structure into a form that 
is much less soluble. In this state it is difficult to charge the 
battery, but it CAN be done if you are patient.

Sulfated batteries can be completely recovered by long SLOW 
charging. Use a good charger set on its lowest setting for a week 
or two. If you have a meter, the charging current should be 50-
100mA. Lower is okay, but more will just HURT the battery.

Note that there is NO way to recover a sulfated battery quickly.

I have also known people who left a car stored over the winter with 
a charger connected to a light timer. Set the timer to run the 
charger for an hour every day and the battery will never have a 
chance to discharge and sulfate.

Of course there are other things that can go wrong with a battery, 
and the solution above won't do anything for them.

-
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054

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