[T3] Cold Battery

[Jim Adney]

On 28 Jan 2016 at 1:49, J. Jonik wrote:

> 71 FI Standard sat for days under snow and started on first try.  But
> then, about 3 days later, still sitting...not having been driven
> yet...it almost started on first try...then didn't go...then got
> weaker and weaker, with just groans.  

All lead acid batteries have some "self discharge" that goes on 
continuously. Plus, on our cars, the clock may still be drawing 
current. Any car that's allowed to sit for a long time will end up 
with a dead battery. This can usually be recovered, but the longer 
it's been discharged, the slower the recharge should be.  

If it's been days, a quick charge for a couple hours will probably 
suffice. If it's been weeks, a slow overnight charge might do it. But 
if it's been months, plan on charging at a rate of 0.1 A or less for 
a week or so.

Trying to recharge faster will just damage the battery. As a test, 
measure the voltage on the battery as you're charging it. If that 
voltage is over 14.4 V, you're charging too fast.

Also, keep in mind that the acid in a fully charged battery will 
never freeze, but the acid in a discharged battery can freeze at 20 
F. Freezing is really, really bad for a battery, so you should do 
whatever you can to prevent that.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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