[T3] Battery

[Jim Adney]

On 22 Sep 2020 at 14:16, Gary Forsmo wrote:

> My Group 42, 12VDC '69 Squreback battery has been "at rest" in our
> unheated  (but attached) garage for 27 months. (The garage has 3 walls
> that are insulated, but NOT exposed to the outside elements.) I
> connected my Fluke Multimeter to to the battery posts and it read
> 12.40 VDC. That seemed surprisingly "high", to me.  What do you think? 

It probably doesn't have much oomph at this point, in spite of the rather 
normal voltage. All batteries undergo some rate of self discharge and 
lead-acid batteries develop lead sulfate on one their plates as they 
discharge. Over time, the lead sulfate recrystalizes and becomes much less 
soluble, making recharge difficult, because the sulfate ions will only go back 
into solution slowly. This is a sulfated battery.

Sulfated batteries can often be saved, but not if you're in a hurry. You need 
to apply a charging voltage that's higher than the battery's self voltage to 
reverse the discharge process, but you must not use voltages higher than 
what would electrolyze the water in the battery. What this amounts to, is 
something like 14 V and 50 mA for a week or two.

> 1.)  When the car is in the condo garage for the winter, is it OK to leave
> the battery connected to the car cables?

It's okay, but you should disconnect the clock, so the clock current doesn't 
run the battery down. Disconnecting one battery cable is equally effective.

> 2.)  Should I disconnect the battery cables and connect the "trickle"
> charger to the "in-place" battery until next spring?

That will work nicely. It's useful to put the charger on a light timer, so it 
doesn't run all the time. That prevents overcharging.

I have a couple Harbor Freight battery "maintainers" which seem to be 
effective plus they are cheap and often on sale. There's not any real 
difference between these "maintainers" and a trickle charger. There are 
probably intelligent Maintainers out there that actually do their job 
intelligently, but they are bound to be expensive.

> 3.)  Can the Square be driven 4 miles ("push-to-start") WITHOUT any battery
> in place & unconnected, at all?

NO!


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