[T3] Re/ Endless Problems etc etc etc

Dave Hall dave at hallvw.clara.co.uk
Fri Dec 10 04:05:39 PST 2010

That's 12.90V with the charger off, I assume?   That's fine.   When charge
is being put into the battery, the charger has to push harder, and so it is
designed to work at more than the 12V to 13V the battery produces when
charged.   It doesn't have to push as hard to get 2 Amps flowing into the
battery - you've probably only got 1/2 Amp or less flowing in now, assuming
you are on the 2 Amp range.

A 12V lead-acid battery has 6 cells, each nominally 2V, which makes 12V.
When fully charged, each cell is actually about 2.2V, making 13.2V with no
load, while fully-discharged cells are around 1.8V, making 10.8V altogether.
That's similar to 5 fully charged cells and a short-circuited one, which is
the only situation that a shorted cell could be hidden.  Once the fully
charged good cells lose a bit of the 'top', they come down to 2V and the
battery volts (from 5 good cells) would be around 10V, which would show a

Don't get too concerned about voltages when charging, as they vary depending
on the battery charge state.  See what the voltage is when settled and in
use, but before the charging problems you seem to be suffering drop the
battery state to discharged.  Most of the time the voltage will be close to
12V, except for the fully-charged and fully-discharged states.

UK VW Type 3&4 Club

-----Original Message-----
From: type3-bounces at lists.berkeley.edu
[mailto:type3-bounces at lists.berkeley.edu] On Behalf Of J. Jonik
Sent: 10 December 2010 08:56
To: Type 3
Subject: [T3] Re/ Endless Problems etc etc etc

Advice was to put battery charger on low...2 amps...instead of 10 amps, to
get it up to  over 14.00 volts, or to 14.50,  to solve fuel injection
performance problems.

 Hours ago, when battery was Almost There,  at 13.90 volts (after a day of
charging at 10 amps) I turned it down to 2 amps for slower charge to go the
rest of the way.

 Now, hours later, the battery has lost an entire volt.  It's back to about
12.90 volts.

 How did battery LOSE voltage while on the charger?

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