[T3] Battery Issues

[Jim Adney]

On 25 Jan 2011 at 12:51, Chris Sheridan wrote:

> Seems like a go through a battery at least once a year in my 1970 automatic
> fastback. I usually just pick one up for about $90 at the local FLAPS  - my
> only requirements are that it fits under the seat and has top posts. I
> suppose I should be looking for other qualitys.

Our 12 V batteries are Group 42, which is what all 12 V VWs have used, except 
for the diesels. You should be able to pick any Group 42 battery and it will 
fit and last at least 3 years. I've never had one that lasted less than 5 
years.

[Our 6 V cars use Group 19L batteries. These are getting hard to find.]

To get that kind of lifetime, it's important to get the right size (Group 42 or 
Group 19L) and to install the battery clamps correctly. NEVER pound the clamps 
down on the posts; spread the clamps with 2 screwdrivers, slip the clamp all 
the way down on the post, and snug up the pinch bolt.

> I recently got a no start condition. Starter would not whirr merrily over
> with a screwdriver shorting across the posts. upon turn of key, solenoid and
> fuel pump can be heard doing their thing, but no starter. When I put the
> battery on my charger it reads fully charged 14 volts. when I start the car
> with the battery in situ and the voltometer hooked up, the volts drop from
> 14v to 2.5 volts. When I hooked up jumpers from another car that is running,
> the voltage drops from 14 to 3 and the starter never turns over. Replaced
> all connections to the starter, replaced the starter and still no go. My
> battery charger is not one from the 60s so it doesn't have at 'trickle
> charge' option, just a manual/automatic and either one I choose it still
> reads 14 volts fully charged.

I don't think you have a battery problem. It sounds more like a connection 
problem somewhere in your circuit.

First, where are you measuring the voltage when you see 3 volts? To get a sense 
of battery condition, do this measurement from post to post right on top of the 
posts (not touching the clamps.) If you get 3 V from the fuse box to ground and 
12 V from post to post, then you have 9 V of voltage drop in some connection 
somewhere.

If you see the post to post voltage drop to 3 V when trying to start, then I 
agree that your battery is shot (but there's a remote possibility that there's 
something seriously wrong with your starter. Very unlikely, with 2 starters in 
a row.)

WIth someone else turning the key, start measuring the voltage drop across each 
of your connections. Here are the places you need to measure: post to clamp 
(both posts), ground cable to chassis, starter cable to starter post, starter 
body to transmission, transmission to transmission ground strap, transmission 
ground strap to chassis.

Each of those measurements should show zero V if the connection is good, but 
I'll bet that you're going to find ~9 V of drop across one of them. Once you 
find that drop, that's the connection that needs help.

> Perhaps $90 is not enough to spend on a battery. How long do you usually get
> on your batteries? 

It's been awhile since I last bought a battery, but I've never spent more than 
$80 on one for my VWs. I think the last one was something like $78, but that 
probably comes to $90 today. I usually get 5-8 years out of a battery.

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