I fitted a new Exide battery to my 98 A6 2.5 TDI in March (correct spec
The problem is that before I start the engine in the morning the voltmeter
shows the voltage as just over 10v. Once the car is started (a struggle
sometimes in cold weather) the voltmeter shows about 13v. If I stop the
engine and go back after an hour or so the voltage shows over 12v.
My feeling is that the battery is not holding the charge as it should, but
on both occasions that I have taken the battery back to the shop I bought it
at, it tests OK (well it would as I have just driven there). The alternator
test shows it is charging OK.
I would appreciate some feedback on what batteries should show on the
voltmeter before starting, after being left overnight.
With the engine off, the battery should read at 12 to 12.5 volts. With
the engine running, it should read between 13.75 and 14.25 volts. Based
on your description, it sounds like you have a bad battery.
Before you change the battery, you may check to see if you have a short and
a drain on the battery. This becomes more obvious after an overnight rest.
With engine shutdown check the current used; if it's excessive (not sure how
much, but say over 1 amp; ask a tech. on this), then start taking electric
fuses out until you find the culprit circuit and go from there.
If there's an amp of current being drawn from the battery when the car is
supposedly totally "off", there's something wrong.
With the car turned off, no lights on, no doors open, etc - I mean good and
truly "off", the only devices that should be drawing any power are the clock,
the "memory" logic within the audio system head, and the alarm system.
Between those the current should be well under 100 milliamps.
And a 12v battery reading 10v at rest is likely fatally damaged if not just
'00 s4 6spd
Yes 10 volts does not sound too positive. lol
You need to make sure that the connections are very clean and tight at the
battery, grounding cables from the battery, and also at the alternator.
Sometimes if the connections are not clean and tight you will lose voltage.
You can check this with your handheld voltmeter. Start testing voltage at the
battery terminals, then check the battery clamps, then hold the positive lead
from the voltmeter on the battery and touch the negative lead to the body of
the car. Compare results! If they are the same, you can test them with the
engine running. Then do the same type of test with the alternator, but the
engine has to be running. It is a little harder with your vehicle, but it is
doable if you make the connections BEFORE running engine. You are looking for
a drop in voltage which might mean too much resistance (not good). Then clean
any areas where you note this drop.
This is all assuming that the battery is good.
I just gained an extra volt when I cleaned the grounding spots on my
alternator. Hey that is like free power!! <g>
Others have told you to check for a drain too. That should be done first!
Good luck and let us know!
Before you criticize someone, you should walk a mile in their shoes. That way,
when you criticize them, you are a mile away from them, and you have their
shoes. Frieda Norris
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.