dead battery, fast

[timothy208]

i have a 1999 boxster, and the battery keeps draining, dead, where is a good place to start to diagnose this problem

[JFP in PA]

With a parasitic drain test.

[mikefocke]

Your battery is fine when jump started and charges fine

but discharges quickly with the key is turned off and removed?

disraeli posted this on Porsche Pete's Boxster Board (*)

"The factory technical manual (Section 97-07 page 2) has the following table of total electrical load after the car has been shut off (ModelYear 02):

(electrical current is worst case, i.e. car loaded w/all options...)

FROM TO mA

0 min 5 min up to approx. 950

6 min 15 min up to approx. 900

16 min 20 min up to approx. 750

21 min 60 min up to approx. 50

61 min until the battery is empty up to approx. 30

1000mA equals, of course, one amp.

If the car had no options whatsoever, the load after 60 min would be 17mA instead of 30mA.

From this table you should be able to insert an amp-meter between the battery and battery cable and tell if the car is within spec before you begin pulling fuses or removing the battery to get it tested."

And once you see the draw is beyond spec, you pull one fuse at a time noting if the current draw drops within spec when the fuse is removed. Find the one that causes the excess draw and you have located the circuit that is causing your problem.

Richard Hamilton provided this:

A useful tool for monitoring battery condition over time is a Ancel Battery Monitor. Bluetooth, allows monitoring battery voltage via an app on your phone.

A old table of the electrical draws is at https://sites.google.com/site/mikefocke2/batteries most of the other stuff is outdated or relates to what I did but the tables should be useful.

Have you done anything recently to the car? Audio? Had any other issues? Does it seem that the key actually turns off the accessories that might be creating the draw?

[husker boxster]

If this is a recent occurrence, has there been any electrical work done lately?

[Litesonic]

Had a similar issue... bought a battery... nope.

Did a parasitic draw as the the trickle charger wouldn't keep up anymore. No obvious culprits in the fuse panel area.

Changed just the voltage regulator on the alternator as it appeared that was the culprit.

Then the entire alternator bit it.


Swapped in a new alternator, no issues since.