Low Battery-Damage Possible ?

[orph]

Went to start my 930 this morning. Turned key and tach as well as boost gauge "maxed out" , but starter did not engage. Pulled light switch on and headlights were very dim. Obvious to me was the battery was almost dead. Pulled it from the vehicle and put on the charger. However, immediately upon turning on the charger, the gauge went "wild", pegging out to the extreme ( 25 V is the max gauge reading,) and then bounced around at the high end of the scale. I immediately disconnected.

Questions: with the tach and boost gauge maxing out when I first turned on the key, and the extreme readings when I put the battery on the charger, is there a chance I could of damaged any of the electrical components of the car ? Id the extreme readings on the charger an indication the battery itself has shorted out ?
The battery BTW is a Bosche.

[Jorgeman]

Orph--in all probability your gauges will be OK but that response to the battery charger is a bit weird! A couple suggestions:
1) Check the battery area in the car to make sure the battery didn't boil out over everything, If ANY moisture--immediately douse with bicarb. solution.
2) Check electrolyte level in the battery. Even maint.free batteries usually have caps you can pry off to check the level. If fluid is below the tops of the plates the battery may already be shot.
3) The battery isn't capable of putting out more than 12.6 volts so the gauges should be OK altho I don't really understand their pegging like that. However, battery boiling is a regular symptom of a bad voltage regulator/alternator so check your charging circuit as soon as you replace the battery. Have you noticed especially bright headlites recently?
4) Faulty grounds cause some very weird symptoms on occasion. If new battery doesn't square things away--check the battery and tranny ground straps. Good Luck.

[Wayne 962]

Here's a little known bit of information - Porsche explicitly says not to hook up a battery charger to the battery while it's connected to the car. Not sure why - people have been doing this for ages...

-Wayne

[dickster]

wayne

i think that would be for safety reasons. batteries give off explosive gases when being charged and really should always be removed to a well ventilated area for charging.

i'd say do that orph and give it another go.

[orph]

Thanks guys for the feedback !

I did pull the battery from the car before placing the charger on it. Tested each cell and all were pretty much "dead". Electrolyte levels were fine on all six.

Not sure how old the battery is, as it is the battery that came with the car when I purchased it, and I cannot find any markings or date code on it that would indicate how old it actually is. I do know that in the past, if the car sat for more than 2-3 weeks, it would go dead. So, we are going to purchase a new one and take it from there.

My only concern was the pegging out of the gauges when I first turned the key-never seen that before, and no, the headlights never seemed to be brighter prior to this event. My concerm became a little more intensified when I turned on the charger. and had seen the extreme output of the charger @ +25 and the charger's needle . Even with other batteries that were dead dead, had I ever seen the charger put out more than +15-16.
Just thought that was a little weird too !

Again, thanks for the input !

[Shawzy]

Battery woes...

I have just gone through battery replacement on a few vehicles and thought I would share with you a few things.

As far as testing goes, a good multimeter can tell you how your battery holds up over time and also how your voltage regulator is doing. You can pick one up at Radio shack or even the Home Depot i think. Cheap ones are $20, they go up to about $1000 for the best (e.g. a FLUKE meter). $100 should get you one that will hold up a while. This is a VERY handy tool around the house and is easy to use once you get the hang of electrical theory.

Your battery when fully charged should read about 12.6-12.8 volts. A dead battery reads about 11.9-12.2V. Check your voltage regulator and alternator by testing the battery while the car is running. With the battery hooked up to the car (one should never disconnect the battery with car running as you likely know already - the battery acts as a voltage stabilizer and prevents spikes etc.). Test the terminals of the battery - it should read about 13.4-13.6 volts (this is from memory - i may be off slightly) while the car is running. If it reads higher (14V+), or jumps around a bit, the voltage reg is likely shot. If it is lower than 13V, the alternator may be shot (or you may have a grounding issue).

Do a battery LOAD test. Batteries can be tricky. They can fool you if you aren't careful. Eg. You can trickle charge a battery overnight and find it reads 12.7 V in the morning. Great! You think. But, the sucker can loose it's charge after one start, and not regain, leaving you stranded wherever you park. I know from experience...

To do a load test:

1) Take a volt reading on the battery and make sure it's charged up (~ 12.6V); if it's not, trickle charge (@ 2amps) for 10-12 hours
2) Pull the cable on the ignition coil so the car can't start
3) Turn the engine over about 5-7 times
4) Take another volt reading - if the battery has dropped to less than 12.2V it is likely shot. It shouldn't drop more than 0.2 V if she's ok.

(note: instead of disconnecting the coil and turning engine over, you can leave your headlights on for 10min and then test the battery again - this helps if you may have a starter problem)

Do an ELECTROLYTE test.

Pick up an electrolyte tester - looks like a turkey baster with some nice colours on the scale. About $5 at your local auto hardware. By testing each cell with this tester it tells you if the electrolyte is any good. Know that when refilling cells use distilled water only.

BTW, most batteries last about 4-5 years.

If your old battery's plates had a lot of crap sitting at the bottom, it may be possible for them to short out (i.e. join together). That would mean when your charger is hooked up it would spike to max V because of the high current draw. I could be way off on this, it's just a guess. If it were true I would expect you to blow a house fuse or trip a breaker after 10sec or so depending.

Just so you know, my gauges in my 911SC spike out to the max momentarily whenever I start the car. Who knows why - I am confident is it not related to a voltage spike.

Good luck