Battery dying? alt. problem?

magilla · 02-10-2002, 06:31 AM

OK, electrical stuff is pretty well beyond me. I never quite understood it beyond the theoretical taught in physics and circuits I. Here is my dilemna:

I don't don't drive my SC much in the winter, and it sits in the garage at my office. Every couple of weeks or so I go and fire it up, warm it up, and drive it around for an hour or so. The last few times I have done this, the battery played dead- turned a few times and then nothing. as soon as I wired it up to the family truckster, it immediately (within 1 minute) fired up and ran like a champ. It would restart countless times after that without problems. Next week, same problem. Is this my battery crying for replacement, or is this a alternator thingy problem? Is this just the cold? Any thoughts?

Thanks,
Magilla

rstoll · 02-10-2002, 06:40 AM

My 83 is the same. I only drive it on weekends. About every couple months or so I have to give it a good charge. Battery and alternator are ok. Just needs more seat time.

magilla · 02-10-2002, 06:46 AM

Now that's a DIY fix I can enjoy!!!!

Little chance of failure on that one.....

Thanks!

Formerly Steve Wilkinson · 02-10-2002, 07:11 AM

Ditto my '83 SC. I think it's that there are enough tiny draws in wiring that old--leakages, really, that don't constitute true shorts--plus the electric clock, that the battery will inevitably run down over the span of a few weeks or a month. Which is one reason Porsche people favor Interstate batteries: that sort of regimen--fully charged, dead, fully charged, dead again--is bad for a battery though it's typical of a lot of winter-stored 911s. Interstate provides a non-prorated guarantee even if you mistreat your battery in this way.

Stephan

pbs911 · pbs911's Garage

I have seen even newer Porsche lose the battery charge in a week of not starting the motor.

The problem is that jumping the car and allowing the alt to charge the battery is NOT good for the alt. There is a good possibility you will need to replace the alt by the time spring comes around and this rate.

It is best to hook up a trickle charger to avoid this.

scedmonds · scedmonds's Garage

Double-check that the battery is getting charged when the engine is running . . .

My alternator died within two weeks of getting the car in my hands; had to replace it and the regulator AFTER I replaced the battery but DIDN'T check that it was being charged.

Cheers!

C.

bigchillcar · bigchillcar's Garage

ditto...

if it has to sit up for weeks at a time, put it on a trickle- charge in your garage if at all possible. that will keep it fresh as a daisy!

stlrj · 02-12-2002, 09:19 AM

Is it possible that the battery is just getting old and tired?

Joe

82SC · 02-12-2002, 09:27 AM

on a related note...

I had my alt changes with a BRAND new one last year...
I don't have starting problems...but after start up my headlights and guages are dim...and get brighter as I rev...

this goes away once my revs stabilize and the car is warmed up...

could it be I need a new battery?
I drained it once after leaving the reading light on for 3 days straight....and it too a really long jump start to get her going...

I would rather change out the battery so I don't ruin the alternator...

thanks

MJ

bigchillcar · bigchillcar's Garage

hey,
i'm not very familiar with the sc cars, i've got a '74, but in my car the red generator light illuminates upon starting and i have the same symptoms. until the engine speed hits in the neighborhood of 2300 rpm's the light won't extinguish because the extra rpm's are needed to 'excite' the alternator components. an actual generator will operate at lower rpm's, but an alternator needs more speed to start functioning. this is normal alternator behavior and thus your lights will brighten once it comes online. if the car were allowed to sit for a while without exciting the alternator, the battery would eventually discharge. anyway, hope i'm not telling you something you don't know already.

82SC · 02-12-2002, 09:16 PM

nope...good to know

thanks

MJ

and welcome to PPBBS

john walker's workshop · 02-13-2002, 07:49 AM

batteries are generally good for their stated life expectancy. 60, 72 months. after a long slow charge, test the gravity of the fluid with a hydrometer. the cell readings should be in the middle of the good range. if you find one or more cells in the fair, or poor range, or cells that peg the needle at the top (sulphated), the battery is probably over, regardless of it's proposed lifespan. the next test, after it's fully charged, would be a load test, but you would have to take it to a shop. 150A for 15 seconds, and watch the gauge for how low the voltage goes. it should hold at least 10.5 V during the test. if it drops to 5 or 6, it's tits. lots of batteries sit in warehouses for a long time, decomposing, before they're shipped to schucks.

magilla · 02-13-2002, 08:37 AM

What's a trickle charger? Is it a regular charger? Where can I get one? Local?

Thanks,

David McLaughlin · David McLaughlin's Garage

Or, Magilla, you could listen to me. I have a trickle charger and it worked great. You (we) should clean all of the chassis grounds and check their condition. If the problem persists, change the ground wires. If there is still a problem, look at a new voltage regulator or alternator. This is of couse all after you (we again?) check the battery.

This is what I have. I can keep my car on it all winter if I wanted to. A cool feature is that it has a plug that connects to the battery terminals so that the charger doesn't need to rely on faulty clamps.

It was less than $25.00
http://www.batterychargers.com/details.cfm?prodid=SE%2D1562A&catid=16

jeff91C2T · 02-13-2002, 10:04 AM

Odds are your battery is ruined due to lead sulphation as JW pointed out. Your never going to get a full charge. Seems to be fairly common problem with P-cars. Probably due to long periods of sitting. Keep in mind, even if you disconnect your battery, it will still slowly loose charge. And when the battery voltage goes below a certiam amount, lead sulphation starts to occur.

I've been trying to revive one of my sulphated battery's with a pulse charger with limited success. The only real solution is a good trickle charger and keep it topped off.

Here is a great FAQ about battery's...

http://www.uuhome.de/william.darden/

Joe Bob · Joe Bob's Garage

A trickle charger is a 2amp (slow) charge. You can get the handy dandy ones that permanently mount to the battery and just plug it in before long periods of storage or the Sears variety has the 2 amp/10 amp option ones....

BTW, if you get the battery mounted ones, make sure it's one that shuts down after full charge or you can cook the battery...even at 2 amps.

As to batteries dieing after 3-4 days, BTDT. I replaced a battery that tested fine, but died with an Optima. Left it for five days and it fired right up....looks like it was a tried battery after all.

YMMV

Z