Spontaneous Regeneration

Doug&Julie · 05-01-2006, 04:07 PM

Some of you may know if my recent issues with the old car and "dead batteries". If not, my thread is here:

http://forums.pelicanparts.com/porsche-911-technical-forum/279055-early-911-batteries-101-help-post2560753.html#post2560753

So today...after the car hasn't started for about a week and a half...I thought, what the hell, let's see if it starts up. I grabbed the keys and, without even sitting in the car, reached in and gave it a quick turn. I got a crank! So without further ado I immediately sat in the car and proceeded to attempt the start according to "directions"...turn the key for a few seconds...pump the gas pedal three times...then turn the key all the way and....bwah....bwah....bwaWRUMMMMWRUMWRUMWRUMWRUMW RUM!!!! Keep it fired Doug! Keep it fired! OH baby!!!!

Needless to say, I took it out and drove it around for, oh, 45 minutes or so. It's a beautiful spring evening here in the Cinci area...perfect early 911 driving weather. About 66 degrees. Mostly clear. What a great night for a drive. (..even if it was in a lot of late rush-hour traffic..)

And if the weather is good, I'll for sure be driving it again tomorrow. And the next day. And the next....

But I'm perplexed as to why, after a number of tries over the past week and a half, the car only decided to start tonight? Is my "dead battery" diagnosis wrong? Is it possible for batteries to 'go bad' in a year? (..these were purchased by the P.O. only a year and a few months ago..)

I suppose I shouldn't complain...unless the car doesn't start again tomorrow. But I should hope a 45 minute drive should charge those batteries up enough to last a little while, especially if I can drive it more often now.

Old 911s...

1982911SCTarga · 05-01-2006, 04:33 PM

Quote:

But I'm perplexed as to why, after a number of tries over the past week and a half, the car only decided to start tonight?

There could be a host of issues at play -- a bad ground or one or more dirty, loose corroded connections, etc. Work the problem lest you get stranded somewhere.

Brian

mede8er · mede8er's Garage

Hehhehheh...the car will only leave you stranded on a cold rainy night when you've strayed too far from home....

wholberg · wholberg's Garage

In layman's terms, if the battery is fully drained, once the current drain stops, the chemical reaction in the battery will "regenerate" some available electricity. It will not be as much as a new battery, and repeated draining of a lead-acid battery causes sulfation of the plates, thereby reducing the available surface area for the chemical reaction, which is why repeatedly draining a battery reduces its capacity.

Perhaps you had a stuck switch, or something, that was causing a steady drain on the battery. I have had a similar problem with my 11 year old stereo amplifier, which only intermittently shut off when the car was turned off, causing the battery to drain overnight. Once I identified the problem, I removed the fuse from the amp and have had no further problems. I will either replace the amp or wire a secondary relay that shuts off power to the amp when the ignition is turned off.

lateapex911 · 05-01-2006, 06:07 PM

One other point...temperature plays a role. Cold slows things down, and if you leave a battery out in the freezing temps, and it's not charged...well, my luck has been bad with that combo!

Doug&Julie · 05-02-2006, 03:30 AM

I was certain cold had everything to do with the problem when it first started...in March. But it's been pretty consistant temps here lately, and I always tried to start the car in the afternoon, when it's warmest. Hmm...

FWIW I did give the batteries a good visual inspection before it started yesterday...no leaks, good connections (old, but clean), cables all look intact...I just don't get it.

wholberg, thanks for that explanation...it makes sense. When the batteries were "dead", the lights would still work, I could get the key buzzing, the fuel pump...er, pumping....everything but cranking the starter. I suppose they were right on the edge of "too low" and managed to push themselves back over?

By the way, how long of a drive should one take to charge low batteries back up?

oneblueyedog · oneblueyedog's Garage

The way I solved it after 3.5 years of twisting the key and buying every other part in the starter circuit except the starter motor and also creating an extra yellow jumper wire and measuring voltages to the yellow jumper (all good) was to get a Hi torque starter. No irritation now.

Hope you solve it more easily.

wholberg · wholberg's Garage

Quote:

Originally posted by Doug&Julie

By the way, how long of a drive should one take to charge low batteries back up?

Without an ammeter in the car, it's hard to know.

I think that your best bet for that battery is to take it out of the car and take it to a mechanic that can put it on a commercial charger. Commercial chargers use much higher amperage than the ones you can buy in the store, and some of them will "pulse" charge, which may remove some of the sulfation. The real long-term fix is to buy a smart charger for next winter. Whatever you you, have fun driving it this summer!

Doug&Julie · 05-02-2006, 04:33 AM

Thanks. I've got a "Battery Tender Plus" on order (backorder, in fact

) for the short term if they need help again. Long term...well, I won't have it longer than this summer. Did I mention my car is FOR SALE?

glenncal1 · 05-02-2006, 06:17 AM

I would look at your cables, and clean all connections, not just at the battery terminal. I would replace the cables if old.

Jeff · 05-02-2006, 06:32 AM

"Did I mention my car is FOR SALE? "

Doug, I guess you decided not to update the 70. What are you going to replace it with?

Doug&Julie · 05-02-2006, 06:37 AM

Quote:

Originally posted by C U L8R
Doug, I guess you decided not to update the 70. What are you going to replace it with?

Yeah, I just decided this early car isn't "it" for me. I'm going to get something more modern...maybe a 964 or Boxster S (..or 996 if I can stretch it..). The Subaru is also technically for sale, too, although I haven't placed any ads for it yet. I'm going back to one car. A Porsche as an all 'rounder.

I know I've waffled on this decision for some time, but now that it's been for sale, in my mind it's "gone". Even after a spirited drive yesterday (that I enjoyed a lot), I'm right with this decision.