Electrical problems after dead battery

[Jay Laifman]

My battery went very dead a few weeks ago because the trunk was left open for an extended period of time. Once I got the battery to hold a charge and get fully charged, the car has had some odd electrical issues.

The CDR-220 radio stopped working entirely and the automatic click to open or close the passenger door window stopped working. But the window would go up and down, just not automatically. This is in my 2000 Boxster S (same radio as the 996).

Then after a couple days of driving, the window miraculously started working again.

Then after a few more days, the radio will now actually turn on. But the buttons are not functioning 100%. Like two of the 10 station buttons would not do anything on FM1, but works fine on FM2 and AM. As I pulled in to work, it now seems like they were all working. The balance and fader buttons seem off too.

What gives? Will it all fully come "back to life"? Are there electrics in the engine that might not be working 100%? So odd.

I read a bunch of posts about people who said their fuse in the back of the radio blew after a battery went dead. I was assuming that was what happened to mine. So I was in shock after a few days that the radio is "curing itself" which I believe be somewhat impossible. Yet it happened right in front of me.

Didn't get abducted by aliens though. .. yet.

[wwest]

I assume that you started the engine by "jumping", in which case once the engine started the battery was so low in SOC that it would not play its part in regulating the alternator output.

That would be much like disconnecting the battery with the engine running which often results in the alternator voltage output "going into orbit", voltage spikes as high as 30 volts.

Electrolytic capacitors, used throughout the car's electronic componentry, develop leakage at excessively high voltages, some will "heal", recover, some will not.

It's NEVER a good idea to jump start a car with a dead, fully dead, battery.

Good luck.

[Jay Laifman]

Thanks for the thoughts! Actually, no jump start. I charged the battery with my charger. It actually wouldn't first take a charge at the 10A setting. I had to put it to the 2A for a long time and it finally fully charged. Then I started the car with the fully charged battery.

[steely]

That does sound serendipitously weird. I usually had to enter a security code into our non-porsche radios if the battery was changed/disconnected (or died) and I had to reset/reprogram the wireless keys. Nothing ever came back from the dead like that for me.
I do know that sometimes if the voltage is less than optimal you can get some ghosts in the machine - just enough to do some strange things.

Are you able to reprogram the FM1 stations now?

[pmax]

Replace the battery.
It's not going to last long anyway.

[Jay Laifman]

I will check if I can reprogram.

Yes, I initially thought it wasn't working because it needed the code - which is in a folder in the house. So I first ignored it. Then I got the code card and went to put it in. That's when I found the radio was dead. It wasn't even asking for the code. I searched on line and found references to that back fuse blowing. So I ignored it for a second time.

Believe me, I want to think I just missed something. But, I'm not a novice to working on cars! This is odd.

And the crazy thing is that I wouldn't have known anything changed, except my wife drove the car yesterday and told me the "radio was working oddly." I was shocked because it wasn't working at all.

And here is the last tricky, odd thing. I NEVER put in the code!

[Jay Laifman]

Originally Posted by pmax

Replace the battery.
It's not going to last long anyway.

It is a 7 year battery with only 4 years on it. On Monday, I actually will be at my mechanics where I got the battery for an alignment. So I'll have them check it.

Thanks

[DRACO A5OG]

DO you have your owners manual?

I recently had a new battery installed in my wife's CLK320 and the wrench had to reset the auto window feature by holding it in the up position for 3-4 seconds after it went up.

He said allot wrenches do not know about this feature so many have auto windows that do not work because of the lack of the reset procedure.

[wwest]

Originally Posted by pmax

Replace the battery.
It's not going to last long anyway.

What leads you say that? He recharged the battery using the very best method possible.

[Jay Laifman]

Let me add these: When I tried to charge it at 10A, after about an hour or so, the charger would read that there was a fault and stop charging. I tried this a few times. Then I put it on 2A and it chugged along for a day or two and then indicated that the battery was in fact "FUL" - which it says on a complete charge. That said, when I do start it, it seems like it might not spin as fast as it used to. Can't say for sure though. So I'm not so sure there isn't something wrong after it discharging so much. But I don't know for sure. I'm looking forward to any information pmax provides.

[steely]

Disregard me if you did this, but did you check the voltage with a meter and verify the fluid level was alright?

[DRACO A5OG]

Take the battery out and have it tested at a FLAPS of AAA. Just to remove the battery from the list.

[pmax]

Originally Posted by Jay Laifman

It is a 7 year battery with only 4 years on it. On Monday, I actually will be at my mechanics where I got the battery for an alignment. So I'll have them check it.

Thanks

Why risk messing up the alternator or worse, your metalwork from an acid boil , for the price of a new battery ?
It is a 911, right ?

Originally Posted by wwest

What leads you say that? He recharged the battery using the very best method possible.

The chemical changes in the battery when fully drained are irreversible.
The fact that it doesn't hold a charge at 10A is telling.

[wwest]

Originally Posted by Jay Laifman

Let me add these: When I tried to charge it at 10A, after about an hour or so, the charger would read that there was a fault and stop charging. I tried this a few times. Then I put it on 2A and it chugged along for a day or two and then indicated that the battery was in fact "FUL" - which it says on a complete charge. That said, when I do start it, it seems like it might not spin as fast as it used to. Can't say for sure though. So I'm not so sure there isn't something wrong after it discharging so much. But I don't know for sure. I'm looking forward to any information pmax provides.

"Smart" chargers will often fault out with a deeply discharged battery, often takes 3-4 days on a simple (shall I say STUPID?) battery charger to recover a deeply discharged automotive battery.

Also, connecting a reasonably good low SOC battery in parallel works to "fool" the smart charger.

"..not spin as fast.." Give it time, your car's alternator/VR system will raise the SOC above what most chargers will do, certainly so for a charger in the short term.

Battery chargers go into float mode once the battery reaches an "acceptable" SOC, your car's system just keeps on producing ~14 volts, provided it can (RPM + load), regardless of battery SOC.

That's why it is not wise to use the car's system to repetitively recharge a dead battery, it can/will eventually boil the electrolyte away.

[wwest]

Originally Posted by pm ax

Why risk messing up the alternator or worse, your metalwork from an acid leak , for the price of a new battery ? It is a 911, right ?

To my knowledge recharging/recovering a DEAD automotive battery with the host system will have no adverse effects for anything other than the battery itself.

The chemical changes in the battery when fully drained are irreversible.

In the short term, yes, but just as Op experienced the chemical changes are reversible with time, patience, and the right charger.

Try it the next time you think you have fully drained battery, connect a simple trickle charger, say 2A, for three or four days and then connect a "real" charger.

Acid leaks results either from a cracked case, or from boiling the electrolyte. The latter generally only happens when the VR has failed and is overcharging the battery.

[Discseven]

Originally Posted by wwest

It's NEVER a good idea to jump start a car with a dead, fully dead, battery.

Will... what about clutch popping?

[wwest]

Originally Posted by pmax

Why risk messing up the alternator or worse, your metalwork from an acid boil , for the price of a new battery ?
It is a 911, right ?




The chemical changes in the battery when fully drained are irreversible.
The fact that it doesn't hold a charge at 10A is telling.

That wasn't an issue of not holding a charge at 10A.!!!

A "smart" battery charger will quickly detect that it must raise the charging voltage beyond a specified design level to force a 10A charge rate into a fully discharged battery.

[wwest]

Originally Posted by Discseven

Will... what about clutch popping?

Same problem, if the SOC is good enough that the battery accepts an alternator/VR dictated charge rate it WILL boil the electrolyte. Repetitively doing so without solving the core problem and the electrolyte will get down to.....

Not saying that we ALL haven't done either or both quite satisfactorily at some time or another. Just not, hopefully, multiple times on the same vehicle/battery.

Not always possible to do it the RIGHT way.

[ischmitz]

Besides discussing all the theories and "possible scenarios" I would do a couple of simple MEASUREMENTS with a DVM:

- voltage with ignition on and engine not running (connect meter to battery poles)
- same while cranking
- same while engine idling
- same while reving engine to ~3k

If you have access to an oscilloscope and are able to measure ripple while the engine runs that would be a plus. Then report back

edit: didn't realize this was a 2000 Boxter. The alarm control module stores Vbat failures as a permanent fault code. And so do some of the other control modules such as DME, TCD, etc. The windows also have its own control module. Your best bet is to hook the car to a PST-2 or PIWIS and reset these codes and take it from there.

Ingo

[Tremelune]

Everyone with a battery should own at least one Battery Tender Jr

Put it on every time you park the car in the garage.