Dead battery

I have a dead battery. There are many others like it, but this one is special. It is the sixth new battery in as many months. I replaced it on my own the first time and since then I have gone to the dealer. 1st battery) Porsche battery. Could have been original. No idea. Replaced it with Die Hard International. 2) Porsche said the Die Hard was insufficient despite better specs than Porsche battery. They would only support the Porsche battery. 3) Faulty hood switch (light didn't always come on) 4) Alarm control unit drawing more power than expected. Replaced. 5) Couldn't find any problems. No significant draw over six days in the shop. I'm on my own. 6) Just happened. No readily apparent reason. The first two weeks after the very first battery died, I kept a log of voltage and current measurements and tests that I performed manually to troubleshoot. No patterns or significant anomalies emerged, so I replaced it. Since then, I just let the dealer handle it, but now that they've thrown up their collective arms, I'm on my own. I have a few thoughts on how to proceed and I would like to hear from a sounding board. A) Troubleshoot the technical problem on my own . . .1) Datalogging . . . . . . .a) Does a pre-existing plug-n-play electrical system datalogging solution exist? . . . . . . .b) Develop a new solution to datalog this B) Work around the problem . . .1) connect the car to a trickle charger every night . . .2) carry a portable emergency battery C) Is there a legal approach . . .1) Is the dealership responsible . . .2) Is the aftermarket warranty company, Western General, responsible? Your thoughts appreciated.

I'm frankly amazed that any shop would replace six (!) batteries in six months without finding a problem with the charging system.

Amazing... But you should be able to figure this one out. A battery can be discharged quite a few times and still be a good battery if the current draw and subsequent heat generation are very low. Your condition, IMO, describes a large current draw and high heat generation. I would know because I used to be in the high-end car stereo business and these amps used to draw over 100 amps of current. My batteries would only last a few months... So whatever is happening, it is probably intermittent, but probably also very noticeable when it IS happening. The first question I have is: how do you know that your alternator/regulator isn't frying your battery with excessive voltage? If the car doesn't do it for 6 days while sitting around, it may be doing it while the car is running. Put a volt meter on the car and have a look.

DO YOU HAVE AN AMP METER?

Thanks. Everything you've said makes sense to me. The alternator/regulator were brand new, along with an entirely brand new Porsche factory engine a few months before the problems began, and also, the system was verified during at least one of my visits. Sure, of course I have a volt meter and I've been using it, pulling each fuse individually and logging the draw...nothing to see here, nothing to see here. I totally agree! This is why I'm interested in the datalogging solution. Actually, I logged the voltage at 12.65V before going to bed and it was 10.58V (dead) upon waking today. That's a big draw. I believe that I would need to take samples at least once an hour to catch it in that act and then I would need to be able to trace the circuit after that. As a point of reference, I have found that below 11.50V, the potential is insufficient to start the car.

My wife used to have a 325i, It had this issue that it wouldnt go to sleep (sounds like my 4 month old son) Seriously though, the computer wouldnt put the car in sleep mode, so the battery would die in a few days if not driven. New computer and all was well

this is for other cars but the same principles applies to all cars. click below: http://www.cardomain.com/ride/2379797/8

Thanks for the thought. They considered that might have been the problem so that was reconciled when they replaced the alarm control unit for battery #4. Mine is a daily driver, though on most days it's just 3.0 miles to work, then back, then 1.5 miles to the gym and back. I've read that in Japan, dead batteries are common because the congestion and short commute do not give the charging system enough ability to recharge the battery, but the dealer isn't buying that and given that my battery lost 2V potential overnight, I am also losing faith in that possibility.

Yep, that's were I start. If there is significant draw, then I will do the same thing, per circuit, at the fuse panel, to track it down.

Do you have a separately powered sub-woffer in the car? Is there anything drawing directly off the battery? It sounds like a situation I had with a neighbor who put in a powerful sound system. It had a capacitor that would drain slowly and during some testing it simply did not detect because it did not require current. Then it would leak down and ZAP the battery for a quick but heavy load. And on it went.........

Sadly, no subwoofer, though I did add an iPod (more generally, I've only added an AUX in cable, but I use it for my iPod shuffle -- audio only -- there is no power supplied to the iPod). It's been a while, but it is possible that it was around the time of the first incident. However, this too, has already been explored as a possible cause and ruled out by the dealership. All I've done is added the auxiliary input cable provided by the OEM of the radio, Becker Auto Sound, then extended it with an RCA <-> mini-headphone cable. The first $2 cable would experience high attenuation from time to time which was remedied by shaking the cable, so I replaced that w/ a high quality gold plated cable and the problem is no more. Normally, I power off the iPod when I leave the car, but sometimes I forget and with a 19 hour battery life, the iPod is sometimes dead the next time I want to use it. There has been no correlation between the times I've left it running and the times when the car battery is dead. Since the #5 battery situation, I have never even attached the iPod (only the cable remains) and the battery has died. Am I overreaching to think that removing the cable is a reasonable troubleshooting step? There is exposed metal where the RCA cable meets the Becker AUX input cable.

One idea is to pull 1/2 your fuses and check the battery in the morning. If dead, you just ruled out 1/2 the fuses. Next, pull 1/2 the remaining 1/2. Keep doing this until find the draw. Of course, this could take some time and you could end up with a fried battery each time. If you cannot afford to keep replacing the battery, then you might just stay up all night with the car, and sleep next to the ammeter with alarm clock waking you up every hour...

Binary search pattern could take months if mean time between failures remains around 4 weeks and that's a little longer than I can go without sleep :-) I'm going to go with a long term, overnight datalogger. I'll start by checking out what the dealer mechanic was using and go from there. Until I get that system in place, I'm just leaving it on the trickle charger every night. Thanks for all the thoughts and suggestions!

do you have an amp meter or a volt meter?

I have both. Volt meter to check the potential of the battery and ammeter to check the draw on the circuits.

how are you hooking up the ampmeter

Inline with the circuit. When measuring total draw, I connect to the battery as described in the URL of a previous post and when measuring per circuit, I replace the fuse path with the ammeter.

as a side note, i remember someone on this board had a batt. problem turned out to be an umbrilla under the seat, it hits the seat adj. buttons periodically.

That's exactly the sort of thing I'm hoping for. My fiance once had a rattle in her car and I just never had time to check it out, so we took it to the dealer and the mechanic said, "uh, did you know you have a screwdriver, license plate holder and some books in the trunk." No. No, I did not. ugh.

un hook the ground from the battery run the ampmeter from body to battery inline do not try to turn the key on or start the car latch the front latch and the drivers door leaving them open lock the car with the remote let it sit for 15-20 minutes whats the amp draw

All I can say right now is >200mA because my ammeter doesn't read any higher. Having said that, the battery was quite dead (8.53V) this morning. I'm getting a higher capacity ammeter and I'll try again.

Holy cow! There is now a persistent 2.75A draw when the car is off, closed and parked. After arming and leaving it site 30 minutes it dropped to 2.65A, but clearly, the lesser current experienced in sleep mode is insignificant in this scenario. I pulled every fuse in the driver footwell area and well as every relay in that area and there was no change. Then, I pulled every relay from the second relay station, behind the driver's side rear seat and there was still no change. Wiring diagrams suggest only three remaining paths which bypass those systems, those being 'ABS/PSM', Ignition lock and terminal 30 disconnecting point, which goes to the starter. At this point, my educated guess is a partial short circuit. The fact that the engine was replaced lends credibility to this supposition, IMO, as a wire may not have been routed correctly during the install. Rather then disassembling things, and since it is under warranty, I'm going to go back to the dealer with the belief that they must at least admit there is a problem with 2.7A draw when the car is at rest.

At least you found it. I don't know why the dealer couldn't find it those 6 days they had it. It could be a short, but I doubt it's a short on the terminal 30/start joint, since a short like that could draw much more current. Sounds like an electric motor or light bulb...

Quickly closing the loop on this...it was the alternator. The dealer determined that the brand new alternator, which they installed a year earlier, was bad. R&R and it's been great ever since.

Quotes source post: 4520454

It's hard to believe that after 6 batteries the DEALER didn't bother to check the alternator. I'm not a certified tech, but c'mon, it was 6 dead batteries. Did they really think that after the first 2, 3, or 4, that they could just replace batteries until you gave up on the car. -td <-- wouldn't be going back to that service shop

Yeah, that's Car Tech 101, IMO.