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Tuesday, April 23, 2024

Doug's Domain

Doug Vetter, ATP/CFI

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Wednesday, July 21, 2010

Battery Failure

The day began like any other. I walked out to the car, hopped in, and turned the key. Except this time the car didn't start. No slow spin of the starter. Not even a solenoid click. Just one key chime and the faint glow of a few annunciator lights that reminded me of the last scene in an Airwolf episode called Moffett's Ghost. "Hmmm", I said in my usual sarcastic inner voice, "this one is going to be hard to diagnose."

Normally I'd be well set to handle a situation like this but suffice it to say that my current living arrangements are less than ideal, with my backup car, backup battery (the one I pulled out of the car three years ago) and virtually all of my tools at another location. I did have a volt-ohm-meter (VOM) on hand so I checked the battery and found it at 10.9 volts. Now all I needed to do was determine WHY the battery was discharged.

The vehicle has been starting well and gave no indications of a charging system failure on the drive home the prior evening. I also didn't do anything stupid like leave the lights on overnight and the car is not equipped with an alarm. That meant either some silent accessory in the vehicle was drawing power and pulled the battery under or a cell reversed and the battery was toast. Based on the fact that the battery did not turn over the starter and did not "recover" with the key off as most discharged batteries will, instinct told me it was time for a new battery. Since the E36 is fairly "old school" and more tolerant of a defective battery than the newer vehicles I figured I'd call a local tow company to try a jump start then drive the car over to my garage to get the E46 that I could then use to get the new battery.

When the tow truck arrived the driver connected a 20 foot jumper cable between a jack on the truck and the battery. After a few minutes of charging the starter reluctantly turned over the engine and it settled into a smooth idle. I let the engine idle for ten minutes while the driver wrote up the paperwork and I continued troubleshooting. I put the VOM on the battery terminals and found the voltage at 13.9. This meant that there was enough juice in the battery to energize the field and that the alternator was capable of producing a high enough voltage to run the car's electronics. This increased the likelihood that the battery was at fault and hinted it would be okay to drive the vehicle the few miles necessary to reach my garage.

When I arrived at the garage I strategically parked the vehicle knowing full well that the battery likely wouldn't start the engine again. Needless to say, I wasn't surprised when I shut the car off and then turned the key again, only to be greeted by a sickly rapid key chime -- a tell-tale sign that the vehicle's systems were not receiving full voltage. Since the 15 minute drive would have sufficiently recharged an otherwise healthy battery, this confirmed the diagnosis of a reversed cell.

I got out out of the car, grabbed a 13mm shallow socket and small ratchet, and removed the battery ground terminal followed by the positive. Then I used a 10mm deep socket and 3" extension to remove the retaining bolt, pulled the battery out and plopped it into the trunk of the E46. I then drove over to my dealer and picked up a new battery for $111. Of course my technician saw me waiting at the parts counter (again), feigned surprise, and asked me "Hey, where's your uniform? You're here all the time...you might as well wear one!"

This evening I stopped at the garage on the way home from work and installed the new battery. The vehicle started enthusiastically so the battery appears to have been the problem. However, because I'm skeptical by nature I brought the backup battery, the tools necessary to swap it, and my high current battery charger home with me just in case history repeats itself tomorrow morning.


I have replaced the battery twice over the life of the vehicle. The original battery was replaced in my first maintenance binge back in June of 2002 when the vehicle was a bit over four years old. That battery, in turn, was replaced back in September 2007 in accordance with my maintenance schedule when it had been in service for five years. The core charge on the battery was only $5 so I kept the 2002 unit as a spare and keep it topped off with a Battery Tender.

I don't know why the 2007 unit failed prematurely but my guess is, like everything else, general manufacturing quality has dropped in order to help BMW's bottom line. BMW batteries were once supplied by Douglas (not me) and in 2006 they switched to Exide. The battery I installed in 2007 was therefore an Exide unit though I don't recall seeing an Exide brand on it. The new battery I installed today has the Exide name prominently displayed on the label.

The general consensus online seems to suggest that Douglas made good batteries and Exide quality is not up to par with the Douglas. Still others have suggested that Exide simply bought the Douglas factory so the batteries are made to the same standard of quality. In any case I can't make a judgment based on a single event but I won't be surprised if the new Exide unit fails in under three years. If it does I'll change my maintenance schedule at that time to reflect the new reality.

Most dealers, incidentally, get $90 to install a battery and of course they charge full retail for the battery which is $140. That means I saved $90 in labor and about $30 in parts doing this job myself.

Mileage: 194515, Labor: $75, Parts $111, Parts Saved: $29, Labor Saved: $90