Philes' Forum by Vic Lucariello

Hello, bimmerphiles! In keeping with the theme of Philes' Forum's tenth anniversary, here is the opening paragraph from the February, 1988 edition:

"There may be some truth to the contention that BMW owner demographics are changing. I still can't believe my eyes, but a couple of weeks ago, I saw a brandy-new, arrest-me red 3-series sporting a genuine imitation chrome-plated aftermarket hood ornament! You know the kind. They come in various shapes (this one was bovine) and are available in stores like R&S and from that botique of byzantine bargains, J.C. WHITNEY. I guess it coulda been worse, though. At least the 3-er wasn't sporting a bumper sticker and/or one of those "CRETIN ON BOARD!" rear window signs to complement the hood ornament! Come to think of it, it coulda been a lot worse. Suppose it had been an '02!! Then I'd probably be writing this from the Hunterdon County Jail! Talk about desecration of national treasures......"

Speaking of J. C. Whitney, I found an item in their catalog that will help eliminate the problem of your Bimmer's battery going dead when you let the car sit unused for awhile.

The proliferation of electronics in motor vehicles has resulted in increasing amounts of parasitic current (The battery current which exists even when everything in the vehicle is turned off). I measured this current in my stock E30 M3 to be about 30 milliamps (0.030 amp). (Techies: That flashing LED on the anti-theft radio consumes about 10 milliamps [ma]. Now you'll be able to sleep at night!) The parasitic current in my `88 Bronco is about 100 ma. An alarm system adds a bit more. In a stock 2002, parasitic current is almost zero. Anyhow, let a late model car sit for awhile and you may end up with a dead or weak battery. Indeed, several of you have called and described this exact problem.

The extent of this problem is such that new Bimmers are shipped with temporary battery disconnect switches. Part of the dealer prep procedure is to reconnect the stock battery cable and remove the switch.

Of course, you can circumvent the problem by simply disconnecting your battery when your car will be sitting awhile. On recent Bimmers, however, the battery is usually in a relatively inaccessible spot, and, even if you disconnect it, you'll need to reset your radio and trip computer when you restart the car.

Another alternative is to jump-start your Bimmer to get it going again. There are several reasons why I'm opposed to this, but for now I'll just say it's inconvenient and can be dangerous to both you and your Bimmer.

You could, provided electricity is available where your car is parked, hook up a small, trickle-type, battery charger (typically 1 amp capacity). The problem is that these inexpensive devices are not sensitive to the battery's state of charge. Once the battery reaches full charge, a trickle charger will continue to pump its one amp or so into the battery until all the electrolyte is boiled away. Ask me how I know this!

The best solution I've found to the problem is to use a J. C. Whitney Off-Season Automatic Battery Maintainer (Catalog No. 06PK4118P). This trick little device combines a battery charge monitor with a 1/2 amp trickle charger. It works by measuring the battery terminal voltage and controlling the charge rate such that terminal voltage is maintained at about 13.1 volts, which is only slightly higher than full-charge voltage. You can leave this little jewel connected for months and not have to add a drop of water to the battery! The best part of this is that the maintainer costs just $20 plus shipping. The current J.C. sale catalog lists it for just $13.99!

There a couple of caveats I found while evaluating a number of these battery maintainers over the past few years. I have them on all our Bimmers, the Bronco, the trailer brake battery, the lawn mower battery, my spare battery, even our home burglar alarm!

First, follow the instructions and only connect the maintainer to a fully charged battery, and ensure that all the vehicle's electrics are turned off. This is very important as this maintainer is an inexpensive device without the capability to limit its output current. If you were to connect to a dead or partially discharged battery, or if you inadvertently leave the key in position "1" and/or leave the radio on, you will overload the maintainer and fry it. Ask me how I know this!

Second, be sure to observe the correct polarity when connecting to the battery. These maintainers do not have reverse-polarity protection and will fry if connected incorrectly. Ask me how I know this!

Third, be sure to unplug the maintainer and disconnect it from the battery [in that order, Ross!] before you start your car.

You may be thinking that, well he thinks he's a wiseguy with his trick little maintainer, but I still have a problem accessing my trunk- or underseat-mounted battery. Well, if you cut off the positive and negative battery clips from the maintainer and install a cigarette lighter plug from Radio Shack [no soldering required, Ross], all you need to do to connect the maintainer is to plug it into the lighter socket, then plug the maintainer into an AC outlet. The maintainers DC wires are small enough so that you can close your car door over them without harm.

In addition to the maintainers I have evaluated, Joe Getcy and Hank Farber both have one, and they are thus far pleased with them. In fact, Hank also has a more sophisticated maintainer that costs more than twice what you can get J.C.'s for on sale. I evaluated Hank's, too, and didn't find any significant performance advantage.

I would be remiss, and Ross would no doubt chastise me, if I didn't again tell you to be careful whenever you work around batteries. Be sure you have eye protection on whenever you attach/detach any battery clips or terminals. This is another advantage to the cigarette lighter plug approach: It removes you from the proximity of the battery.

Anyone wishing to contribute to Philes' Forum should contact me via the info on the masthead. I'm interested in tech tips, repair/maintenance questions and/or tips, dealer horror stories, product evaluations, etc. Please call before 8 PM, and if you leave a message, PLEASE INCLUDE YOUR WORK PHONE NUMBER. Also, please be patient, I try to return every phone call, but it sometimes takes awhile. The best way to contact me is via e-mail.

Copyright 1997 - V. M. Lucariello, PE