Philes' Forum by Vic Lucariello

PHILES' FORUM -January, 1999

Long time readers of this column may note that this installment marks the beginning of its 13th year of publication. YIKES! [No, Ross, looking at the pictures does not count as reading the column.]

Some columns generate more feedback than others. Positive feedback I don't mind. However, I do get annoyed when Big Al wraps a brick in one of my columns and throws it through the shop window! Two 'positive feedback' columns come to mind: The one I wrote a couple of months ago on battery maintenance, and the February, 1997 column on battery maintainers. Dave Gannon recently sent me an e-mail asking about the maintainer column, so I thought I would take the easy way out this month and rerun it with a couple of updates.

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 to the USA 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. Also, on some models, the Ni-Cad cells which maintain the service interval indicator will go dead after awhile. Moreover, Lead-Acid batteries self-discharge even when left sitting with no load whatsoever. I have seen published self-discharge rates of 1/2 to 1 % per day.

Allowing a car battery to sit in a partially discharged condition is not a good idea. A phenomenon called sulfation occurs wherein the Lead Sulfate which forms on the battery plates as part of the battery discharge process becomes 'hardened' after awhile and resists recharging. The result is reduced battery capacity, as the sulfated areas on the battery plates are effectively removed from contributing to the battery's energy storage chemical reaction.

Another alternative is to jump-start your Bimmer to get it going again. There are several reasons why I am 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. 06-4118). 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. [I recently verified that the device is still available from 'ol 'J. C.'.] Whitney's number is 312 431 6102. Visit them on line at www.jcwhitney.com.

There a couple of caveats I found while evaluating a number of these J.C. battery maintainers over the past few years. I have them on all our Bimmers, the Ford Pick-Up, 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 backwards. 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, Paul], 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 maintainer's 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 a couple, 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. I evaluated Hank's, too, and didn't find any significant performance advantage.

An alternative to the Whitney maintainer can be found in the catalog of Northern Tool and Equipment Co. [nee Northern Hydraulics]. Northern Cat. # 167951-C134 [$19.99 + ship.] is similar in design to the J.C. item. In fact, the Northern maintainer is represented as having reverse-polarity and overload protection. So, for the same price, it should be a better value than J.C.'s. I haven't evaluated Northern's. If anyone has, I would appreciate hearing from you. Northern's number is 800 533 5545. [On line: www.northern-online.com]

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 proximity to 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 A DAYTIME PHONE NUMBER. Also, please be patient, I try to return every phone call, but it sometimes takes awhile. If you don't hear back from me in a few days, try calling again. The best way to contact me is via e-mail.

Copyright 1999 - V. M. Lucariello, PE