Battery chargers

Years ago, charging motorcycle batteries was a hit-or-miss proposition. You could not leave a charger hooked up indefinitely or you would cause the battery acid mixture to evaporate, ruining the battery.

All this changed with the introduction of the automatic BMW battery charger, and later by the introduction of the popular Battery Tender. Now, you can connect this charger to your battery and forget it. Fully automatic, the Battery Tender will bring a battery up to full charge and keep it there, without damaging the battery or evaporating the fluid. I keep my motorcycle batteries on a Battery Tender for six months or more and they fire the bike up right away with perfectly charged and undamaged batteries.

Battery Tenders are available in several voltages, including the common 12-volt variety (above, left) and, for owers of pre-1970 BMWs, the 6-volt version (above, right). The list price of a Battery Tender is about $60, but they can be purchased for about $40 from discount motorcycle suppliers, such as Competition Accessories. Check the prices in any monthly motorcycle magazine or in BMW Owners News for the best deals and for toll-free "800" telephone numbers.

Another technique I have used successfully for long-term battery storage is to remove the fully charged battery from the motorcycle, put it into a plastic bag and seal the bag, and place the battery in a refrigerator. When I remove it from the refrigerator months later, the battery has all its fluid in place. It just needs a little Battery Tender charging and it is ready to go.

Chargers for 2004 models. The charger above is marketed by BMW itself for the new 2004 series motorcycles with gel cell batteries.

According to a March 2003 memo to BMW dealers from BMW of North America, “The gel cell battery requires a different battery charger than the lead acid battery. This is due to the properties of the gel cell itself and detailed information on this subject will be released in a coming [service bulletin]. NOTE: if a standard battery charger is used it is imperative that the battery be isolated from the bike's electrical system as the potential exists for terminal damage to the control unit.”

The new BMW battery charger for gel-cell batteries came on the market in May 2003. It is BMW part number 72 60 7 679 940. Retail price is a hefty $115. With respect to this charger, BMW states, “There is currently only one battery charger approved for use when charging or maintaining a gel battery through the BMW accessory power socket.” [Service Bulletin 61 002 03 (007), April 2003]