How Do I Maintain My BMW Battery?

Tips & Support
OPTIMA Batteries
Milwaukee, WI

Every battery OPTIMA sells includes our 800 number (888-8-OPTIMA) and our e-mail address ( but some folks prefer to have their questions answered here in the Power Source blog. Today's first question comes from another Jim, who asks,

I have two YELLOWTOP batteries in my 1993 BMW 850 Ci that require charging while the car is not being driven to keep the computer active. Is it best to storage charge each battery separately or in parallel together as one? 

If the batteries are wired in parallel, as is typically the case in many diesel truck applications, they will both receive a charge, even if the charger is only connected to one of the batteries.

Larry asks, Do gel batteries gas? Can you charge them in a closed area?

All OPTIMA batteries are AGM (absorbed glass mat) lead-acid batteries in a SPIRALCELL design, not gel batteries, although we assume you are referring to OPTIMA products, since you did ask us the question. All lead-acid batteries can vent gas that is both flammable and toxic in extreme situations. For that reason, we always recommend that batteries be installed in vehicles in a manner that allows any gas to escape to the outside air. This is especially true for any battery located in an enclosed area. This can be accomplished by using the vent tubes that some OPTIMA products are equipped with (Groups 27, 31, 78, 51, 34C DS46B24R, DH5, DH6, DH7) or by installing a battery in a sealed battery box with venting provisions to the outside air.