billeul

Like many others on this forum my 2004 545i has battery discharge issues. The car has been at the dealer for 3 months over the past four years with out a definite solution.
For peace of mind I have been connecting a battery tender when the car will not be used for more than a day. It is really a shame that we are forced to use a battery tender on a $65K car.
I just wish BMW would step up to the plate and solve their battery issues. Now a question for those who use battery tenders.

After driving 30 or 40 miles, if you immediately connect your battery tender upon turning off the car, does the battery tender show fully charged (green), almost charged (red with flashing green) or charging (red). If it indicates that it is charging (red) how long does it take it change state to almost charged (red with flashing gree) or charged (green). If it does not record fully charged (green)immediately after turning the car off, does that indicate that there is possibly an alternator problem? Answers from your personal experience or theories would be appreciated. Thanks

vkhong

After normal driving, I've connected an intelligent charger to the positive and negative ground posts under the hood. It will not charge.

After short distance driving, the same charger will charge, and will show fully charged eventually. Then it alternates between not charging and fully charge. I assume the E60 has overcharging protection built-in. My E90 exhibits the same behavior.

Other non-BMW vehicles (Lexus, GM) in my household seem to allow the intelligent charger to charge every time, going to fully charged and staying that way in trickle charge mode.

Allen

My car is a '08 535i that stays on a tender until it is driven. I have a Deltran Battery Tender Plus hardwired to the battery going out to a plug. After a drive, when I connect the tender back up to the car, I get a solid red light. After a few hours, it turns red with flashing green, then a few hours later, it turns solid green. I get the exact same response on my 911....it stays on a different tender (same exact model) all the time until it is driven.

billeul

I have the same setup and get the exact same results. Thanks

w5lx

Maybe this "new battery technology" they are using in the new models will help:

BATTERY ENERGY REGENERATION
Make use of every Watt: by charging the battery only when your BMW is braking, coasting or decelerating, Brake Energy Regeneration improves fuel efficiency by up to three percent and ensures that the full power of your engine is available for acceleration.

Today's vehicles require much more electrical energy than older models, due to the much wider array of electric and electronic on-board comfort and safety systems. This energy is created by the generator (also known as the alternator) which converts the engine's power output into electricity. In conventional systems, the generator is permanently driven by a belt connected to the engine.
BMW's Brake Energy Regeneration operates differently: the generator is activated only when you take your foot from the accelerator or apply the brake. The kinetic energy that would otherwise go to waste is now used efficiently, converted into electricity by the generator and stored in the battery.
Producing electricity in this highly efficient way delivers an additional advantage: when you apply the accelerator, the generator is deactivated - so the full power of the engine can be directed to the drive wheels. Brake Energy Regeneration thus increases fuel efficiency while simultaneously enhancing driving dynamics. As a safety precaution, the Brake Energy Regeneration system monitors the level of battery charge and will, if necessary, continue to charge the battery even during acceleration to prevent a complete discharging of the battery.