TAmes

Hi all,

I've been having an unusual issue lately. I use a battery tender (I have the Battery Tender Plus: ) about once a month, since I drive only about 10 miles/day, usually in the city. After disconnecting the battery tender, either the first or second time I start my car, I'll receive a "high battery drain" warning, which goes away after I next start the car.

Any ideas as to what might be causing this? I posted recently about taking my car in to the dealer to have its battery checked out, and my SA performed a full energy diagnosis of my car, including testing all of the electronic modules. Everything was performing fine, i.e., shutting off properly when the car is asleep.

I'm puzzled as to why I'd get this warning consistently immediately after charging the battery. One thought I had is that this might be related to the fact that I don't immediately disconnect the tender when the charge is complete -- sometimes the charge completes in the middle of the night -- so perhaps the battery is draining between when the charge completes and when I disconnect the tender?

Appreciate any thoughts.

-TA

gerrypd

I attach a battery tender to my car every weekends since I do drive my car 12 miles a day as well. Leaving it plugged when it is fully charged doesn't matter. The battery tender has floater that keeps your battery at 12V and automatically shuts off when it reaches that point.

There's got to be something else that is draining your battery.

TAmes

Thanks for the reply. Sounds like I'm in for another trip to the dealer to check out the issue...

tta197

My 08 535i does the same thing with my battery tender. Took it in to get checked and they nothing wrong. When I mentioned that I use a battery tender, the technician told to stop using it.
It screws with computer. I've stopped using and have had no issues.

TAmes

That's interesting. Thanks for the feedback. Between having a screwy error message and having a dead battery, I guess I'd prefer to have the error message...

vern

Make sure your car is going into the sleep mode. You can check it yourself, my car only takes 5 minutes or less to go into the sleep mode and I would think your car would be in the same time frame. Just look inside the car at the console and where the window controls are on the drivers side door and make sure the led lights are out if they are not out your not in the sleep mode. They have found out in some cases if additions have been installed into the car and not hooked up right the car will not go into the sleep mode. Good luck
cheers
vern

Rudy

I think the best way to confirm that the car is asleep is to look at the start/stop button. If it's illuminated, the car is awake. On cars without start/stop buttons, you can look at the "P" indicator on the shifter. On manual cars without a start/stop button, I really am not sure...

TAmes

Vern, Rudy thanks for the suggestion -- good idea to confirm that my car is actually sleeping.

vern

Sorry when my car is not in the sleep mode the start/stop is not illumiated.
cheers
vern

xyzbird

My 545 had the high battery drain problem when I bought it second hand over a year ago and the battery was replaced. With low mileage I decided that a regular weekly charge would be advisable. I purchased a Black & Decker BDV1084 (UK Spec) 2/6/10 amp Fully Automatic Electronic Battery Charger and have had no problems in the year since. I only use it at the 2 amp setting and it takes about 3 hours before it switches to standby - it will come on again from time to time to make up. The car sometimes is still 'awake' (but goes to sleep in about 20 minutes) whilst charging. Providing you make sure to connect and disconnect whilst unpowered there shouldn't be a problem.