Keeping Battery Charged?

Just use a battery tender.

 

You may have an excessive draw, as a new battery should hold a charge for a week or so. Also, most cars have a slight draw for things like clock, any "keep alive" for ECU or other computers and did anyone install any aftermarket accessories like alarm?

If you cannot use a tender, then you should disconnect the battery via a switch or removing a terminal. That will lose any clock and radios presets at the very least, however.

 

You have a battery draw. Start by performing a draw test with an amp meter in series between the battery and negative terminal, then isolate circuits by pulling fuses until you find the culprit on that circuit. A majority of the time, it is an aftermarket piece causing the draw, such as alarms, stereo equipment, etc.

 

As Mr. parker says just use a battery tender. I use them on all of my cars that do not come with a charger. My experience seems to show they extend the battery life by one maybe two extra years. I had a Battery Tender on my 2013 when I owned it and it worked perfectly.

The aswer to your other question is There is a battery draw on some cars when parked.

They make a battery disconnect sdwitch that you can buy at Autozone or most any other car parts store. It is very easy to install. This makes battery lead disconnect a 1 sec thing to do without tools.

They also make a solar powered battery booster that you can buy.

Batteries do lose power when sitting. Just sitting without any draw they should last for at least three months.

They do make a battery called "Odessey". It is a totally different battery chemistry. I used one in a chopper and a high compression Shelby Cobra kit car. These will last close to 12 months without charge. The big Advantage is the high current power they can provide. This can be important for high compression motors without compression release, so they are hard to crank.

One last thought your M3 is old so you may have an ignition switch problem. This happen on Porsche 011's alot also. This can drain a battery, make certain things not work like AC or just make the car not start.

Those M3's are wonderful cars.

best

Lee

 

As mr. Williams recommends, you can buy a multi meter at any radio shack fairly cheaply.

If you find a current draw I would wiggle the ignition switch to see if you can make the current draw go away. That gives you one data point.

If you find a draw in the lights, the early M3's had a shorting problem in the tail lights. This was with a very early cars it may have been re-engineered with your car year. I do not know.

best

Lee

 

Since I read the entire OP, I won't suggest a battery tender.

There ARE, however, solar maintainers that you might look into if that suits your storage situation. I'd even consider putting the solar panel outside of a shed and running a lead in to the car.

It's possible the new battery wasn't adequately charged for the first go, etc, etc, but the likely issue is that you have a drain and should follow the suggestions here about tracking it down.

 

I missed the part of no place to plug in-- sorry

No reason to go through all that dtuff he recommends although it will work and work well. I bought a solar charger, put it in the windshield and plugged it into the lighter.

I would call battery tender. They have application engineers that can help you. Be sure to have your make,model and year of your car. You need to be sure your lighter is on when the key is off or the battery will not charge. No problem just add the pig tail they give you to the battery then plug it in when sitting.

I am fairly sure as the other poster said it will not recharge a totaly dead battery. But it will keep it from going down. But they can tell you.

FYI I have nothing to do with Battery Tender just a satisfied customer.

Best

lee