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Ron K

E46 M3 battery drain

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Hi guys, did a quick search, nothing came up.

So my e46 likes to drain out in 3-4 days of no usage which could be just the battery being old (will check later). If I drive it more regularly and not leave it sitting for more than 3 days I have no issues with the battery. i.e. it does charge and all.

But before I go and buy a new battery, is there a recommended electrician that could see if there's any drainage/short/whatever else? Ideally in North Shore or CBD.

Also any recommended retailers for batteries, if there is one other than the usual repco/bnt types?

Thanks!

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How old is the battery? If you can, get the battery tested and see if it is ok. It may need a full charge on a charger or it is poked and needs a replacement.

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Will ring tomorrow if I can :)

Checked the manufacture date.. and it was the same as the car :D So I might actually look around for a replacement.

Any recommendations?

Also, I tried to look for those caps to check the fluid level and it seems it's not designed to be accessible, as in the cover over the caps doesn't come off. Can someone confirm?

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Probably the battery...but if you have installed anything that gets power from the rear lighting circuits (LEDS or reversing camera) it is easy to provide an unwanted return path that drains the battery very quickly.

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Ron

At the top end for batteries look the BMW AGM factory batteries are the way to go if you are keeping the car for a long time. They were original used with the e38s due to their high drain electrical systems. The AGMs are better at holding a charge and will recover better from a near full discharge than most other types if your car sits around a bit.

Down side is they are closer to $500

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The CSL used a smaller, lighter battery (480CCA?) so you could save a couple of bucks and grams with that.

My M3's battery also last about 10 years.

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On a similar note, is anything left plugged into the cigarette lighter?

I've noticed that my radar detector doesn't turn off when the car goes to sleep.

Edited by DarrenG

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A simple load test will give you all the answers about the battery's health.

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