Battery going dead 2001 BMW 330i

Whenever a car has this type of a problem, it is normally because of poor connections, belt slippage *severe*, or - very possibly, something is putting an excessive drain on the battery when it is not running.

My experiences have been to first check that ALL the connections are totally clean - especially check your battery posts and make sure they are tight with very good - surface-to-surface contact. Remove BOTH connectors on the posts and clean with battery post cleaning tool *wire brush* and then use the spray that stops / limits corrosion.

Are you sure that battery IS OK? Take it in for a load test - old batteries often deteriorate over time *sealed or not* and it just might be time for a new one. Get the biggest 1 that will fit in where it is held. More amperage *rating* is always better.

Poor connections often happen during cold weather season *expansion and contraction cause this*.

BAck to connections again - VISUALLY inspect ALL your cables/wires for discoloration. Connections need to be tight - end-to-end in the charging system. I am not sure if the car has a starting relay or not - and if so - where it IS located. THAT TOO is a problematic area due to poor connections that quite often, just may need to be cleaned.

Are you sure your alternator IS good --- are it's belt nice and tight- but not too tight? Speaking of the belt ... look on the inside track of the belt - has it been replaced recently or is the rubber in poor shape *splits, showing sign of extreme heat from slipping etc*. When you have a load test - that test alone will indicate whether it IS charging even if everything is running like A/C, radio, light, wipers. Check you gauge inside the car - IF it has one - and no matter what RPM ~ it should still be charging *showing positive charging - NOT discharging*. Lastly - the alternator OUTPUT -- is it the right one for that car - correct rating???

There are even more areas worthwhile checking ... but unless you have the correct tools and diagnostic equipment - it can be tough to nail-down the right specific problem. A lot of places *like Sears* will have that - and used to not charge for the diagnostic - because they wanted to sell you THEIR battery.

One more thing .... most cars will have some minor drain due to clocks running, alarm working and so on. HOWEVER - if a light *like an interior or truck light* remains on, that will give you a larger drain.

A battery should never go dead while driving - and your light *running lights* should always be bright .. are yours??????

Hope this helps!