Battery dies overnight?

[schmidty]

Every morning when it's really cold the night before my battery seems to die.
It didn't seem to be a problem in the warmer months. The only thing 'on' using any power is the little power light on the radar detector and the flashing light for my keyless entry.

Battery and alternator check out fine. Could the cold be causing my battery to drain? or could condensation on the terminals cause problems? Could there be a 'leak' somewhere?

I'm going to disconnect my batter tonight and see if its still dead in the mornin.

TIA for any help of suggestions
Ryan

[jlevie]

The possibilities are; the battery is old and has diminished capacity, or there's excessive parasitic loss. If the battery is over four years old it may well be on its last legs and just not up to the higher starting loads from colder weather. Or something could be drawing too much current when the car is idle. Normal parasitic draw should be pretty low, something less than 100ma. Improperly installed aftermarket audio and alarms are frequent causes of excessive parasitic draw.

To check parasitic draw one interposes and meter in the negative lead from the battery. Best to do this with an autoranging digital meter. If you find excessive current draw you pull fuses one at a time until you find the offending circuit. Then it becomes a matter of examining each item powered by that circuit.

[mikeedler]

if it is only when it is cold, just go buy a new one.

[AdironRider]

Yeah sounds like its new battery time. Ive heard good things about Optima red tops.

[euroshark]

Make sure the terminals are CLEAN. My Alfa had a chronic problem with corrosion in between the terminals and the connecting pieces... It was barely noticeable just by looking. Caused more than a few headaches. Maybe get some gold battery connectors, they are available from pretty much any automotive store, and they kick ass!

[schmidty]

well, i had the battery tested and they said it was ok. Maybe Ill get it checked again somewhere else.

...but now I have possibly another problem. Being the expert electrician that I am (*see sarcasm), I took a look at my keyless entry and stereo to check the wiring. I noticed a loose wire and reconnected it and then clipped another that wasnt needed... Now my stereo doesnt come on and the car doesnt crank/start. Checked the fuses and they are ok and I dont think the battery has drained again because other funtions like the keyless entry and interior lights still work!

[jlevie]

Undo what you just did, check all of the fuses (as in with an ohmmeter), and see if the car will crank. And while you are at it check the battery voltage. If it is fully charged it will read 12.7v, and at 25% charge it will read 12.0v.

[schmidty]

Undo what you just did, check all of the fuses (as in with an ohmmeter), and see if the car will crank. And while you are at it check the battery voltage. If it is fully charged it will read 12.7v, and at 25% charge it will read 12.0v.

thanks...I disconnected the headunit all together and disconnected the battery for now. I need to get my hands on an ohmmeter to test everything.

[jlevie]

Radio Shack and other places have resonably priced digital DMM's. If you are gonna fool around with an E30 (or any other car) a decent meter is just about indespensible.

[DaN]

The radar detector shouldn't be left on, they can draw about 200mA and drain the battery.