DaFunk_80

Hey everyone.. Hoping someone can advise me on this before I take the car to the dealer to get ripped off !

Past few days, I've been noticing that my CLS was getting less and less cranking power from the battery. I left the car parked for one day, came back, and the battery was dead.

Put a voltmeter on it, and it was at 8 volts at the time. Boosted the car, and I was getting a healthy 14.21 Volts. Let it run for 15 mins. Shut it off. Checked the battery again, and it was at around 13.50 volts. BUT THEN: I leave the voltmeter on it, (Car is still off) and notice that every 30 seconds the voltage deccreases by 0.01 volts! After 5 mins or so it decreased by 0.10 volts! Is something draining my battery? I made sure everything was off.. How do I troubleshoot this??

I bought the car used, and its got a strange battry I've never heard of.. Starts with a D.. not delco, but something like that.. Anyway the battery is probably old, but there's still a green light on in that little see thru round thing.

FINAL Note! : My right HID headlight went out a month ago.. been driving without it.. looked at the headlight fuses one day. They looked fine. Looked at them again today, and the right fuse was blown! So I pop in a new fuse.. turn on headlight (car off) and it blows again! Could this be related?? THANKS for the help guys....

Allout

You can run your test after you isolate the battery. Charge up the battery and then pull the ground off of the battery. Check the battery with your Volt meter again and see if you still get the same voltage drop. My guess is that it still will and that you just have a bad battery.

The headlight could be related but I don't think it's likely.

lcstyle

if your car is reading 14.21 volts measured while the car is running across the battery terminals this means the charging system is functioning properly. Your battery probably has a dead cell or cells, replace battery. good to go.

there will be a minimal draw measured on your volt meter on the battery while the car is off, but its always a minimal amount < .5 volt due to aftermarket accessories and clock, etc etc.


BTW, disconnecting the negative battery terminal to see if the car dies is an old school trick used to isolate the alternator as the culprit, but in modern automotive systems this could spike the alternators regulator and burn it, or burn some other sensitive engine electronics (ie. FI computer) etc. so its not a good idea to do this.

laters.

lcstyle

oops, forgot to read this part, its obvious to me that there is a short in the wiring somewhere or there is a component somewhere in this wiring that is grounding itself short circuiting.

This could cause significant drain on the battery, until the fuse blows. It's likely that you may just need to inspect your wiring because a short circuit will cause significant drain on the battery and possibly a fire due to overheating wires, your lucky you have fuses installed, the fuse blowing is telling you that there is something wrong here. Fix this problem first, then see if the existing battery will hold a charge by having it tested at a local automotive shop after a full slow charging.

lcstyle

one last thing, to measure actual battery draw, you must connect your voltmeter in series to one of the battery terminals by disconnecting the negative cable and using one lead to connect to the cable and one to the actual battery terminal, otherwise you will only be measuring battery voltage.