Hi my first visitI have been having problems with battery drains lately. Overnight the voltage of my car battery drops from 12.4 to 11.8 and if I leave it more than 3 days it will not start (11.5 to 11.2). On idle and load it is near 14.2. So I feel alternator is charging well.I am about to start pulling fuses to locate drain but was wondering if an alternator that is starting to die (but will still charge) can cause battery drain. Can the diodes in alternators draw current from the battery?Thanks
the surge when shifting into drive sounds like an entirely independent problem. Often this can be caused by low Automatic Transmission Fluid. If it hasn't been run in a while, it takes a second for it to heat up so it fills the torque converter completely. Before it lurches, it probably seems like it's needing to have high RPMs to go a low speed. If it makes a really loud slamming noise, it's possible something in the transmission itself is a problem, but usually it sounds more like grinding, as if the gears didn't quite catch. If the car starts, runs and has 14.x volts on the battery, then your ground isn't a problem. Make sure though you have the actual ground strap grounded to the car. Occasionally the positive cable to the starter is wrapped in black which can lead to problems and a shortly dead battery if you ground it to the chassis. But that's probably not the problem for you. Like other people have said, short circuits can cause a rapid battery drain. If you're leaving it for a week and the battery is dying, I wouldn't worry too much. The car I'm working on right now, (1986 BMW 325e with 1991 525i engine) loses enough power over the course of a week if it's not run so that even the electric locks don't work, much less start. My friend's 1989 325is seems to run dry fast too. Point is, some cars just are big battery wasters and if you don't drive it often, it'll lose its charge surprisingly quickly. Hope I've been helpful, and good luck solving your problem!
Alternator Draining Battery
Yes, it's possible that a marginal diode can cause battery drain. I think your idea of pulling fuses is a good idea. Connect a meter to to the battery to measure current, determine how much draw there is, then start pulling fuses, one at a time. Note that stereos with clocks will always draw some power, as will an alarm system. Be careful what you disconnect, since some alarm systems need a complete reset if power is lost. The ignition / fuel management systems on some vehicles are also affected by power loss. Check your owner's manual first!
This Site Might Help You. RE: Can Alternator Cause Battery Drain? Hi my first visit I have been having problems with battery drains lately. Overnight the voltage of my car battery drops from 12.4 to 11.8 and if I leave it more than 3 days it will not start (11.5 to 11.2). On idle and load it is near 14.2. So I feel alternator is charging well. I am
full charged battery's are 12.4- and up not 13.8 only, that guy sounds like a rude know it all. and yes it can, there are allot of thing inside the alternator that can go bad and drain the battery. if you want to do it the easy way get it tested at an auto parts store, they can tell you. if you would rather do it your self, use to volt meter and pulling fuses, but I suggest putting it on the amps setting and use and use the ground post and terminal. because if you accidentally ground out the positive side you could blow fuses, cause shorts, other kinds of damage, or get shocked. but of you ground the ground. well you'r grounding a ground and nothing happens lol. and don't let people tell you that you have to go to collage to change it or rebuild it. if you look the info up and just put you'r head into it there is no reason you can't do it or at least try. people that tell you that are just smart mouths and the world is full of them. my brother didn't go to school to weld and he is the best welder in this town and my uncle is a very respected mechanic and he didn't go to school for that either. I'm the first man to go the collage in my family and i still have to ask the older people around for advice allot. all school is, is a way to get a peace of paper, take it from me, there was some people in my class that would do more damage then they fixed. and they graduated too. anyways Hope you get it fixed.
