Battery Died and I don't know why.

J

jaguar6165

Senior Member
Any ideas the key was off and in my pocket the lights weren't left on. I have a 12 volt system with a radio installed but that was off as well. I drove it to work in the morning and when i left it was dead. I had a noise reducer for the radio so im thinking that was using a very small amount of power but I just don't think it drained the battery considering it sat in the garage the past three days with no charger on it and not being driven and it fired up.
 
could be a short in the wiring or maybe a battery post clamp came off? Happened to me. went over a huge bump and it actually came loose and jump the post. Or perhaps its time to get a new battery. how long have you had it?
 
if your looking for a draw disconnect one of the battery cables at the post of the battery and connect a 12volt testlight from the post to the cable you disconnected. no light at all means no draw. since you have a radio the memory for that can cause it to light very dim which is ok. if it is bright that would be a 12v draw. if you find you have a strong draw just start disconnecting and isolating components until it goes out. that includes the b wire to the alternator

i assumed you made sure its charging when running before you ck for draw
 
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if you are running an alternator it is possible to have one or more shorted diode that will drain the battery yet still put out voltage to charge the battery while driving.

Tom Endy
 
Or maybe your battery has simply reached the end of its useful life. Sometimes you just need a new battery.
 
A week ago I left my overdrive switch on. The next morning the battery was dead. I put my charger on it for a couple of hours and all was well again.
 
The battery is only a month old so it should be ok. I have a one wire altenator which i thought i might have charging problems with but lately if i rev up the engine the amp meter shows im getting a good charge other than everything looks good. I charged it yesterday so ill have to watch it closely and ill check the brake light switch but that is brand new too.
 
Add a disconnect turn it off, if battery goes dead its the battery.if it stays up check for
the problem .First see if you have a spark at the fuse, if you don't have a fuse get one for sure
 
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I have a one wire alternator on my '27 T coupe. If I listen closely after I shut the car off, I can hear a very faint high pitched whine coming from the vicinity of the alternator. Whatever it is, its not strong enough to register as a discharge on the ammeter, but I bet it would discharge the battery if I ignored it. Fortunately the car came with a heavy duty battery shut off switch, so I have never had a dead battery.
 
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