Grand daughters car battery

37chief

Well-known Member
Location
California
My grand daughters car battery goes dead after a few days. It is a new battery probably 3 months old. I disconnected the battery ground, and tuched the post with the cable end, and noticed a very small spark. I disconnected the alternator wires, and it still has the small spark. That eliminates any problem there. Should anything be drawing on the battery when everything is off? Thanks for any help. Stan
 
With all the electronics on today's cars looking for a spark when connection the battery will not tell you much. With multiple computers, each one may do a self check when first connected to power and then power down to almost no draw until the key switch is turned on.

I once worked on a 2004 GMC that would have a dead battery every Monday morning after not being used over the weekend. It turned out to be the instrument cluster stayed in the test mode instead of standby. It was supposed to draw about .5 amps when the key switch was first turned on and then drop to a few milliamps after about 30 seconds. To find the problem I connected a ammeter between the battery connection and the fuse panel and then started pulling fuses one at a time to see which one had the major draw. There were several that had quite a draw when first installed but then dropped off when the self check was done. The fuse that powered the instrument cluster and several other things would not power down. It was then a matter of disconnecting the other components powered by that fuse one at a time until the problem was found.
 
I have a 1987 GMC van and a 1991 Chevrolet truck that both would have the same problem, it wou take a week to drain the battery. I removed the radio fuse on both of them and that solved the problem. It would be worth a try.
Bill
 
If you can't find the voltage draining problem, I would install a master switch in the negative cable at the battery. This will isolate the battery from being grounded. Show the granddaughter how to turn on and off the switch.
The military has used this for years. Hal
 
I use to run in to this from time to time on cars check the light in the glove compartment some times they stay on and kill the battery in a couple days
 
Any car made in the past twenty years will have a LOT of battery drain when everything is "turned off". The various microcontrollers for the engine, transmission, radio, A/C, etc. all use a little current to stay alive. I would first check and make sure the alternator is putting out enough voltage to properly charge the battery. Then I would try monitoring the current draw with an ammeter while pulling fuses. There shouldn't be any load pulling more than a few milliamps when everything is shut off.
 
Hook up a amp meter in series on the negative post of battery. Let sit for a least ten minutes.
You want around 50 milliamps or less. It must be more if the battery is going dead. Then start pulling fuses to see which one if any lower draw.

Is the key being left in the ignition?
 
If the cigaret lighters/power ports are still on when the key is off don't forget that anything left plugged into them can still be using current. GPS, radar detector, cell phone chargers, ipod, whatever people put in cars now.
 
Did her boyfriend recently install an upgraded sound system?

That was what we found frequently when I was in service management. A young girl would come in with the same complaint, and it would turn out her boyfriend had recently installed an after-market radio--and had wired it so the radio was on all the time.
 
My elderly aunts car was doing the same thing, we finally found she had stuffed.a receipt under the lighted mirror cover on the visor and it was keeping the light on in there.
 
37Chief, over the years, I've found many things that drained by battery. One was the seat belt release on a 2 door caddy. Another was a small lamp in sun visor that turned on when you opened lid to view mirror. Bad alternors. Could be anything.

Best way to find drain is to install an ammeter between battery and one post on battery. Then start pulling fuses.

Have fun.
George
 
Completely disconnect the battery. Now use a 10 or 20 amp trickle battery charger for a power supply. Hook it up to the battery cables and see how many amps are being drawn. This can narrow it down quite quickly.

Things to look for.

Trunk light
Glove box light
Cigarette lighter
Dome light
Map light
Rear window defogger
Heated seats
Amplifier


These are a few things that I have found causing batteries to go dead and a battery charger made it easier for me to find the problem. Most people don't have an amp meter to hook into the system. But with a battery charger it's all in one unit.
 
John, an old school charger will work. The newer chargers require a battery to be connected to before they work. I have both, old school manual and newer smart chargers.

I have many free HF EVOMs. They have a 10 amp scale and a few ma ranges. Everyone should have a voltmeter and learn how to use it.
george
 
Check the radio. My 96 Chevy radio display was staying on and would kill the battery in three days,I found the fuse for the memory and pulled it. The bad thing is, you have to reset the radio every time you shut the truck off,the good thing is it only gets driven to pull a trailer.
 

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