Battery Drainage????????

[itllmakeit]

Anyone have any ideas or input as to why or what would cause a battery to drain? The starter, battery, and alternator have all been tested and they are all good. Alternator has been replaced. At start-up battery has about 10 volts, pull battery cable truck dies. Re-start and give her some gas volts run up to around 14, pull battery cable she stays running. Its as though the rpm's gotta be up there before she starts getting anything through alternator. Battery could sit for days unhooked and keep charge but if kept hooked up, she drains all the juice. I have been searching this problem for some time now and thought I found it when I discovered my positive lead had melted on the headers but no luck. Funny thing is that my neighbor is having the same problem with his chevy too. Anyone got any answers??

 

[sled_dog]

OK is that 10Vs while cranking? If so that is very normal.

If you have one, hook an ammeter in series with the positive cable on your battery(careful doing this as you can cause a spike and blow out a meter). If you have amperage draw of more then say a few mA then you have a parasitic draw somewhere. Start pulling fuses to narrow it down. Whenever the draw goes away, you know what circuit to look at. Then trace that circuit(likely need a schematic for that) and find your problem.

Alternators don't put out a lot of Amperage at idle(say maybe 20A), but voltage should come up to 14V unless battery is low. Could be a dead battery. Got an AutoZone and have them test it out(after charging it up to about 12V).

 

[dyeager535]

BTW, pulling the batt cable while it's running is a good way to kill your alternator.

 

[xblaxermnx]

I have about .01 mA, and I dont drive my Blazer but once a week, will this be enough of a draw to cause a problem? Or should I chase the draw. Once I unplugged the 2 wire connector off the back of the alt, the draw went away. Just tired of jump starting this darn thing

 

[1985_K5_Silverado]

My quartz clock puts a miniscule load on the battery, though it'd probably take a year or two to make a dent. I suppose a stereo's digital clock would be even less of a load.

Anyway, as was suggested, run by autozone or a similar place that does free testing.

"AutoZone will test your car's parts for free. We can test your car's battery, alternator, starter and voltage regulator while they're still on your car. "

 

[diesel4me]

Alternator not charging..

It sounds like your alternator isn't charging all the time,if it only starts charging after starting it up and revving up the engine!..this can be caused by no voltage to the white or tan wire at the 2 prong plug on the alternator when the key is turned on..use a test light,with the motor running there should be 12V at BOTH wires on the plug..check several times,since your problem sounds intermittent..

I had this very dilema on my 74 K20,a former owner puts in a "custom" aluminum dash with gauges,and leaves the curcuit board plug from the original dash taped up and hanging under the dash!..this of course left the "ALT" light,and the 12V power wire that went to the alternator "dead",so it would not "kick in" and start charging until I'd rev it above 2500 rpms..dont ask me where the alternator got its voltage from,but it would kick on rather suddenly,and it couldn't have been good for the diodes and regulator..

Once I ran a new 12V hot wire to the alternator plug(hot only with ignition "ON",with a #194 bulb in series with the wire,for resistance needed to charge properly) it charged normally again,and my battery didn't croak like it did before ..

I was getting tired of begging someone to jump start me after I'd leave my yard and drive 10 miles..it always started when cold,but once the motor warmed up,the battery was too weak!..I noticed if I drove slowly or in heavy traffic,my voltmeter never rose abouve 12V!..that was the tip off,once I found out it was not charging until I hit 2500 rpm's or more,I made sure to rev it that high after I started it in the morning..but fixed it right when I decided that wasn't the best for a cold engine!..

 

[AZ79K5Project]

Do you have an aftermarket radio or amp? Both these units have full time power for different purposes. With the power off the drain should be almost zero. I have seen one ignition switch not turning off properly. The ignition stayed in the accessory position and was sending power through the system.

I agree with the ammeter in line. You do have a drain somewhere.

 

[RootBreaker]

did you add any electrical device lately? anything.... even if it was a cell car charger......



I upgraded to the factory tach and could never figure out why my truck would die in a week.. well the power to the tach was in the bat location and not ignition.... so there was my drain...

 

[xblaxermnx]

So .01mA draw is a problem?

*sigh*

I did add an aftermarket tach and a few amps. I will disconect the amp main power lead and check that. Also I will disconect the tach and check back

 

[Skigirl]

.01 mA is not too much of a draw. You sure it's not 10 mA? IIRC (I chased a battery drain for months a few years ago), up to a 20 mA drain was pretty typical with car stereo and clock and wasn't usually a problem. If you're driving it once a week and the battery is recharging, i'd think it was something else, unless you don't drive it enough during those outings to recharge the battery.

I went ahead and put in a battery disconnect so I wouldn't need to worry about whether I put something in that drained the battery. Ran it into my cab so it's easy to turn on anf off.

 

[xblaxermnx]

Heres the situtation, I think.


Bad grounds, coupled with weak ALT, and parasitic draw (Newly installed stereo amps )= dead battery.

Added a couple of ground strapps, frame to block,body to frame, bat to body, and wire brush all ground contact points, new OPTIMA battery, and ALT= 14.5vdc at the positive terminal on battery!

Thanks for all your help, I still have a .01mA draw, but when I unplug the 2 wire connecter from the back of the alternator and the draw goes away.

 

[diesel4me]

It could be one or two of the diodes in the diode trio in the alternator is bad..this will allow it to "back feed" current to ground,also it will reduce its total output..but might not set off the "ALT" light,or show up as low readings on a voltmeter,since its amps your lacking,not voltage..