battery drains

[jwclem1]

I have a 1985 K10 4x4 5.7L 350, Truck has been working fine and starting fine. Went out to start it one morning and it clicked a real fast steady clicking like a low bateery. I turned key back to off and waited and tried it again and held it in crank position and it started cranking slow and started. I let it run for 15 minutes and drove it for 15 minutes. I stopped at hardware store and was inside for 20 minutes. I came out and engine barley cranked over and i waited for 15 minutes and finaly cranked over enough to start. i took truck home and charged both batteries. I took truck to Advance Auto Parts and they check batteries, Alt. and starter. Starter had a high draw so we replaced it and retested and tested good. The guy went through a 2nd complete test of every thing and tested fine. I drove truck home and it sat for about 40 minutes and I tried starting it. Guess what cranked over slow and not enough to start it up. I charged both batteries and the guy came and load tested them and tested fine. I let it set over night and same problem this morning. Any one have and ideas or have heard of this? I need help. By the way it has the 2 battery system because I have a 2 year old Hiniker snow plow for it. Never had a problem with it before with old plow or new plow. Any help would be great.

[VileZambonie]

I'm assuming your batteries are connected in parallel with good clean connections. Do you have a volt meter? Do you know how to performa voltage drop test?

What was the current draw while cranking?

What is the condition of the batteries? Were they isolated when you load tested them? What did you test the batteries at? Did you do a standard 15 second carbon pile load test at 1/2 CCA? What is the charging system output Voltage/Amperage?

[jwclem1]

Not sure if i still have the read out sheets from Advance Auto parts. both batteries are 3 years old. Alternator is 1 year old and is heavy duty,  I do have a volt meter. All the test where done off there machine. I have never done a drop test before.

[VileZambonie]

Batteries 3 years old and alternators a year old really means nothing. In order to help you, you'll either need to do pinpoint tests, get those results or have it looked at by a qualified tech.

[Jason S]

Have you checked the alternator?

Are there any solenoids, etc from the plow or any other accessories (Radio, Amp, etc) that you can disconnect from the system?  If you were to isolate a component then you'd find your drain. 

[454Man]

I've found the easiest way for me to find a source for a battery being drained is to do a continuity test. With the battery disconnected. Connect the positive lead of the voltmeter to the positive battery terminal then the negative to a ground. After that start disconnecting things and watch the voltmeter. You will know when you found it.

[jaredts]

I've found the easiest way for me to find a source for a battery being drained is to do a continuity test. With the battery disconnected. Connect the positive lead of the voltmeter to the positive battery terminal then the negative to a ground. After that start disconnecting things and watch the voltmeter. You will know when you found it.

I'm not sure I understand what you're saying on this check.  To check for a draw, I would pull off the negative cable from the battery and put a multimeter's probe on the cable and the other on the battery post.  Make sure that one meter's cable is in the common and one on the fused connection on the meter and put it on dc amps.  As you pull fuses from the fusebox or disconnect suspect connections you should see the amps being pulled go down.  There should be a voltmeter in your truck's dash, but you haven't mentioned what you see there while driving and just before cranking.  Might just be corrosion in your battery post connectors or a bad ground connection.

[454Man]

If there is a draw on the system there will be a connection between positve and negative somewhere in the system, so by connecting the positive lead of the volt meter to the pos battery cable and the neg to the neg if there is a connection you will get a numerical reading on the volt meter

[454Man]

The symbol with the arrow is the setting needed to perform this check. Or just use the ohm setting. Either way the results are the same

[jaredts]

Just read your post again, I misunderstood the first time.  Amp draw just seems more straight forward to me.  I'll experiment with your way sometime.

[Avidyn]

I'm with jaredts. By far the easiest and most reliable way to find a short. Keep in mind, most vehicles will have somewhere around a 0.5 amp draw on the system. This is normal. But, anything over that can cause battery drain issues. We dealt with these problems at least twice a week when I helped run Ed's Auto-Lectric. Watch your meter while you unplug fuses and you'll find find your culprit.

[rsandusky]

I'm with Vile. The batteries need to be disconnected, charged and tested independently. A problem in one battery could masked by the other battery. A 0.5 amp draw is normal but two batteries drained in 40 minutes would suggest a bad battery or a larger draw that could possibly blow the fuse in the meter. A clamp on ammeter would be ideal for testing in this case.