Electrical problems, woes, issues, et al.

So I go to start my truck project tonight and it SLOOOOOOOOOOOOWLY cranks, and finally just doesn't turn over anymore. Break out the battery charger, stick it on a battery, and watch 6 amps getting pumped in. I let that run for a hour or so and it is still sucking down 6 amps. So out comes the test light and voltmeter. Test light shows all the proper places getting 12v and those that don't, ain't. Take the voltmeter to both batteries and one is 12.0v and the other is 11.7v. Nothing too unusual for drained diesel batteries, IME. Voltage drop off the ground cable to battery post: zip, zero, zilch, nadda. Already tested the alternator a few weeks ago and it tests out fine because of the battery light being on. Batteries are 2mo old Deka's.

Could it be the starter? Bad battery or pair of batteries?

double checked all connections, including ground?

Yes, and yes, but the chances of the car gods dumping on you that bad in succession is extremely low...

12.0 volts is dead and 11.7 volts is deader than dead. You need new batteries. Replace them in pairs after you have given them an overnight charge and load tested to confirm their deadness again. Are they older than four or five years?

In reply to rodrammage:

2 maybe 3 MONTH old batteries. Always replaced them previously in pairs.

In reply to Raze:

Yes, all connections are tight.

How long did it sit? Could it be a drain of some sort sucking the batteries down?

Fully charged batteries should read 12.9-13.2 volts. Check your charger and re-test them? Then go look for a draw in the vehicle's electrical system to see why they were dead after only 2 months of sitting. Even modern high end cars with all their electronic doodads can sit dormant for 2 months and still start in the warmer temperatures. What do you mean when you say that the battery light was on a few weeks ago? Care to expand on the history of the episode regarding that light?

Those batteries should be under warranty.

Make sure you don't have a draw on the system before you go in for warranty.

Shawn

Batteries were just installed in the past few months brand new. Battery light came on after it had been running for a few minutes about a week ago. First time is has EVER been on. Alternator tests out fine after being replaced last summer because the other was seized up. Stopped at the starter shop just a little bit ago, the batteries and starter check out OK.

Draws, don't have any if my testing is correct. Both battery grounds unhooked and ammeter in between one of the ground cables and (-) post. Both batteries show zero amp draw.

So, I am unclear if you have attempted to start the vehicle with batteries that are reading 13 volts prior to cranking or if you have attempted to start the vehicle with batteries that only have readings between 11.7 volts and 12.0 volts. What happens if you try to start it with batteries that read 13.0 volts prior to cranking? Did it still crank SLOOOOOOOOOOOOWLY?

Reading 13v, starts great. Don't know when they are below that until you start to crank, since it ran just fine a week ago.

Light on, alternator not puting juice into the batteries.

Ok, so the batteries load test fine, the starter works (when the batteries are charged) and the engine isn't obviously seized since it starts and runs. So, there must be a reason why you have a condition that presents dead batteries. Two reasons for this are: the vehicle's charging system isn't charging them when it is running, or, the vehicle has a draw that discharges the batteries when it is not running.

Since you have no draw (most cars draw a few milliamps when off) and since you had an alternator light come on recently, you might want to sniff in the direction of your charging system. What does your DVOM read at the battery terminals when the vehicle is running? It should be up around 13 volts and not steadily dropping, even if you switch on heater fans, lights, etc.

I musta fixed it through doing everything twice.

First off I started cleaning off the terminals on the starter and fender mounted solenoid and...... broke a stud off necessitating replacement. Oops.

Reinstalled starter and left the batteries out to charge. I unhooked them when they reached 2 amps charge rate. Both batteries showed 12.9xV after sitting a few hours after charging which took all night. Installed the batteries back into their trays and hooked up the cables. Got it started and had the battery light on for a few seconds and then it went off.

Anyways here are the readings after it had been running for a few minutes, AKA- how long it took me to hook up my meter.

Left (driver side) battery:

Right (passenger side) battery:

Straight out off the alternator:

I guess for now, it is "fixed". Thanks for all the help!