Alternators are known to drain batteries.

have your alt checked out

also, For one or 2 nights ..just disconnect the battery (both cables) and see if it discharges on its own.....as they can do that too.
sometimes they short out from vented battery condensation being on the top of the battery.
make sure it is clean and dry.

I am pretty sure your battery is fine and you have a charging/alternator problem.

4 days is about right for an engine/truck to drain a battery.
Once the battery gets to 5 volts or so the ignition quits.,

 

Know someone with a meter?
How old was your old battery?

I just traded in a good battery and got some money back on it. :)
It was an Exide from Checker, the sucker just wouldn't quit eatin up my pickup.
Bought a new one from AutoZone, so far so good. :)
Bought two actually while I was at it. ;)

My daughter in law's van wouldn't start.
The voltage on the battery was low, ~10 volts.
Dropped to like 6 volts or so while the starter was engaged.
The cables etc were prob'ly fine, since the voltage dropped.
I jumped it.

The voltage climbed to ~14 while it was running.
So the charging circuit is working fine. :)
Let it run for about 10 minutes.

Killed it, started it and the voltage dropped, while cranking the starter, down to 10 volts. Not so good, maybe not charged back up good enough?
Prob'ly a weak battery.

Again, the voltage climbed to ~14 while it was running and let it run for a while.
Shut it off. Went in and wasted some time. :)

Came back and it wouldn't start, the voltage dropped to about 8 while the starter was engaged.

Went to AutoZone and bought her a new battery and myself one while I was at it. :)

If the voltage hadn't risen to 13+ while running after the jump, the battery could have still been weak see? But for sure, if the voltage doesn't climb to 13+ volts the charging circuit is bad. If that's the case, then fixing that should be done first, then see how the battery responds.

As far as figuring out whether it's the voltage regulator or the alternator, I don't know how to do that with a volt meter. Anybody know off hand? :)

There's something about the alternator "not making a magnet" when the engine's running is a sure(?) sign the alternator is bad?

Anyway, I've always had spares on hand.

I've had one bad voltage regulator and this goes back to the early 70's and old VWs and dune buggies and dirt bikes and all sorts of other junk. :)

I've adjusted them down so the charge wasn't so high and I've had them where the contacts needed cleaning, the charging voltage was out of sync with the contact sound. Only one I can remember i couldn't get working, it was a 12 volt Bosch regulator on a air cooled VW based dune buggy.

With the new electronic ones, all that fun is gone? ;)

BTW, a meter will pay for itself in time and money.

Also, IME batteries tend to slowly fade away, until they get near the end of their "life" then they act fine and act dead and act fine and act dead.

A volt meter ain't fooled by that crap. ;)

I've had batteries, I knew were bad, on the company truck and left it for the battery to be changed to come back to get it and they instead...

"tested the battery and it's fine (you don't know what you're doing)"
"wanna friggin bet money on that battery?:)"

Had guys at Sears would pull that on me when I'd bring in DieHard batteries.
Refuse to give me a new one. :/ I didn't live in town danggit.
Had that happen to me twice and the battery would be dead in one or two days.
Checker pulled that on me once.
I got to where I pour half the acid out and replace it with water so it'd for sure test dead, just in case I ran into one of those guys that insists on testing it.

They want to play games?
Turn about's fair play. :)

This last time tho, I told them the battery is still good, but it leaks out the top and I was tired of it. :/ Also told them I used to maintain lead/acid Exide batteries for a living and they were good suckers, what happened?
They forget how to make a good battery? ;)

Alvin in AZ

 

I don't know if you'll check on here before I call you, but I'll bring my multimeter and test light down when I come to check out the tires tomorrow. I just went through the same problems with my truck. We can find if you have a drain or if your alternator is just bad.

 

Cool! :)

Let us know what you find out ...and how you figured it out? :)

Alvin stupid as a rock in AZ but knows how to use a meter :)

 

Well, started the truck up, and the alternator was charging fine.
Ran a test light between the ground strap and battery negative. And there was a drain. Pulled all the fuses, and the light didn't go out, but started pulsing, like turn signal speed. Which was just bizarre. Pulled both the flashers, still no change. Patrick noticed a buzzing in the cab, which was going at the same rate as the light. Traced it to the stereo. The direct power for the stereo was hooked up to the positive battery strap, pulled that wire, drain was gone.
It's a really nice new stereo, anyone here have any idea what would be installed in a stereo, that would cause a pulsing power drain while it's off? Maybe some sort of alarm or sleep mode or something?

By the way Patrick, your truck might be a beater on the outside (Still, gotta love the Mad Max trucks ), but that interior is AWESOME. Hope to get mine looking that good someday. You should get some pics up in your gallery at some point... See you tomorrow man.