My 2002 Ford Ranger would not start today. When jumped, it starts fine. Then put on charger and shows 100%. But, the truck wouldn't start on its own afterwards.

Is it possible the battery just doesn't have the umph and needs to be replaced despite showing 100%?

Sure. Have you had the battery tested under load? It's possible it has a decent resting voltage, but it can't provide the current to actually start the vehicle.

bad batteries will often show full voltage when on a charger but as soon as you put a load on them the voltage will fall off a cliff.

If the battery tests good, perhaps the wiring is the culprit. The wiring may pass enough amps to run lights, etc, but not enough for the starter.

Simplest issue is a loose/corroded connection at the terminal. After that, the most common gripe online is a corroded ground.

Yes. It can show full voltage, but be unable to put out enough amps to crank.

A load test at Auto Zone, etc. will detect if the battery is shot or not.

Corrosion under the terminals ?

If the cables are in good conditions and all connections are clean and secure, it's mostl likely severe sulfation in the battery.

A battery in this state may start in warm weather, but after a day or two, or low temps, it will "act like a dead battery". Lights may work brightly as well.

Such a battery needs to be replaced. Usually too far gone to reverse sulfation to a dependable condition.

It's just now getting into winter, and you don't want to be dicking around and find yourself in most miserable weather on the side of a busy freeway in ankle deep slush.

Replace the battery.

quote:

Originally posted by h2oys:
My 2002 Ford Ranger would not start today. When jumped, it starts fine. Then put on charger and shows 100%. But, the truck wouldn't start on its own afterwards.

Is it possible the battery just doesn't have the umph and needs to be replaced despite showing 100%?

Newer chargers will only charge what it think it needs, if it stops taking a charge and is around 12.5v it thinks it's done or 100%.
It's not an indication of the battery condition, for that you need a battery tester.

I have an older charger that dumps 60 amps no matter what, all day long.
If the battery doesn't take a charge then it just gets hot and starts stinking.

I bought a new Ram in late '22, when it got cold 2 months later it began to fail to crank. A test at the auto parts store said it was fine, but I had to jump it about every 3rd time I had to go someplace. I finally said fuck it and put a new battery in it, and haven't any problem since (almost 2 years now).

Stick a volt meter on it and crank it. If it drops way down when cranking, or trying to crank, it's junk. A good battery will drop a little under load (maybe 1-2 volts), but a bad one will typically drop to half or even less.

quote:

Originally posted by 92fstech:
Stick a volt meter on it and crank it. If it drops way down when cranking, or trying to crank, it's junk. A good battery will drop a little under load (maybe 1-2 volts), but a bad one will typically drop to half or even less.

Going to test mine today. It's about 2.5 years old through the heat and cold of west Texas and heat of Florida.

Car wouldn't start yesterday but I jumped it and it started. Started fine this morning. This afternoon it was weak.

I bought from Costco 2.5 years ago and I believe there's some sort of prorated warranty.

Just went through this a week ago. Bike wouldn't start. It tried, but wouldn't catch before it went silent. I waited about an hour, got it started, rode it home and left it running. It was showing 14v. I shut it down, put my multimeter on it, fired it up and it briefly dropped to 7v before catching. I replaced the battery the next day.

quote:

Originally posted by Perception:
Sure. Have you had the battery tested under load? It's possible it has a decent resting voltage, but it can't provide the current to actually start the vehicle.

Bingo. You have a normal surface charge, but voltage is dropping way too low at the starter to do the job. If it works good with jumper cables then you need a new battery. If the battery is more than 3 years old that is probably exactly the problem. The battery has reached end of life, they don't last forever. If both of these are true you may be wasting your time going to the auto parts store for a voltage drop test under load, just replace the battery and you'll be gtg. If you have a better volt meter you can test this yourself, or use a medium priced batter tester, but this again is just wasting your time and money. Buy any name brand battery, like from Sams Club, Walmart, Batter Plus, etc., and install it, and you'll be good for another three years.

Last year this exact same thing happend to one of my old trucks, I didn't pay attention to the age of the battery. The voltage at rest showed 12.something volts, but while cranking my voltmeter showed 9.something volts, which is too low to turn the engine. Popped in a new battery, good to go. As a previous poster replied, replace it now unless you like spending the night on ice in a Walmart parking lot waiting for the tow truck in a bad part of town.

Been there done that.

It was the battery. Bought a new one, froze my fingers off swapping it out, and it fired right up.

When I added the swap to my maintenance log, I figured out the bad one was 9 years old.

That’s a heck of a run for a Walmart ever start battery that cost $100.

Thanks everyone for the advice!!!

Sometimes a starter that’s on its way out will start with the extra amperage provided by the jumper battery. So don’t rule that out. But battery is most likely the culprit. A load test at the parts store will let you know pdq.

Oops I posted before I saw your above reply. It's unbelievable you got nine years on that battery. I'd call that a Sigforum or possibly a world record. Ha !

I have a bright yellow permanent marker and mark my battery month and year when I change them.
Sounds like you got more than your money's worth out of that one.

quote:

replace it now unless you like spending the night on ice in a Walmart parking lot waiting for the tow truck in a bad part of town.

If I was in a WalMart parking lot I'd just go inside, buy a new battery, install it, and be back on the road in 10 minutes! I never get so lucky...I'm usually out in the middle of nowhere when stuff dies.

quote:

Originally posted by h2oys:
Is it possible the battery just doesn't have the umph and needs to be replaced despite showing 100%?

From ~1000s of tests run, most of the time you will see ~12.5V on a 'dead' battery just off charge. A lot of the time it will start falling even with just the load of a volt meter.
A load tester will draw 10s or 100+ Amps & check the voltage under load.
Poor man's load test - if it drops below 10V when you crank it, it's a dead battery.

Back in the day cars had a voltmeter in the dash.