I charged up an old (but never used) battery overnight. idiot light charger says it's charged. I put the multimeter on it and got

VDC: 11.43

I clicked it over to what I thought was DC Amps and got 3.5


I tried the tester on a known good battery and got VDC: 12.41 and DC Amps (or whatever that is...saw A figured Amps) of 4.3

Can I tell from these readings if that first battery is going to be OK to use?

thanks!

Let’s address the most serious issue first! AMPS! You CANNOT test amps by touching the probes to the terminals like you do volts!!! Amps must be tested ‘in circuit’ with a load, and a typical VOM meter cannot handle the current flow (amps) of a good battery under load! You need a load tester, even a cheap Harbor Freight unit can suffice. A meter will blow its fuse, you hope, or it will be fried.

A reading of 11.4 volts is a very dead battery. I suspect your charger never kicked into charge because it never sensed a load. This is where a parallel hookup with a good battery can help. Try that. Connect the batts positive to positive and neg to neg then attach your charger. As the charger charges both batts at some point (maybe after an hour or so) you should be able to remove the good battery and charge just the dead one, by now you should get a better volt reading on it....like maybe 12 volts.

If the batt is any good it should charge to 12.6 to 12.8 ish. How much capacity it has is still in question and can only be tested under a load.

After charging, should also do a load test on the battery, just to make sure it's holding a load.

I've always put a hydrometer tester in each of the cells to get an idea of what I have.

Years ago I had a Sears battery in an old car and it would test across the posts as charged at the place where I bought it, but it still turned the engine over very slow. The hydrometer test I did later showed some of the cells were too low.

The little charger is probably seeing a surface charge and stopping. Smarter ones will look for this and also acceptance rate of charge and flag when a battery isn’t taking.
As stated put a load on and test with a meter. Otherwise you are looking at open circuit voltage which is not a good indicator.

A friend sent me this:

On a side note something I saw on youtube (fwiw!) they said new batteries on the store shelf, you want to grab one that has the newest mfr date, that they slowly go bad just from sitting too long

i have been doing that for many, many years now. sometimes, the fine print on the warrentee states that it starts on the date of manufacture, NOT the date of sale ! my brother found that out the hard way years ago. it took LOTS of complaining to the parts store that sold it to even get a pro-rated refund !
ALWAYS get the newest date possible, and ASK the clerk to make SURE you understand the warrentee !

What's the feeling about desulfating chargers and their ability to restore old batteries??

https://www.thedrive.com/reviews/31119/best-battery-desulfator

I think the challenge now is with "sealed" batteries and trying to desulfate and risking burning off electrolyte, so they probably dont push the battery too much. People are not used to even looking at this now or in some cases, cant even get the caps off.
When I was a kid my Dad would use a pretty healthy manual charger and charge them hard, but maintaining electrolyte level, so the plates stay covered. And you can test the specific gravity to see if it is working.
I did this with my old restoration battery to keep alive about 11 years. Worked for a long time, but in the end the battery self destructed one day during cranking and exploded. That was a bad day.

My local Advance store considers batteries that have sat on the shelf for 18 months "used" and sells them for $42.99, I have bought many of these and most work fine.

I've also always looked for the newest date sticker when buying batteries.
Has anyone done the epsom salt trick to get some more life out of a bad battery? A buddy of mine has done that to a couple of my batteries now to get some more life out of them.

I saw another utube vid (how I have been spending my isolation!) where they charged a bad battery with 4 loads of distilled water (iirc) & it restored it, shouldn't be too hard to find. & noted that the mfr day issue is legitemate

If the battery is 4 years old or more..get rid of it

Our Optima blue top is going on it’s 11th boating season. In the winter it’s duty is to power the winch in our race trailer. I have no idea why it’s still alive. The Arizona heat is pretty good about killing batteries