Three-month-old battery does not charge (at all) on 1997 Volvo 850

Modern battery chargers will not charge a battery if the voltage is 10 to 10.5 volts, it determines the battery has a shorted cell. This is not always reliable, even with professional equipment.

There are work arounds. Disconnecting a battery will eliminate the small load on the battery from the vehicle’s computers, a discharged battery’s voltage may then increase to 11.5 volts allowing the battery charger to charge the battery.

Using an old type battery charger or running the engine for a few minutes can increase the battery voltage to a point which the “automatic” charger will charge the battery.

I am wondering why you are all disconnecting the battery to charge it. I have a 6 amp Craftsman battery charge rthat is 60+ years old. Never had any trouble charging a battery without disconnecting it.

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I suspect that it is to eliminate any chance of drain on the battery from the car’s electrical systems while it is being charged? This is why I was asking. But I do not really know.

There is generally no need to disconnect the battery from the car if a “smart” or “automatic” charger of recent design is used.
An old-school unregulated “trickle” charger can raise the battery voltage above 15V, which might damage modern electronics, and the battery itself if sustained for an extended time (a day or longer).

Going forward I suggest you get an inexpensive volt meter to get a better idea of what’s going on.
I use this one, for example, to monitor while the car is running:

Thanks, excellent! I will buy such a voltmeter then. How should it be read for diagnosis?

Just take the battery out of the car and take it to the place you bought it from . They will test it and replace it if it is bad . Then put it back in , start the car and go to Autozone or even the place the battery came from and have the alternator checked . Don’t make things complicated.

Thanks, yes, that is what I am going to do. The “Bad battery” indicator still is red, and the “charging” light has not come on, so this battery is not charging at all, and I doubt things will/can change at all.

A weird update. I restarted the charger from the wall socket, and now the charging light has come on (the bad battery light is also on, but I suspect that is because the battery is somehow very drained). I will see if the battery charges back fully and then look to test for parasitic drain (it is possible that there is a problem).

BTW, the trickle charger I use is the Cen-Tech Deluxe Battery Maintainer and Float Charger, item # 62813 from Harbor Freight Tools.

Here is the official product page:

This is one of the few battery chargers which will charge a completely discharged car battery (once removed from the car, obviously) assuming nothing is wrong with the battery. Most others will refuse to charge if the voltage has dropped below a certain level, even if there is nothing wrong with the battery.

I have used this to recharge the battery for my truck, after I didn’t drive it for several months, and even charged up a supposedly dead battery from a car that hadn’t run in over two years.

This charger literally paid for itself the first time I used it, and I have used it several times.

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You want to see roughly 12.5-14.5V.
The lower valve when the engine is off, accessories on (as many cars need in order to send power the the lighter/port socket).
The upper range (13.5-14.5V) with the engine running.

Is this also how I can detect parasitic drain? Most of the articles on the web suggest that I disconnect the battery (ground) and then connect it through the multimeter.

So, I have a question here: the part about “latching the door” and the trunk lid in the video. Is that because this is how we put the car to sleep while still keeping the door open/accessible? Also, I have a analog multimeter. Gardner-Bender GMT-312 Will that work, or should I first get myself a digitial one? Thanks!

Yes, he states that in the video.
Do not forget you need to have your battery fully charged before beginning the test.
Let the store where you bought the battery, charge and test the battery, then if the battery is good, reinstall then go back and have the charging system checked. If all checks out good, then do the parasitic draw test.

Thanks for the clarification, @Purebred.