Car starts after jump but battery won’t hold charge

I’ve been having a lot of trouble with my 2001 Hyundai Elantra. I have had it in and out of the shop and now, it’s just sitting until I can afford to fix the next set of issues.
The current problem here is that my car will start with a jump but won’t hold a charge. I was told there’s a miscommunication between the alternator & battery. No codes can be read so, I have no idea what the issue is and at this point, I don’t even trust the mechanics around me. We thought it was an issue with the alternator so, I replaced that but something is still draining it and everyone tells me they can’t do anything without actually looking at it. Is there anything I can check or do to save some money? Because at this point, I can’t afford to have it towed and have it in the shop again.

You could put in a new battery and then diagnose the current drain with a VOM. Without a functional battery, you can’t really figure it out.

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We’ve tried putting in another battery and it did the same thing to that one so, we know it’s not the battery.
Also, thanks for replying back so quickly!

OK so something is draining the battery. This is not necessarily an easy thing to pin point but it starts with hooking up a test light or meter and pulling fuses to see if that changes the drain. If you are lucky enough to find a fuse that kills the drain, then you can look at what is malfunctioning in that circuit.

Prime suspects are glove box or trunk lights that don’t shut off but I have had the door handle switch that turns the interior lights on and the electronic level control module. In both cases just found it by accident since it was intermittent. So really, yeah someone that knows something really needs to start doing the diagnosis.

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Try this!

Just out of curiosity any aftermarket stuff? radio, remote start etc.

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No, I don’t believe so. Thanks for the article, I’ll check it out!

An alternator can’t be relied on to recharge a severely discharged battery. What does work is a battery charger, preferably one that can be set to charge slowly overnight and then cut back to a trickle charge. If your battery has removeable caps, you can measure the state of charge (specific gravity) in each cell before and after a charge. The tool, like a baster, sucks some battery acid into a transparent compartment. Inside a float with a scale, or floating balls, tell you the SG. That tells you if each cell can take a charge. If you measure later and the SG has gone down, that is a cell that is not holding a charge.

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What I’m trying to convey is that without a charged battery in the car, you can’t diagnose this.

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The battery is charging right now but what I’m saying is, we have charged the battery and jumped it and the charge will only last for about a minute or so and cut off. The battery won’t hold the charge. And I was told it is because of a miscommunication between the battery & alternator. But I’m trying to understand what could be causing that miscommunication.

Not sure. Some batteries cannot hold a charge. If you remove the battery to charge it, you are decomplicating the situation. See if it takes and holds a charge, without any connection to the car. (You may have to reset radio memory, etc. Check owners manual about that. In some cars it is a big hassle to remove and install a battery unless you have special equipment, so I don’t want to suggest some step that might add to the mysteries.)

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You are aware that your alternator can fail and become a big giant hole into which electrons will flow… Yes?

Do this quick test… unhook the hot lead from the alternator and then hook up your charged battery. Be sure the hot lead cannot or will not ground itself as it is a direct connection to the positive terminal…but easy to do just for a quick test. If the car runs and functions normally and the battery does not go dead you just found the problem. A digital volt meter is extremely helpful if not mandatory for most of the tests I could also tell you to perform…but lets start with the easiest and quickest test… Unhook the alternator lead.

In instances where the alternator is the culprit the alternator will be warm to hot to the touch on a cold engine and with a charged battery…big clue there.

The alternator is brand new. I thought that was the issue so, I already had it replaced. We checked it with a volt meter too and it was at a 16.

If the battery won’t hold a charge, it is shot, period. That doesn’t mean there aren’t other electrical problems, though.

We have tested another battery and it did the same thing

Tested it on its own or installed in the car?

A good battery will not not discharge in a minute or so. How are you testing the battery?

Installed in the car

Check the voltage at the battery terminals with the engine running after being started with a jump. If it’s at least 14 volts, there is no “miscommunication”.

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That’s apparently the case even now.

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The battery has been checked several times. It had like no voltage. No power and this was after being charged and after being jumped. So that is why I was told it’s a miscommunication between the alternator & battery. I even charged it for hours today and it was completely drained as soon as I tried starting it.