Charging a car battery w/o a charger

I have to sell my car. Not fun, but necessary. When the battery died, I replaced it, and three days later it went kaput. I got the alternator replaced, but it blew out. So did the second and third. The fourth never got hooked up, and wiring problems were discovered.
So I got the battery charged, and drove the car to where I’m selling from. A charge lasts about 3 days, since the alternator isn’t hooked up.
I’ve had an offer (yes, I told the prospective buyer what’s wrong with it and how much the parts should cost), and realised that the battery may have drained.

So my question is: How can I recharge a battery that won’t hold a charge…without a battery charger? Is it possible to jump-start it, and let the car I’m jumping from run for 20 minutes or so? Or does battery charging not work that way?

You can connect it to another, running car, just like jump starting it.

But don’t start it, just leave them connected for a while. This will let the alternator on the running car recharge the battery on your car.

No need to start your car until you are going to drive it off.

Beauty! That’s what I suspected, but I didn’t want to try it without having heard from someone with more experience than me.

Your main problem should be found, or your charge won’t last at all.
In my case I found that the wire from the battery to the starter was flapping loose and had gotten a bare spot where it rubbed the wheel well. The battery would charge, but if the car stopped with the wire resting on the wheel well then no juice would reach the starter. A new wire and the long-running problem was gone.

Just disconnect one of the battery leads while the car is sitting there and reconnect it when you want to start it. A fully charged batt. should last a hell of a lot longer than three days. It’s obvious that you’ve got something drawing power when it shouldn’t be. That’s why your batt. in dead in three days.

What he said

I add in disconnect the battery positive side in the old car, before you go charging it. After setting for a few days without a positive connection and it’s still dead the battery is bad from your wiring problems.

You can also swap the batteries from the non recharging car (car A), with a working car.(car B) You can then jump start car B with car A, and drive car B around until the battery is charged. Then later, swap back.
This also works to get a car home that is stranded with a dead battery and alternator.

I’m having trouble separating the confusing part of this from the wrong part.

Electrically, it doesn’t matter which battery cable is disconnected. There cannot be a complete circuit unless they’re both attached to the their respective battery terminals.

Practically, one should not disconnect only the positive cable. There’s a risk of accidentally shorting between the positive terminal and ground, which causes undesired arc welding. Always disconnect the negative first (and reconnect it last) and it will not be possible to inadvertently create a short circuit.

If a battery loses its charge sitting disconnected for three days, the battery is faulty. If it loses its charge in three days only when connected, there’s an excessive electrical drain in the system.

I said disconnect the positive, to isolate the battery. You can disconnect both terminals if you wish, or the negative.