Can’t Keep Battery Charged. What’s Going On?

Newbie finally got my 73 back from the mechanic after 1 year! Long story.......Jeep has rebuilt engine including New Battery. I drove it home no issues even though it hesitated a little to start. Next morning would not start. Charged the battery. Started up. A week later (today) would not start again. It did sit for long time. Thoughts? Frustrated in Gainesville Fla! Thx.


Carlos

 

1) Is the battery charging when the engine is running? Touch the multimeter's probes to the battery terminals when the engine is running. Are you getting at least 14v?

2) Is there a vampire drain on the battery when the ignition is off? For that, you've got to put your multimeter into amperage mode (probably having to move the red wire/probe into the amps socket on the multimeter), removing the negative lead off the jeep's battery, and connecting the probes in series between the battery negative's terminal and the disconnected ground lead. Then hope your vampire drain is less than 10 amps to prevent blowing the fuse in the multimeter. Best to use one of those free Harbor Freight multimeters. If the meter shows any value other than zero, you've got some sort of drain. Start pulling fuses one at a time while monitoring the current drain. I had one of these vampire drains on a jeep and the PO had wired the tachometer in before the ignition circuit, so the tach was minutely draining the battery 24/7.

 

Thanks. I’ll check it out. Appreciate the knowledge.

Carlos

 

Ditto on the shared knowledge. Let us know what you find out, Carlos.

To my knowledge, those days of free multimeters and tape measures from Harbor Freight are long gone, as is the weekly 20% off coupon. Cashier said they stopped all that in February.
I have a box of those meters I was trying to give away. I guess I will keep them for sacrificial use...

 

Since it sounds like you paid a mechanic to get the Jeep running, i would think they should diagnose the problem for free. and probably fix it for free as well depending on the situation.

I had a similar sounding issue with my Jeep. There was no parasitic drain; the battery wasn’t getting a charge. Couldn’t figure out if it was the regulator, alternator or exciter wire. I ended up buying a one wire alternator and it fixed the problem immediately.

 

Either a parasitic drain, or a dud battery. A good battery will hold a charge for many months.

You could charge up the battery and see if it holds it's charge when disconnected. And/or try substituting a 'known-good' battery in the vehicle for a while.

 

If it still has an external voltage regulator I would start there.

 

All of the above posts were great suggestions. I was just going to add that it's not at all uncommon to have small parasitic drains on our rigs, even with modern upgraded wiring. Some of us choose to keep a few accessories unkeyed or "hot" all the time, such as CB, off-road lights, rock lights, winch etc. That said, these drains should be small. You definitely want to make sure there is no large drain somewhere. I've noticed my battery begins to get a little weak after a couple weeks of sitting if I don't turn off the master cut-off switch. In my opinion, nearly all rigs should have this switch. These switches are quite common and, in addition to saving the battery, are also a really good idea for safety and even security. Good luck.

 

Thanks all for the feedback. Keep you posted

 

In your opinion, should that switch be one of the simple battery post switches or one that is wired in under the dash somewhere? Or is there a difference?

 

I like having the switch inside the cab of the rig, so that I can quickly access it if there should ever be an electrical emergency of some sort. Luckily, I've not had to access it for any type of emergency. I got my switch from Summit. It's the kind with the red handle that can be removed once it's turned off. It's super easy to install, though you'll likely need to get a couple of longer battery cables. Cole Hersee is also a good brand, and they make a lockable battery selector switch. However, that particular switch is more bulky. Also, not all switches have the same amperage ratings. I try to make sure to get the most heavy duty one possible.

 

It seems like I also need to put a cut off switch on mine as well, if I let it sit it will drain the battery, mine is either the wiper motor, horn or the heater fan, all seem to be wired with constant power.

Wiring is not my favorite thing to look at, eventually I will get to it.

 

Fwiw the switch goes in the ground wire.

 

JMO - you should measure the drain with the amps setting on your multimeter. This will enable you to isolate the source of the drain. A cutoff switch is a bandaid for a problem you should not have, IMO. Up to you - JMO.

I also feel that any car that sits idle a lot should be on a battery minder. For me, this makes a huge difference in how long my conventional lead-acid batteries last. I also suggest an electronic battery checker to track the condition of your car batteries.

 

x2

 

When your "mechanic" put the electrical system together, did he polarize the Generator/Voltage Regulator?

 

Update: I put on a trickler and have been running it. (200 miles since rebuild). So far no issues.Took the trickler off for one day and started up OK,.Might have dodged a bullet!