I have a question but I feel a little stupid asking it. My Cherokee Sport battery has been draining to a point where my Jeep wont start after 4-5 days. I can jump start it and after a while of running, it starts again easily. But the battery still dies after sitting for a few days.

The battery is 4 years old so I thought maybe it was going bad already. I took it to Advance Auto Parts to have them check it and also the alternator.

The guys there tested the battery and said it was good but needed charged. He said that he could not test the alternator until the battery was charged up. I told the guy that I would let it idle for a while so the alternator would charge up the battery. He looked at me like I was stupid and said that the alternator would not charge the battery and I had to use a battery charger.

Am I missing something here? Why wouldn't the alternator be sufficient to charge the battery?

 

here's a simplified answer to your question



"Yes, there is a wrong way to charge your battery. The absolute worst thing you can do, is jump start the car, then drive it, to let the alternator charge it back up. This almost always ends up in a double disaster. Not only is the battery poorly charged, but you’re lucky if the alternator still works. You must have a battery charger to charge a battery without causing some sort of damage elsewhere."
"However, the higher amps rate you charge your battery at, the less efficient the job gets done. Sure, it gets done faster… but not properly. The best way to charge a battery is to trickle charge. This takes all day, but it does a way better job.
When you charge a battery, think of washing your car. First you put the soap in the bucket. Then, you turn on the hose full blast, to try and fill up the bucket. When the suds clear away, you’ve only got a quarter bucket of water. Now you have to start all over again. It’ll probably take you about three times to get a full bucket of water. All you had to do, is turn the water on slowly and be patient.
Same thing with your battery. If you shoot a lot of amps into it right off the bat, all you get is a surface charge that will soon dissipate. But if you trickle charge, the amps sink deep into the cells completely restoring the amp hours to the manufacturers original specification"


taken from


http://www.alternatorrebuildkits.com...rge-a-battery/



The alternator is meant to keep the battery topped up, replenishing the charge used by the electronics of your jeep, it is not meant to be a charging device. You can get small trickle chargers for cheap nowadays. I got a Motomaster one from Canadian tire with a jump start or trickle charge option and automatic shut off so you can leave it on overnight without worrying for $30 on sale. I've seen cheaper.

 

Thanks for the info. lol I guess I was taught by the wrong person. Thanks for the info! Much appreciated..

 

It's a common misconception. I used to do the, "jump start and let it run for awhile and you will be good" thing till I learned better.

Welcome to the forum BTW!

 

no problem. I learn new things on here every day so it feels good to help someone else out.

 

Great answer, nice input. Does make a lot of sense, considering the electrochemical work being done.

Indeed, a 4 year old battery has done its time, so unless it runs daily, it would not last that long.

But the deal about jumpstarting a dead battery, that is what probably killed mine. I let mine a whole year without working (a big no no) so I killed a new battery. Oddly, it worked fine for a whole week, but it must have drained (another issue that kills a battery) and did not survived the bad recharge.

Its a *****, that sometimes the alternator voltage regulator does not start to allow charging unless we push the throttle, draining the battery...