so after i give my buddy xj a jump, later on that night i start losing power, and the battery drains. i meet up with him the next day and come to a conclusion that its the alternator. so i go buy a new one and install it, still nothing. says i need to jump it, my question is, after i jump it, when i turn it off again, will it start up without a jump? will jumping my xj cause the new alt to charge up battery? could my battery just be bad amd i bought an alt for no reason? my ac blew with the old alt but i still bought a new one, dont know if that even matters but yea...

 

How old is the battery? If it's older than three years old you may want to replace it.

 

You need to start doing some testing to figure out the true "root cause" of your problem.

Testing the charging system is not that difficult With a basic meter hooked up to the battery, a good system should read between 13.5 and 14.2 volts at high idle. If you don't have a meter, get one. Basic ones can be purchased for $10 or so. You can get a nice one for $25. Parts stores will oftentimes test your charging system as well for free, but get a meter and you can do it yourself.....

The battery itself can and should be "load tested" which can be done at any parts store for no charge. Absolutely get this done! Load testing is the only conclusive way of testing a battery. Voltage testing can absolutely be inconclusive. And while you're at it, be sure battery connections are solid and squeaky clean.

Jumping a battery only provides enough short term juice to start the engine. If the battery is truly low, it should be properly charged using a battery charger. The alternator on your engine is meant to "keep" a battery charged. It is not meant to charge a depleted battery.

EVERYBODY that works on their own vehicles should have a battery charger. And you should also have a multi-meter. And posess the basic ability to use both of these.......Good luck!

 

i have a multimeter but will deff be getting a battery charger soon. thankyou. i hope i have a good battery

 

but just because my battery has no power now doesnt mean its a bad battery right?

 

How is your negative lead? Will the starter crank? If it won't crank try popping the solenoid with a pipe. If you have a Hi-Lift the jack handle works really well. I've had similar issues in the past and once it was a the ground and the other was the starter. I really would have been much better off if I had had a multimeter but hey, you live and learn.