Hey everyone. 2000 xj 4.0 auto C8.25 D30. The battery will die relatively quickly if I leave my doors open. I've tried to jump it with one of those portable jump start batteries and it will take at least a half hour of it sitting there to get the jeep battery charged enough to start. Also I'll have to rev the engine to keep it running because it will just shut off if I let it idle. I noticed that the positive cable is very corroded. Is the battery just not able to get a good charge because the cable is bad. I got the battery tested and it was fine. Any ideas? Thanks.

 

Replace Battery cable and get the battery a deep trickle charge

 

Clean up both battery cables at both ends, and check the cable itself for corrosion. Bend it in a couple directions, if you hear crunching the cable is corroding internally. A bad connection there sure will cause your symptoms.
I might be inclined to replace the cables anyway if they are that corroded, they are a regular maintenance item, IMHO. There is a member here who sells what look to be very well built replacements. 5-90, iirc?