I have replaced the altinator and battery in my '99 Maxima. The altinator is still not charging the battery.

The only time I've had a problem with an alternator repeatedly failing is due to improper shimming and the pully wasn't aligned with with the cam and crank shaft which in turn put a tweak in the alternator pully and strain on the bearings. I must point out, this was on a 1978 Chev with V belts. The one that failed a week later, did you have it tested to be sure it failed? Same question for the most recent one. If the alternator are not indeed failing, I'l look to either the ECM or the battery cables/wiring from alternator to battery.

What model and make is your truck?
Older vehicles differ widely from later ones. Is the regulator separate from the alternator? If so, you might need to replace the regulator.
On some vehicles, the regulator was booted by the indicator lamp on the dash. If the light does not work (blown), the alternator does not charge.

check alternator voltage should be around 14 volts if under 12 then no good if altinator is good then poor battery

Altinator not charging, may be it needs from the negative post of the battery.

Check for the terminals for the battery and the alternator first. The alternator may not also be delivering current properly. Check the belt drives. Other than that it may be a bad alternator.

With the jeep running put a volt meter on the battery and it should be reading above 13 volts if not replace the altinator it isn't charging.You can check the fuse for the altinator first if not charging but most likely the altinator is bad.

Change voltage regulator. Does the battery take a charge from a charger? If not, replace battery. If it does, then regulator is faulty. If still nothing, return alternator to place of purchase, and have it checked.

if the charging circuit is low, then it appears that your alternator is going bad....

Battery terminals, when car is off, should read 12V+-.2V. When the car is running, terminals should read 13V-14V=-.2V

i would suggest you contact a dealer and tell them what happened they may tell you to bring it in and that may be a good idea when it comes to these computerized vehicles it's not always a good idea to disconnect the positive cable to check to see if the alternator is faulty it may have caused another problem doing so. The best way to check for a charge is with a machine that detects the charging system is operational

here ya go check for power to the alternator good luck ............ justuscc Charging & Starting System Wiring Circuit - VIN K