I'm having triouble keeping my battery charged

[fsj1979]

Sounds to me you're overcharging and cooking the battery. It just took two weeks to kill the new battery. It'll take a charge but now won't hold it after you ruined it by overcharging.

Overcharging?......with 13 volts? NOT likely. Every vehicle I own puts out between 13.8-14.3 volts. A good battery will hold a steady 12.5 with no charge at all. A flat 13 volts is really a very poor charge. I suspect the voltage regulator in the alt. is bad. At certain rpm's you may not be getting a charge at all.

[Carnuck]

13vdc isn't enough to fully charge the battery. First thing I would do is see if it's the wiring between the alt and battery causing the problem (very often the ammeter is the culprit) by putting a jumper lead from the alt main terminal to the battery + and recheck voltage.
How old are the belts? They can be tight but worn too skinny to grab the sides of the grooves (which is why serpentine belt system is superior). They can actually drop down the groove till the bottom of the belt slides on the pulley.
Is there a ground wire from the battery negative to the body? Without that, the headlights will draw away power from the alt's field plus the lights, heater fan, and wipers and it's even worse. Everything works slower, harder and heats up till they fail.

[mdcptman]

I agree, 13v is too low. Should be 14.5

[The Colonel]

I agree, 13v is too low. Should be 14.5

14.5V???? Good luck finding that on one of these rigs....in stock form anyway.

[Carnuck]

Mine ran between 13.9 and 14.5 after I bypassed the ammeter and added a fresh battery to body ground.