Electrical Help!

[TheJay]

Ok, I have this 1991 K5 Blazer, and i cant figure out this problem for the life of me. It has to with my battery not staying charged. When I drive it, the voltmeter that is in the dash will go up past 13 volts like its suppose to, but only when im accelerating from a dead stop(like when i pull out onto a road), but whenever im coasting, idling, backing up or anything else, my alternator wont charge my battery. I have replaced the alternator, the battery, Ive check all the connections i could think of and i even replaced the wire that goes from the alternator to the battery.I had my alternator tested at an AutoZone. I cant drive for more than a few days without getting a dead battery. this sucks because until i can fix this problem i have to hook my battery up to a charger twice a week. I cant keep doing that. If anybody has any ideas or solutions, please fill me in!