My 94 Ranger Battery Dies by morning?

I got a 94 ranger from a buddy it was sitting for about 7 months when we started it it started right up but now every morning the battery is dead i had it checked at auto zone and they said my battery and alternator are great so i was told there was a short so i took the cables off at night and put them on in the morning and the battery wasn't drained and started right up it only does this over night it will be fine for 4 hour periods off being off so i dont know i was also told it could be the voltage regulator i have no idea if some one could help that would be great thank you