91 Ford Ranger Battery

So last week I brought my truck into the shop to get new brakes and when I went to pick it up it wouldn't start so I got a jump and drove it home and charged the battery, it started right up drove around for a while than parked it overnight. The next morning it wouldn't start so I got a new battery started right up and started the next morning. I went on vacation for 7 days came home dead battery… Could this be the alternator?

Mr. Damian, you had brakes done at a repair shop. Why not have this shop check out the problem you indicate? Guessing is not a solid foundation to repair. You do not mention problems with a battery icon showing up on the dashboard. Reading the car manual reveals that the battery icon being lit means it is the ONLY source of power for the vehicle. This happens to all cars each time the key is turned to the ON position, the one prior to START. IF the alternator is not working, the light remains ON once the engine is started. Why guess? This is a 23 year oil vehicle with about 275,000 miles. No guessing, please. Have a mechanic check the vehicle.

HI, if you had a new battery and it went dead after a few days of sitting then you have a power draw while the car is off. It could be normal as the clock/pcu and radio maybe a amp all draw constant power. Charge it and drive it and see if it loses power again. If so then maybe alternator. Have it checked for free at like autoZone.