Toshiba SatelliteP35 laptop keeps blacking out on “new” battery = ?

I was just back in the USA and had my laptop “fully serviced” at Microcenter (under extended warranty) plus bought a new battery through Laptops For Less in Anaheim, California. I THOUGHT all was well…however…
Now I’m back in Central America and the computer keeps “blacking out” on the battery whenever it “feels like it”…it re-starts again after awhile – on the same battery, but again blacks out whenever I keep trying to use thi new battery = ?!? HELP!
Also, the fully-adjusted-to-the-maximum sound level volume is WEAK – regardless of whether it’s through the speakers or headset = ?
Please help me/advise…THIS IS QUITE FRUSTRATING!!! ))-: