390x battery differences?

[kittstr]

The battery that came with my thinkpad is a 10.8v 4800ma Li-Ion battery. It wouldn't hold a charge. I bought an aftermarket "high capacity" battery. When it arrived it was a 9.6v 4000ma NiMH battery. How can these both be vaild for the same laptop? Don't they at least have to be the same voltage? Did I get ripped off?

Thanks for any help you can provide.

Andrew Strouse
( kittstr@earthlink.net )