Some MB batteries have been known to be bad...such as running dry in a year or so. I had a problem with a few batteries, two of them ran out in two years, back to back. But MB is good about their battery warranty. When I replaced my first one, I paid for it full price cuz it was out of warranty. Their batteries carry a 4 year warranty, so after two years when it failed, I only paid 50% of the new battery.
It's a 4 year warranty, so each year, it's a 25% pay of a new battery.
1 year fail = pay 25%
2 year fail = pay 50%
3 year fail = pay 75%
4 year fail = pay 100%
I haven't had a problem for 3 years now since the last one was replaced, so I think I finally got a good one