We bought a house and have both a battery operated mower and trimmer. The lawn mower I can do 3 or 4 times cutting the back and the front before charge. The trimmer I can do twice, but I have two batteries so I can just swap on the fly if it dies.

However…if you let your grass grow 'out of control' and try to cut it, it sucks the battery life. I found that out when returned from vacation.

http://shopping.yahoo.com/p:Black%20&%20Decker%20CMM1000%20Lawn%20Mower:2000641658

They have great reviews, and can do up to 1/3 acre lots.
Good Luck,