Danbob,
This is an estimate as I've never kept close tabs...but I get about 4 hours on one battery ...that would be at the slowest trolling setting [one I think] on a Minn-Kota 32# thrust...in calm conditions.
I have two batteries...usually leave one on shore and switch when I come in at noon...they carry very nicely and are protected in the little Wal-Mart coolers you see in the picture.
I have put both on the platform at once at times and the balance remains good.
Here is a closer picture I made for Jack Hise on another thread showing the specs better...
http://img.photobucket.com/albums/v185/ ... ery004.jpg