You don't have to have 10 AA's. 8 works fine. I've gotten 20 hours out of a charge on a 3 day trip. I have the 2300 maH. rechargeables. They won't hold the charge over many days or weeks like regular batteries will. I keep reg. batteries as a back up and they seem to last pretty long too.
Heres's the info on it....
"The operating voltage of an NiMH cell is 1.2. Eight obviously gets you 10.6v when connected in series. Since most FF's are designed to run on 12 volt boat batteries will this work? Not to worry. The literature says the operating range is 10 to 15 volts. Most will probably work slightly outside of this range but 10.6 works just fine. Incidentally, I emailed Humminbird on this and they said you need 12v to operate properly and my Matrix 10 will draw 1/4 amp. When I questioned them further they said they will operate on 8 volts. Society's litigiousness makes most companies err very much on the safe side when speaking in public. We all know we don't need the full 12v and I estimate the average draw on my Matrix 10 at 165mah."
http://www.kayakfishingstuff.com/art...ak_Articles=23
http://www.kayakfishingstuff.com/art...ak_Articles=39