https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I use this battery on a garmin 4 CV, I have never had the battery die on a 1 day trip before and using for 8 hours or more in. Using a drybox with it and works perfect. Doesn't have to be $100 to work well in my opinion, and you still have money to buy a backup if you are paranoid. Good Luck.