My generator cranks once a week, runs 20 minutes for exercise.  I thought it has been quiet for a few weeks, I checked the battery and it was completely dead.  I checked the voltage on the charging circuit, 0V.   The charging circuit is just part of the main board; $400 for a new board.  Not doing that just for a charger.  Since I have an electrical box 4 feet from the generator, I ran some conduit from the electrical box to the generator.  Used some Romex 12-2 with ground and installed an AC outlet inside the generator.  Then I purchased a Battery Tender Jr., very good device for maintaining batteries that just sit around forever.  Plugged it into the outlet and attached it to the battery and I was good to go.  I did have to purchase a new battery, I guess the stress killed the old one; it would not hold a charge.  You can see the green Battery Tender on the right side of the photo, just behind the propane regulator.

Products used:

• “Lawn mower” battery from Walmart
• 4 feet of electrical conduit
• 4 feet of Romex 12-2 with ground
• Waterproof AC outlet and box
• Battery Tender Jr. trickle charger
• Small amount of electrician’s putty