Smarty wrote, on Thu, 18 Dec 2014 21:53:49 -0500:

Once a year is all that it should require unless is runs a lot in
providing backup power.

In general, when there is no rain, the power is stable.

When there is rain, the power goes out once a month (on average).

Of course, it has gone out three times in December alone, so that's
just an average.

I left a message at Generac for them to tell me whether the battery
is charged by the AC mains or by the generator running weekly for
20 minutes.