ash said:
some one told me it will over charge the battery,and can damage the charging system.....
I've heard things like that too... A proper battery re-charging system such as the one on the main engine of your Motor Home, and hopefully the one on the generator if, that is, it has one, includes a device called a REGULATOR which is specifically designed to insure the batteries do not get overcharged
I did allued to the fact the generator may not, directly, recharge the batteries (mine does not) Instead it runs the rig's normal battery charging device (the one that works when I plug into power mains) and again, if it's properly designed (NOT ALL ARE) and programmed.... It's the greatest thing for your battery since distilled water! By all means use it
My rig has a Progressive Dynamics Intella Charger with optional charge wizard... For the batteries that came with the rig, I know of none better.
However for differnt types of battereies.... I'd make different recommendations