Plug your 30AMP Shore power cable into the generator 120VAC connector using a RV30A-15A long Adapter (WALMART) to use your on-board smart mode converter/charger to charge your batteries.
Or purchase a smart mode 120VAC Battery charger and plug that into your generator. Then connect the battery charger cables to the battery terminals...
The point that everyone wants to pass along is you cannot use the "BAT CHARGE" pins on the front panel of the Honda Generator to charge your batteries... It will take TOO MANY hours to get your battery back up to its 90% charge state doing this...
You want to start each camping off the batteries session with them charged up to at least their 90% charge state otherwise the batteries will quickly discharge on you. Continuing to do this will do internal harm to your high dollar battery.
Trickle charging your batteries for 30 minutes or so and then running them down below their 50% charge state will quickly do harm to your batteries... Always start out with at least a 90% charge state. Getting your battery to its 90% charge state using smart mode charging will take around three time.
This is what we do at any rate and my 255AH battery bank was installed back in late 2008.
Roy Ken