The portable charger on its 15a setting will be faster than the 7300 because the 7300 is limited to 13.8v while the portable will go into the mid 14s voltage.
For a brief time you can get some extra amps using both the charger and the 7300 until battery voltage rises above 13.8.
Procedure is to get the portable running first without the 7300 being on, then plug in the rig. ( In case the portable gets confused) Run the gen without the 7300 on (might have to snap off its breaker if you can't stop the whole rig from getting 120v as soon as the gen comes on) Clamp on the portable and plug it in and get it going then plug in the rig or snap the 7300's breaker back on.
You can leave the 7300 on after that. It will just not be adding any charging amps except at first.
Note that the 7300's breaker may also be your rig's 120v receptacles' breaker. So when you snap it off don't worry that your receptacles don't work even though the gen is on
In future, you can get a better charger with more amps for faster charging than that 15amper.
http://www.boatandrvaccessories.com/f023.htmlThis is an excellent charger at 40amps You might be able to run your 15amper with it to get 55 amps, which is perfect for a pair of batteries (55/220 = 25% charging rate
