I also use the B&D VEC1093DBD 40AMP smart mode battery charger. This will re-charge 12VDC deep cycle batteries in a quick three your run time. I connect this portable charger to my 2KW generator when needed.
The VEC1093DBD smart mode charger draws 785WATTS on the AC side and works well with my 2KW Honda Generator. Not sure what the MAX OUTPUT is from the Honda 1KW Generator. It is probably around 900WATTs...
The RULE OF THUMB is if you want to re-charge a DEEP CYCLE BATTERY to its 90% charge state in a three hour time frame you need to hit it with 14.4VDC with 18-20AMPS of DC Current available. Two batteries will take 14.4VDC with 36-40 AMPS of DC Current available if you want to charge them in a three hour time frame.
The unregulated 12.0VDC at 8AMPS from the Honda BAT CHARGE ports will take probably way over 24 hours to just get your battery to its 90% charge state. My generator will only run 6-7 hours on one tank of gas hehe...
