I also say no and agree that on battery would be charged first which also means that the during the initial phase of the charge cycle where a high rate of charge (amps) is delivered to the battery cells to clean off the plates. Too high of an initial "blast" will shorten the battery life and great excess gassing cause the electrolyte to "boil" out. A chargers max amp out put should be not greater than = or - 5% of the batteries AH rating.
Equalize charge might solve this but the down side the total charge cycle time is almost doubled - that's why some people call it the "week end" charge. But the cost of "experimentation" can be expensive.
Suggest you call a battery/charger dealer and trade in your charger for two right sized chargers - chargers in good condition can bring in a good trade in price. Shop it around with a reputable company.

generally i'd say no but...

what type of battery's are these? and what are they in?

if the batteries were hooked together in parallel it might be possible though.
the only problem with this though is they will not charge equally as the first battery will get the better part of the charge
maybe if you did it using the equalizing charge it might work better this way