Like I said, for the HG2 not more than 60 watts each. Over stretching a battery is highly unwise. At best you will reduce their lifespan, at worst it's fireworks time.
If you
really wanted to run 200 watts on two
batteries, then you could use the LG HB2/4/6 which have a 30 amp CDR, as long as you did not let them get below 3.7 volts.
Use steam-engine to
model this. Remember that coil resistance is irrelevant, what is important is wattage. Set to regulated, power regulation on the left, look at the battery drain box on the left, divide by the number of cells accordingly.
You will find
this useful too