If the batteries are lead acid (gel cell or AGM), then you are allowed to run up to 73 lbs regardless of their rated capacity or voltage. Check that your controller will work with the voltage.
If the batteries are any of the advanced types then there is both a weight limit and the battery capacity in Watt-hours must be 1,000 Watt-hours or less.
The weight limit for lithium ion is 15 lbs. The others are listed in the manual which can be downloaded from the ElectrathonAmerica website.