Yes. Individual orders within a batch can have different weights, as well as different contents.
As long as ALL the orders in the batch will be sent via the same service (ex: USPS First Class Mail) and package type, then you can get simultaneous rate quotes for all orders, even if they have varying weights.
For example, if you have 10 packages that weight 3 oz, 6 packages that weight 5 oz and another 14 that weigh 9 oz - they all qualify for USPS First Class Mail. You can batch all 30 together, assign USPS First Class Mail to the batch and we will return a rate quote in seconds. 1 click, many labels.
How to: Create a batch shipment
How to: Batch orders by weight
How to: Override weights for all shipments in a batch
How to: Edit a shipment within a Batch
Best of Rules: Assign carrier selection to a batch of orders per requested service