[Al Skierkiewicz]

Aj,
One and only one battery is permitted on the robot, see R34. Other battery types are allowed if and only if they are part of a COTS computing device or enclosed camera. Weight may be added provided a few items are met.
Free weights, steel plate, vises, etc. must be firmly attached to the robot. Ty-wraps, tape, wire, twine or rope, etc. do not meet the "firmly attached" definition. Attachments can be appropriate hardware, welding, etc.
As to lead, it must be entirely painted or sealed prior to attending an event. It may not be machined at the event.
As to other types of weight, notably shot, sand, liquid, etc., this must be enclosed in a container that will not spill or crack open with the forces normally encountered on the field. More than once, teams have added these items and we spent considerable time cleaning the residue from the field.
Considering the nature of the game, if you climb, it seems that additional weight would work against you.