TIEC UPDATES, page-192

The batteries are delivered empty, with the electrolyte added after installation. Without electrolyte, a ZBM2 weighs 90 kg. With electrolyte? 240 kg.

It's not an impossible scenario, but depending on the pallet they use, and how long it's been sitting there, it's entirely feasible that the pallet would break as soon as you tried to lift it (the static load capacity - the weight a pallet can hold when it's not being moved - is always higher than the dynamic load capacity, or the weight it can hold whilst being moved.)

Frankly, if somebody can break into the site where the batteries are stored and move out that much weight without being caught, you've got some bigger problems to worry about than just theft.