The PowerPlus Piranha is a wind up shaver which means there is no risk of the batteries going dead. Actually, there is still a risk, but not a problem as it can be charged by hand crank.

When you want to have a good shave then wind the crank a few turns and shave away. The internal dynamo generates enough electricity to keep the thing powered for a full shave. If you cannot be bothered winding it up (when the novelty wears off) then you can opt to charge it via a plug.

PowerPlus Piranha - no battery shaver: [via]