Like fuel, batteries store chemical energy and can cause burns and poisoning in event of an accident.[41] Batteries also lose effectiveness with time.[42] The issue of charge time can be resolved by swapping discharged batteries with charged ones;[43] however, this incurs additional hardware costs and may be impractical for larger batteries. Moreover, there must be standard batteries for battery swapping to work at a gas station. Fuel cells are similar to batteries in that they convert from chemical to electrical energy, but have their own advantages and disadvantages.