The sales pitch for lithium-ion forklifts always highlights "opportunity fast-charging." Unlike lead-acid batteries that take 8 hours to charge and 8 hours to cool, a Li-ion battery can be plugged in during the operator's 15-minute break and absorb enough energy to run for another 4 hours. It eliminates the need for a battery room and spare packs. But the sales pitch ignores the physics of the building's electrical grid.
A single heavy-capacity Li-ion forklift on a fast charger can pull 80 to 120 amps at 480 volts. If a warehouse plugs in five of these trucks simultaneously during a lunch break, they are instantly dropping a 500-amp load onto the facility's electrical service.
Older distribution centers built in the 1990s simply do not have the amperage capacity at their main switchgear to support this. When the trucks plug in, the main breakers trip, shutting down the warehouse lights, conveyors, and IT systems. To safely deploy a fast-charged Li-ion fleet, facilities are being forced to spend hundreds of thousands of dollars upgrading their utility transformers, pulling new 4/0 AWG cabling to the dock, and installing dedicated power distribution panels. Furthermore, utility companies are hitting these warehouses with massive "demand charges" on their electricity bills for those 15-minute spikes in power consumption. The forklifts might be cheaper to maintain, but the cost of feeding them electrons at that speed is staggering.
