Warehouses are desperate to keep trucks running 24/7. The industry pushed "opportunity charging"-plugging a lead-acid forklift into a fast charger during operator breaks and shift changes instead of doing a full 8-hour equalize charge. It keeps the trucks on the floor, but it is destroying the batteries at an alarming rate.
Lead-acid batteries are chemical reactors that need time to absorb the lead sulfate back into the electrolyte. When you hit a 75% discharged battery with a high-amperage fast charge, the lead sulfate cannot convert fast enough. Instead, the excess energy goes into electrolysis-splitting the water in the acid into highly explosive hydrogen gas and oxygen. The battery overheats, boiling the electrolyte.
Operators, seeing a battery that reads "80% charged" on the screen after a 30-minute fast charge, think they are good to go. But the voltage is artificially high (surface charge), and the specific gravity of the acid is still weak. The truck goes back to work, immediately drawing heavy current, and the voltage collapses. Over months of this abuse, the positive plates warp, the active material sheds to the bottom of the case as brown sludge, and the battery suffers a sudden, catastrophic thermal runaway, melting its posts and filling the warehouse with sulfuric acid smoke. Opportunity charging works perfectly for lithium-ion; for lead-acid, it is a death sentence.
