You didn't mention the model , s/n or year. But most lift ruck have as standard a "lift interrupt" circuit to alert the operator the battery is 80% discharged. The forklift won't lift but they can drive the unit to the charging area. And operators have learned on on how to "override" the lift interrupt by milking teh battery down by turning key switch on and off. Then the unit dies like yours did plus this type of overriding can hurt the unit - damage controls, contactors, the battery & your "wallet" or budget (if you aren't the one paying the bills). If your unit doesn't have the lift interrupt features it can be added on some models - contact your local Cat dealer w/model, s/n.