What is the maximum gauge of extension cord I can use to power my (TJ599E) unit? The maximum gauge of an extension cord that your TJ599E operates with are 16 gauge per 50 feet and 14 gauge per 100 feet extension cord. Related articles Does my TJ599E work on plant roots? What kind of soil does my TJ599E work best with? The battery is charged but the unit isn't turning on. Will my old Plug-in charger (ICHRG24-AC) work with my new battery? What is the maximum depth my TJ599E unit can cultivate?