The Charging Converter can charge two batteries at the same time. Connect the DC charging port to the converter, then connect the two DC ports to the two batteries.
Note: it will charge two batteries at the same time only when the voltage of the two batteries is less than 2V: If the difference of the voltage between two batteries is more than 2V, the charger will charge the low-voltage battery first.
Please take the battery off the bike to charge while using the dual battery charger, to avoid the battery entering into “sleep mode”