The 4NE4C firmware is a version of the 4NN4C update that was created by Nissan correcting the miscalculation of range for 30kWh LEAFs. This 4NE4C version has is altered to help reduce heat in the battery pack when the vehicle is fast charged.
On the first 2 DC charging sessions this firmware is unnoticeable, after this it will start ramping down the DC charging rate, the speed will vary depending on the heat in the battery pack.
Vehicles applicable 30kWh LEAFs are registered between 2015-2016 and the odd 2017 model. Registration dates don't always reflect build date so best to enquire first as we can see if this update is required.
Bookings are essential for this update.