It is best to dive into the maths here, so bear with me. The original Nissan LEAF 24kWh battery has 21.3kWh of usable capacity, of which 4kWh are your 'reserve' capacity (when the car will warn about 'low battery'). This means that in practice, you are able to use about 17kWh of your battery. The MUXSAN range extender (large model) adds 17.6kWh of usable capacity into the boot of your car, roughly doubling the range. The smaller version adds half of that - 8.8kWh, adding about 50% to your effective range.

If your car is already not at full capacity - almost a given considering eligible Nissan LEAF cars are between 2-7 years old - the gains are even greater. Here is a table of the range you can expect based on an average consumption of 15.5kWh/100km:

Even a new Nissan Leaf with 24kWh battery isn't that much of a fast charger. Compared to the 30kWh, it is 20-40% slower. However, it gets much worse as the battery ages - my 9-bar Nissan Leaf only manages 14kW maximum charging speed in winter and just under 20kW in summer - half of the original rate.

With a MUXSAN range extender, you will be able to charge at full speed (approx 42-45kW) up to 60% charge, even in winter. After which it will taper off but still be about 2X faster than your original charging speed!

The MUXSAN range extender has a lower internal resistance than the main battery, meaning when you accelerate fast or use a quick charger, it will take up most of the - relatively - damaging high currents that the original battery chemistry really wasn't designed for. In real-life testing, the main battery had 70% lower peak current going in and out at 10 deg. C outside temperatures.