What is the Unagi’s range on a single charge? How can I preserve battery life to maximize range?

Most riders can expect a 7-12 mile range on a single charge.

Please note that range is subject to a number of widely varying factors. In general, the faster you go, the more power you consume. Braking also consumes power to engage the electronic brake. Hills are a major influence as they consume extra power not only going up to overcome gravity but also going down to keep you at a safe speed. Acceleration is another important influence. A continuous ride at a constant velocity will consume less power than an equidistant ride with frequent stops. Gradual braking and accelerating will consume less power than heavy braking and accelerating. Slow down early by easing off the throttle, rather than hitting the brakes late, and accelerate gently rather than jamming on the power all the way. The driving modes 1-3 have caps for top speed and acceleration, so lower modes will give you better range. Dual motor mode will consume more power than single motor mode. Temperatures below 50F or 10C will negatively impact battery capacity and reduce the range by as much as 30%. Other factors that contribute to the range include rider weight, wind, and road surface.

The theoretical maximum range according to the specifications of the battery and motors is 15.5 miles. This applies only to optimum riding conditions, meaning a 150 lb. rider going at a steady speed on a smooth and flat surface in warm weather with no wind resistance.

If your battery dies mid-ride, you can walk it next to you or drag it while balanced on the back wheel. Alternatively, it is possible to use it as a kick scooter while powered off, but it would be quite a workout. The wheels have built-in magnets as part of the high-power motor mechanism that causes extra resistance when pushing the scooter manually. Plus, the electronic brakes do not work without power, so you must rely on the rear friction brake which is much less responsive. Going down a steep hill while the scooter is powered off could be very dangerous."

See here for tips about maximizing the lifespan of your battery.