Agree with above as I've eschewed them on my "e's". The only time they were of use for me was when I was testing BH's dual motor bike and (apparently, according to their engineer) the bike had a problem with the torque sensor and the motor would shut off only with the brakes. I had a really exciting ride up an 8 mile, 30000' ascent and exhausted the entire 600wh or so battery.