A bit more expensive than that ($20) but typically the meter in that APT display is not to bad. There is a setting, without the programming cable, to select battery voltage for the battery being used. That said I can't imagine a voltage reading being a game changer. Typically Bafang users are quite happy when repairs can be done by the user and not locked into a shop. BUT if the user wants a bike with excellent torque sensing, Bosch is the hands down winner. But the offerings from Bafang will run circles around Bosch for speed and raw power.You should ask him to get the$10 USB cable and tune his motor. Simple changes in the parameters will make a huge difference.