Hi Folks,
Instead of fitting a voltage meter I decided to fit a smart warning light. The BackOFF voltage monitor functions as that by monitoring the voltage of an ignition switched circuit and displaying that by means of a single LED.
The LED reacts at the voltages below which enables the rider to tell at a glance if there is a problem or not. I used the voltage available on the round accessory plug for the optional key switch operated BMW Alarm system in the relay box which has Earth, a permanent 12 volt supply and a switched 12 volt supply via the ignition switch and load relay.

The BackOFF unit is simple to install and monitor. I chose to mount the brains inside the relay box and extended the indicator leads so as to enable me to mount the LED in the crash pad where I used the spare switch blanking plate as the mount for the LED. Took the bike for a run and noted that with the Headlight on at idle the red is on solid. Revving the engine brings up Orange and then at slightly higher revs- Green. Cyclegadgets sell them for $26.95 each. I am well pleased with the unit.
Regards,
K_BIKE

• Flashing Green (Above 15V)
  
• Steady Green (12-15V)
  
• Steady Amber (11-12V)
  
• Steady Red (10-11V)
  
• Flashing Red (Below 10V)
  

What is the size of the LED?

Bert

Hi Bert,
I just measured it and it is a 5mm LED in a 1/4" plastic mounting bezel. The other thing I forgot to say is the LED when it is showing green auto dims after a few seconds to prevent it being too bright at night.
Regards,
K-BIKE