Should I fit an amp meter or volt meter? - 4QD - Electric Motor Control

Should I fit an amp meter or volt meter?

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Fitting an ammeter is a much debated subject, from our perspective we see the following;


  • Can be interesting to see what you are using.
  • Can indicate mechanical faults.


  • Needs a shunt [adds losses], or Hall effect sensor [expensive].
  • What exactly is it measuring? [battery and motor current are usually different].
  • Most meters are not calibrated for measuring square wave PWM currents.


A battery voltmeter is more useful Рwe would even say essential  since, as the battery discharges, its voltage drops, so this will tell you the charge state of the battery. Also, under heavy load, the battery voltage dips. If the voltage dips too far then either the load has increased or the battery is getting old.

4QD have LED meters available (3 LED for 12v systems, 5 LED for 24v and 36v, 7 LED for 36v and 48v systems) which can be useful. They will show the voltage dips as you accelerate and will indicate the charge state. LED meters, working in steps, can never give as precise an indication as a more expensive digital voltmeter, but they can be very useful and better than most of the cheaper battery state indicators. They also give a nice display!





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