#cycleanalyst

Before I talk about my experience putting everything together on the bike, I wanted to write a quick post about another “extra credit” component I added to my electrical system -- a Cycle Analyst:

The Cycle Analyst was recommended to me by a few different people and it’s definitely an awesome tool. It serves as a digital dash for your bike that provides tons of useful data. The Cycle Analyst displays real-time system voltage, current, power output, and cumulative Amp-hour (or Watt-hour) energy usage. This is super helpful for diagnosing any weird issues you might be seeing and for getting a feel for how much energy your system is actually using at any given point. It also has a sensor for your wheel to act as a speedometer and odometer as well -- all around a super useful addition to the system. There are some other features that the Cycle Analyst provides that I’m not taking advantage of or mentioning -- check out their site for more details.

There are a couple different variants of the Cycle Analyst; I got the High Current (HC) version of the Cycle Analyst V2.3 (the most recent available when I got mine). I bought one from Electric Motorsport, but it looks like you can get one direct from the manufacturer (with shunt, which I’ll explain shortly) for a bit cheaper. The regular Cycle Analysts are for lower-powered electric bicycles -- the HC is more appropriate for my system. 

Before going into how the Cycle Analyst is wired to the system, I wanted to talk about the shunt (pictured above) and its role in measuring system current. The shunt serves as a very accurate and low-resistance resistor that is wired directly in series with the circuit whose current you want to measure. It has two large terminals for connecting it in series with the high-power circuit, and two smaller terminals on either side of the shunt to connect to the Cycle Analyst to measure the voltage drop which allows current to be calculated. Having this external shunt allows for the flexibility of selecting a shunt designed to meet your system’s current needs, opposed to having the system’s current flow directly through your measurement tool like a typical ammeter. The drawback here is the need for calibration -- the shunt has a known resistance, which needs to be entered into the Cycle Analyst for its current calculation (I=V/R).

The wiring of the Cycle analyst is pretty straightforward. It comes down to just 4 wires -- power (V+), ground (V-), and two wires that connect to either side of the shunt to measure the voltage drop across it. The shunt is wired in series with the high-power circuit in between the negative terminal of the battery and the negative terminal input on the motor controller. As such, the ground wire and one of the shunt measurement wires are crimped together, so you only need to hook up the V+ to your positive battery voltage and the two measurement wires (one of which is combined with ground) to the two terminals on the shunt. Details on which wire is which are detailed in the manual. With these voltage and current readings, the Cycle Analyst can then calculate power (P=IV) and accumulate charge (Amp-hour) and power (Watt-hour) usage.

The last part of the Cycle Analyst I’m taking advantage of is the speedometer sensor. This is a magnetic sensor that you mount to the fork on your bike, and mount an included magnet to the wheel. When aligned correctly, the Cycle Analyst is able to measure rotations of your wheel. You must enter into the Cycle Analyst the circumference of your tire such that it knows the distance traveled per wheel rotation. While having a speedometer is obviously useful, this also allows for the Cycle Analyst to measure your energy usage per mileWatt-hours per mile (Wh/mi), akin to miles per gallon.