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Fear of frying the controller

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    Fear of frying the controller

    Hi, ebikers

    I just converted a Surly Troll with a Rohloff hub to an ebike with a Bafang BBSHD, a 52v 17.5 mAh battery, and an Eggrider v2 display. Using the configuration app that's paired with the Eggrider, and Gesslein's Hacker's Guide to Programming, I modified the stock settings to those recommended by em3ev. I played around with some of the settings based on other recommendations but ended up with em3ev's. This means that I have 9 power assist levels that begin (PAS1) with a limit current% of 52 and a speed limit% of 44. The remaining limit current levels increase incrementally by 6% and the speed limit levels increase incrementally by 7%. I have the speed limit set on the display at (shh, don't tell!) 40mph.

    My intention in converting the Trohloff (which is configured for global touring) was to provide a measure of assistance so that I could cover an average of 60-70 miles per day on a tour while loaded with 15-20 lbs of gear. I am not a spring chicken or super fit, but I am capable of covering an average of 45 miles a day, fully loaded, but I wanted to average more miles (if needed), especially in hilly or mountainous terrain. The mid-drive motor with a fairly large battery (910 A h) seemed like a good solution. So far, when I use PAS levels 1 and 2 and little throttle, the battery is capable of 125 miles.

    Obviously, speed is not my desire. Nor is scooting along with throttle assist. If I had wanted to ride a scooter, I would have bought a scooter. What I want is to generate most of the power myself, with a bit of assistance to help me cover the distance I want (or need) to cover day after day on a tour.

    The reason I'm posting on this forum is because I have read post after post, and article after article, warning of "frying" the controller. I want to be able to grind up a hill in a gear I can sustain in the lowest PAS I can use so that I am doing most of the work and feel like I'm riding a bike and accomplishing my goals for the tour. My riding style, however, is not to gear down to the point where I'm spinning at a high cadence (100+) up the hill. Rather, I find a gear that I can sustain with a cadence of around 60-70 rpm, which is lower than what most super fit, 30-year-old men recommend in their cycling blogs and articles. Apparently, the BBSHD likes to spin as fast as possible, and so I fear that my riding style will be detrimental to the motor over time (in the form of excessive heat from the strain).

    Is this something I need to worry about? Should I configure the PAS settings at different levels to compensate somehow?

    Thanks for any advice you might like to share.


    If you have a low cadence and you are going at the same speed as someone with a higher cadence, then each stroke is putting more strain on parts like the chain. Choosing a lower gear and being slower than a person at a higher cadence will put less strain on your parts.



      Higher cadence means lower motor currents which keeps things cool... 50rpm is getting too low IMO... I shoot for ~75rpmĀ± for nearly all my riding and especially if I'm battling hills or wind... for me, 60rpm is lazy pedaling although if I'm feeling lazy Click image for larger version

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      If you are looking for range, setting PAS1 current to 52% (~750W!!!) is way too high IMO - my PAS1 is 6% (~90W) by comparison and I also vastly prefer a geometric progression over linear

      My present PAS current mapping:

      Click image for larger version

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