Couple of questions.......

Discussion in 'Electric Bikes' started by BilboSmeggins, 16 Sep 2018.

  1. BilboSmeggins

    BilboSmeggins Über Member

    Firstly, is an electric assist legal if it exceeds 250watts, but is restricted to 250watts via software. I’ve seen a bike I’m interested in that falls into this bracket.

    Secondly, I already have a recumbent trike with the Steps Shimano system on board. If I’m tackling a large hill with assist, what is the most economical way of doing it? Either zoom up the hill on max setting, but it all be over pretty quick, or dawdle up the hill on min assist, but have a much more prolonged draw on the battery?

    Unfortunately, my system doesn’t give an exact battery percentage remaining figure, only five bars, so it’s possible to be up to 19% out on the guesstimate at any one time. So I can’t cover the same hill twice and compare results.
     
  2. raleighnut

    raleighnut Guru

    Location:
    On 3 Wheels
    TBH on my trike with a throttle I try and just balance the assist between pulling and overheating (laboring) the motor but I've got a front wheel motor.
     
  3. Pale Rider

    Pale Rider Guru

    The wattage rating of the motor is 'nominal', not least because all motors give more peak power when it's demanded from the controller.

    Your fully road legal Shimano Steps motor will peak at about 700 watts.

    Thus watt rating is all but meaningless and difficult to measure for the purpose of the legislation.

    Several quite pokey motors are sold with '250 watt' stickers on them, and you can buy such stickers online.

    What is not negotiable is the speed cut-off of 15.5mph/25kmh, plus or minus a small allowance for error.

    It's also easier to check because measuring speed is simple compared to measuring watts.

    If the motor is still assisting at 18mph, it's not road legal.

    As regards economy, the lower the assist setting and the harder you pedal the less power you will use.

    There's also aero benefits to going slower, wind resistance takes up a more and more power the faster you go.
     
    raleighnut likes this.
  4. OP
    OP
    BilboSmeggins

    BilboSmeggins Über Member

    Thanks for the reply. You’ve certainly cleared up the first question, cheers. I think we are at cross purposes on the 2nd question however . I realise that if I contribute more, it eases the burden on the battery and motor. What I meant was that, say my legs were to push a consistent 200 Watts in both scenarios, which would burn the most juice? A high powered boost, for a short spell, or an eco setting, for probably 3x the duration covering the same distance?
     
  5. jann71

    jann71 Über Member

    Location:
    West of Scotland
    On mine (Bosch) it gives an estimate of how long you have left on the battery based on current pedalling and mode.

    A short burst on the highest boost uses way more battery than if you did the same 3 times on eco.

    Hope this helps.
     
  6. gbb

    gbb Legendary Member

    Location:
    Peterborough
    And on the Crossfire /Suntour system the display can show more accurate battery remaining figures, rather than the vague 5 bars on the battery itself. Perhaps yours does the same ?
     
  7. OP
    OP
    BilboSmeggins

    BilboSmeggins Über Member

    Thanks all :smile:

    My system display will show projected ranges, but not actual battery percentage remaining. Went out yesterday, and covered 43 miles, with over 3200 of feet elevation, and got back with 2 (of 5) bars still showing. I shall seldom push the battery any harder than that, so I think I can relax a bit.
     
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