Gear ratio and power use/battery life

[Bri-72]

Only had ebike (focus Jam 2) a few weeks so still getting used to it.

Despite experimenting I still am not sure whether it’s better to go lower gear higher cadence or higher gear lower cadence. From the perspective of minimising power output/battery use. Or maybe it makes no difference.

I find the shimano system almost has too much power (even in eco mode), so trying to experiment as to what gearing is best to balance my power vs motor assist. And that’s from someone who rides very hilly terrain (Highlands of Scotland).

While I can customise the power mode, I can’t lower eco or trail from the defaults, I can only increase them.

I’m not a technical minded person at all, so really don’t understand what effect gearing and cadence has on the motor assist.

 

[Eckythump]

If you are trying to get duration from the battery keep the power bar along the bottom of the display and minimise the amount of time it is climbing up the right hand side.
Lower gear and spinning keeps things running longer.

 

[Bri-72]

Is what I thought but the display tends to suggest a lower cadence has less motor assist. So on a flat or not too steep section, slow and steady seems to use less power per display than high cadence.

 

[Eckythump]

I find the opposite, I tend to put more force on the pedals if I go slow and grind. The power meter of the motor sees this force and applies more assistance potentially up to the maximum level.
If I drop to a lower gear and start to spin fast I cannot apply the same force so the motor assists less.

 

[steve_sordy]

I went on a demo day about 3 weeks ago and more than one guy told me to increase my cadence. It is more than just eking out the energy in the battery, apparently some motors react more smoothly with higher cadences. I told the Giant rep that I was changing gear to stay at my usual cadence of about 60 and that the motor (modified Yamaha) was pulsing. He told me to use a cadence of 75. I found that the Specialized Brose S motor was doing the same (pulsing), so may be a faster cadence would have worked for that too. But the bike with the Shimano Steps was fine, which is why I chose that one. The Focus Jam2

 

[steve_sordy]

I find the opposite, I tend to put more force on the pedals if I go slow and grind. The power meter of the motor sees this force and applies more assistance potentially up to the maximum level.
If I drop to a lower gear and start to spin fast I cannot apply the same force so the motor assists less.

It assists less per rev, but more frequently!

That is the laws of physics in action. As long as you use the correct units, torque x speed = power. And torque = force on the pedal x the crank arm length. It should not really matter whether you use low torque and high speed, or 25% higher torque with 25% lower speed because the power drain should be the same.
I don't KNOW this for sure, but I used to be an engineer decades ago and I'm taking an educated guess that different motor and battery combinations work better and deliver their power more smoothly in different parts of the rev range. Or maybe it's all in the software! We already know that different motors give up their power differently, because the magazine riders say so, and those who have ridden a range of bikes with the various motors will confirm that.

 

[Eckythump]

You seem to be mixing a few things up here. The different motors are most efficient at different cadence rates. The original Yamaha worked well at the lower end Bosch at the higher end, Brose & Shimano somewhere in the middle.

All the systems give a ‘background’ assist level dependent on the mode you have selected. This you can usually adjust in the associated apps.

In addition to the background assist level the motors also ‘feel’ the amount of force you are applying on the pedals at whatever cadence you are doing. If you push hard on the pedals the motors sense this and add more assistance. If you start pedalling lightly the assistance will back off.

Shimano introduced Trail Mode which took the load sensing much further than had been done before and has since been emulated by the other motor manufacturers.

So the speed you go through the battery is mainly dependent on the assist level you have set, and the load you are putting on the pedals particularly if using a ‘trail’ type mode.

Glad you are enjoying your Jam2, I also like mine very much.