Assisted mode / gear shift conflict

I've just bought this Powacycle Prague.

New model, improving on older Salisbury / Windsor by adding extra assisted mode(s), but I'm not sure, possibly the problem was there for older models as well.

 

I have 3 assisted modes, say High, Medium and Low. High takes more power from the battery and it's limiting to 15 mph, the law, fair enough.

 

On High if it's flat and no particularly strong head wind all the gear shift is useless. I'm on 6 (highest speed, small cog on the back wheel) and pedal in void, no resistance / reaction whatsoever! This is not only annoying and useless but possibly dangerous since all my body weight is on saddle (no support on legs), so my spine will take all the bumps in the road.

 

Arguably I could switch to Medium and take less power, save battery and do some exercise. Sounds great, only this will not allow me to reach 15 mph for some obscure reason even if I put allot of effort into it.

 

Is that what one should expect from an electric bicycle or I'm just unlucky?

 

Any comments appreciated,

Cheers,

Adrian

This is a common complaint with e-bikes Adrian, basically due to gearing for the 15 mph legal limit which for many is too low, even in top gear. If you can use higher cadences and spin fast enough, there's nothing to stop you pedalling beyond the motor limit of course, many do when they have the strength. With some machines using hub gears, changing the rear sprocket is a quick solution to raising the gearing, but this is not as easy on yours. Changing the chainwheel for a larger one would seem to be the answer, but the Salisbury had a special kind of pedelec sensor on the back of it which may be on your one as well, complicating things.

 

Alternatively, you may be able to obtain a different rear freewheel with a smaller top gear sprocket to raise the top gear a little.

I would say that it depends how badly you need a higher gear. On my old Powerbyke Euro, I used a modification copied from what someone else had done on this forum. I bolted a larger chainwheel onto the outside of the existing chainwheel . Search on ebay until you find one with the same number of spokes, five in my case. My original had 5 small bolt holes to fit a chainguard, so I just enlarged these. The result was all I hoped for.

>> flecc says: "If you can use higher cadences and spin fast enough, there's nothing to stop you pedalling beyond the motor limit of course, many do when they have the strength."

 

It's not about strength here, is it? I can spin as fast as humanly possible because there is no resistance in the pedals, but exactly because of that there is no output; there is no effort put in, where the extra power is supposed to come from?

 

But more importantly... Say that I accept at the moment that in the High power assist mode I won't be able to push over the motor speed. What about the Medium mode? Is it normal that no matter how hard I push (even downhill!) I won't go over some 10 mph, perhaps less? (I haven't measured yet, but I'm sure it's far less than the speed I get without any effort on High mode).

 

Adrian

It's odd about not being able to pedal over the assist limit.

 

Do both wheels turn freely? What are your tyre pressures?

Same here, I'm puzzled by the description and assumed you meant unable to pedal faster. If the chain is still on the sprockets it must still have transmission to the rear freewheel. I can only think that the chainwheel pedelec unit is disconnecting the chainring from the cranks as you get up to speed, leaving it spinning free. If that's the case, no it's not in any way normal and must be a fault.

Sorry for not being able to describe it, my vocabulary is limited when it comes about mechanical things.

 

Let's concentrate on one aspect, pedalling in High mode and ignore the Medium for the time being. That means maximum of assistence from motor. No wind, flat terrain, start pedalling, the motor kicks in, you switch to a higher gear because it's too easy, only you have already got to the highest gear (6) and it's still too easy. So easy that you can almost compare it with peddaling after your chain has fallen off. Is now clear what I meant by pedalling fast and no resistance?

 

flecc says: "I can only think that the chainwheel pedelec unit is disconnecting the chainring from the cranks as you get up to speed, leaving it spinning free"

 

That sounds terrible to me. You mean mechanically disconnecting? I somehow believe it's not that bad. Would they do that to limit the speed?

 

I kind of feel what could happen, they intentionally designed a small chainring so that once you got to the max speed you don't have any efficiency, would that make sense?

 

If that is clear, I'd move back to Medium mode, because that I still can't understand.

 

Thank you for your patience,

Adrian

I think I'm understanding now. Yes, they are mostly undergeared, partly in deference to the e-biking laws and partly because a high proportion of e-bikes are sold to elderly people of very limited cycling ability. If you use high mode it will be ridiculously easy to pedal for anyone capable of inputting a decent amount of pedal power, but the high mode is intended for hill climbing, not for normal use everywhere. Many e-bikes have three power modes, Eco, Normal and High, and a fit rider can use Eco which is set at half the Normal power level. I'd say just use a lower power setting that does leave you something to do, except you say that doesn't allow the power to continue to 15 mph. That's not true of all e-bikes but may be by design in yours. It does sound odd though, so possibly check with Powacycle if that lower top assist speed is normal in the medium power mode.

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Edited July 31, 201213 yr by flecc

That was what I would expect, thanks for confirmation flecc. It all make sense with speedlimit and older users, still perhaps the Normal mode limitation is a step too far if done by design.

I have already contacted Powacycle, let's hope they can do something about it.

 

Many thanks to all the advicers here,

Adrian