Price and advice for mid drive conversion

[Woosh]

1. Does this 'optimised' 15mph speed also mean you have the most efficient battery use (least amount of power wasted as heat at this speed - given you want as much oomph as possible)?

Very nearly. The yield in the sweetzone is between 80%-86%, yield peaks around 18mph but drops down to about 83%-84% where the power output is highest.

2. What about DD 28mph Spedelecs like the Stromer bikes. Any idea what the optimised and no load speeds would be for that type of implementation?

if they optimise it for 28mph then I guess noload speed would be around 35-38mph.

 

[Andy-Mat]

hi all.

looking at a specialized pitch tomorrow to get me back into biking. Light trails but mostly path and soft road use.
was thinking of making it a commuter on my 25 mile round trip daily work commute of 90% flat roads. The bike itself is a 2015 and used, but it's really cheap so.

I've been told mid drive is best really, and I'm aware of bafang being a very good setup. But I'm wanting to keep costs down as once I'm used to an ebike after a conversion I'd invest more in a better setup or a factory e bike.

what would I need, and what should I expect to pay? I'll be able to fit it myself, or certainly with the help of a mechanic relative.

thanks,

steve

Reply

Apparently, many secondhand bikes have defective batteries through ignorance, so make sure that you do a good long test drive before paying.
A new battery may double the price for a bike. Then it gets close to a new bike price!
Do expect a dead battery.....its the safest way.....
regards
Andy

 

[GLJoe]

< Q on Spedelec optimisation speed >

if they optimise it for 28mph then I guess noload speed would be around 35-38mph.

Ok, ta. However I would imagine that the motor characteristic design decisions for a 28mph max Spedelec would be different to a 15mph max bike.

Many people will be riding a 15mph restricted bike right at the (fairly slow and easy to control) cutoff limit most of the time, hence it makes sense to deliver best power around this speed.

However I'd have thought that a typical average speed for an Spedelec is going to be a fair bit less than the maximum. So you'd probably want the strongest power delivery to be at this lesser speed ... I'm guessing here ... maybe between 18 and 22mph? maybe a bit more. but you wouldn't want it to be TOO low, because at some point, the back EMF would reduce the available power, and you still would want the bike to give reasonable power for the occasional straight line blast at 28mph (and given wind resistance, you might want quite a lot of power here??).
Conversely, I imagine you wouldn't want it too high, because then you'd get winding losses at the low speeds
So I was wondering if you (or anyone) knew what the max power/noload speed numbers might actually be in real life? Seems a bit of a juggling act (and ironically, more so for an Spedelec than the very artificially crippled 15mph bikes!). I've always been curious on this one but have never come across people discussing the issue.
(and I've always fancied a Stromer, but haven't even SEEN one in real life, let alone owned one!)