Is there any other motor than 902 that has low freewheel resistance?

[Giuliano]

Hi,

I'm assembling my first ebike kit and I'm undecided to what kit should I purchase. Let me give you some contexts first.

I wan't to bike to and from work. In the morning I must to bike 9km to work. I don't want to be sweaty when I get there and that's the reason why I wan't to install motor. I have 26" wheels on my bike and I'm average height and weight. Now important part is that after work I'll be biking 17km to home and I don't wan't to use help from the motor on that trip. This is why I've decided on 902 PRO, as recommended on the goldermotor.ca website.

Unfortunately this motor is out of stock now, and I also have some doubts regarding the power of this motor as well. Is there any other motor I could consider that would freewheel with little to no resistance?

[Bikemad]

Hi Giuliano andto the forum.

If you don't have any steep hills the Smart Pie would be a good choice as it is just as fast as the Magic Pie on the level but is a lot smaller and lighter and does not have the very noticeable residual drag that the Magic Pie has.
If you're used to pedalling lots, it should be adequate to assist on slight inclines without making you work too hard but it does not have the hill climbing performance of the Magic Pie.

The Magic Pie 4 and Smart Pie 4 are incredibly quiet compared to the earlier Pies but I have not heard a 902 PRO motor to compare them to.

Another alternative would be to use a pair of the minimotors. These minimotors have an internal unidirectional clutch to virtually eliminate the residual drag of the motor when you are not using motor power, but the internal gears tend to be quite noisy.

The Smart Pie 4 would probably be my first choice for your specified use as it is compact, lightweight and virtually silent under power, plus you wouldn't need to find somewhere to house an external controller and the additional wiring that goes with it.

Check out my review of the original Smart Pie for more information, but please note that the newer Smart Pie 4 with the vector controllers does not make the growling noise under power that the original motors did, in fact there is no difference between the very slight spinning noise of the motor whether it is under full power or coasting with the throttle released.

You can hopefully hear just how quiet the Smart Pie 4 is in this video.

Alan
 

[Giuliano]

Thanks Alan,

Smart Pie 4 it is. I've done some research as well and got to the same conclusion as you. I'll probably make a purchase in the next few days once I decide on batteries. Having said that, may I ask another question?

I would like to build my own battery pack. I have this charger http://hobbyhobby.com/store/product/347715/44176-X1-MF-Multifunction-AC-DC-Charger/ and I was thinking of purchasing 3 batteries like these http://hobbyhobby.com/store/product/329276/LiPo-Onyx-3S-11.1V-5000mAh-25C-Soft-Case-TRA-Plug/. I would build a harness to charge them all at a same time.

What do you think about this idea? Would this charger work? Any other recommendations?

[Bikemad]

That charger would work, but it would probably take around four hours to fully charge all three packs from empty with the 55W charging output available when running from mains power, and don't forget that LiPo batteries should never be left unattended while charging!

Those LiPos seem very expensive to me, but I'm a bit of a cheapskate and prefer to use these cheap and cheerful but better protected Turnigy 4S hardcase packs to build my DIY 29.6V 5Ah 8S packs:



Which fits very neatly into this compact frame pannier too:



If only the controllers would allow a 16S LiPo pack to be used.

If you wanted a bit more speed, you could use three of them in series to make a 44.4V 5Ah 12s pack and simply connect them in parallel to charge as a 4S3P 15Ah pack, but you would also need to use a special balance lead adapter to ensure all the cells were monitored and balanced during the charging process.

I have a couple of iMax B8 LiPro Balance Chargers and a dual output 350W power supply so I could theoretically charge two packs @ 150W each simultaneously, but I usually just use one charger to charge all 8 cells in series at 150W using a home made balance lead adapter.

Whatever you decide to do, make sure you fit a suitable fuse as these LiPo packs can really deliver some power if you make a mistake while connecting them:





Alan
 

[Giuliano]

Thanks for the detailed reply! I was just considering those batteries, although they are very expensive. I guess it's a Canadian way of pricing. Luckily I'm in Toronto so I'll probably jump to the border and get them from the US HobbyKing. I'll let you know how it goes.

I have some experience with RC Airplanes. That should help little bit with making battery pack. I have balancing board that came with charger so there should be no additional cost to make this work.

Now, let's order that motor and batteries!