Mac 6T 20" wheel, 40 amp controller.. good idea?

[Raged]

I ride a 20 inch folder with a 10T BPM and 20S battery + 20A 6x4110 fet controller, which is similar to a 6T MAC with 12-13S (48V) battery. The bike does about 30-33mph and climbs with ease.
HOWEVER, the rear positioned motor and battery make the bike severely unbalanced. It is quite unpleasant and dangerous on takeoffs, even at 20A it wants to lift the front off the ground if I don't lean forward, and there is generally low front wheel traction. I haven't crashed this bike yet, but had some close calls. All of this is made worse by the fact that is is a production push bike with short chainstays. Had it been made with longer ones, like most e-folders that need to accomodate a battery, I could get away with 25A (equivalent to 48V40A @ 6T) for even better take off, and have a safer, more stable ride in general due to increased wheelbase. As it is now, the bike is quite scary. Therefore I strongly recommend getting a used e-folder with extended stays and give it a new motor+battery.
I had the same motor in a 700c wheel and while it had less torque, it was a safer ride, less noisy AND more efficient at moderate speeds due to less non-copper motor losses. To lower the noise, I suggest a sine wave controller.

This is the arguement to put the battery pack in the middle of the frame if possible.... I was lifting the front on takeoffs with a MAC10T and 29" wheels on 40A. The MAC motor on 40A is almost a scooter.

 

[miuan]

when you are converting a folding push bike, your possibilities for battery placement are rather limited.

 

[worldpax]

Jetstream has a nice flat sided frame. You could clamp a platform to it so the battery sits right behind the headset. Have to experiment as to whether above or below the frame would work better. Crap, now you have me wanting to build my own. Goodbye quarterly bonus check.

 

[RAT TAT TAT]

I agree with frame mounting the battery.

I was looking at mounting it below the tube, but I am going to have an issue with front wheel/pedals clearance and shifting of the battery with this 48v20ah battery.
Either way, some sort of mount or clamp to the flat sides of the tube will be needed to prevent the movement like worldpax said, if it is tube mounted.

There are a few pics on I found of a mid-drive jet stream where the battery was mounted below, looks like balance would be perfect.

My friend has a Dahon Mariner with the equivalent of a 10T mac and has the battery (same 48v20ah that I ordered) and controller in a small plastic toolbox on his rack in the back.
It feels pretty good, but I think the added power in this build might take away that option.
I imagine however, that the shock might absorb a good chunk of the kick ?

I had to cash in my vacation pay for this build, so I feel for you pax! lol

 

[izeman]

Most noise I hear is from the square wave controller. The 9c whine. A sine wave controller is much quieter.

i can confirm. even though ppl say sine wave make the most sense on big DD drives, it's absolutely also true for geared hubs. i have a kelly kls-s installed on my bike and it's WAYS more quite now. it's strange to ride as your brain thinks loud=fast and you think you're slow because the noise is missing now. but that's absolutely not true.

 

[Lupulin]

I love the idea of this and am considering something very similar. I am just looking for a hub motor that is compatible with a spline cassette. I don't want to be limited to 7 gears on the rear cassette. Any ideas?

Lupulin

 

[d8veh]

I love the idea of this and am considering something very similar. I am just looking for a hub motor that is compatible with a spline cassette. I don't want to be limited to 7 gears on the rear cassette. Any ideas?

Lupulin

Bafang CST, Bafang SWX02C, Q128C, Falco, Bionx, Heinzmann, MXUS MX01C, Xofo XFK, Xofo XF-V(K). There's loads of small cassette motors too, like Q100C, Keyde, Bafang SWX01C and MXUS XF08C. Take your pick.

 

[cwah]

Very excited!
Ordered some Shinko SR714's (16x2.25)

Having some faith that I can get these to work, as they would be ideal for the higher speeds and I can worry less about a flat..

Do they fit 20" wheel?

 

[goosenoose]

Edit...oops, didn't realise this thread was so old.

I'm considering doing this same things except with a DD hub (ie leaf motor, 1500w) for the regen and ebrake. Anyone have experience or issues with their full conversion kits (can the controller take a 52v ...40 amps continuous?) Or should I source the motor alone and get the controller and accessories along with the battery? (Ordering 52v 23ah battery from e3emv)

Ah... And would ordering a faster wind (eg 6 or 4t) make it less prone to wheelies on start? I don't have too many hills to worry about here in St Louis