Convert MP3 to MP2?

[OCD]

First time posting but long time e-bike builder.

This summer I decided to try out two things, the GM MP3 and e-drift triking. I bought the 20" cast wheel MP3 and put it on the front of the trike I built. LOTS of fun, it's a blast to ride ( https://www.youtube.com/watch?v=zMbThG7F_bw ) BUT, I find after about 20 minutes of sliding the controller cuts out, you turn the key off (at the GM 48 volt battery) and turn it back on, it seems to reset itself and carry on until it shuts down again. I'm assuming the little MP3 internal controller is over heating. I have a 3000 watt, 80 amp controller I'd like to run instead, that should have more than enough power for sustained drifts. I haven't taken the MP3 apart yet, can the MP3 be easily reworked to use an external controller or do I have to buy an MP2? 

Any advice would be appreciated

(The other) Alan

[Bikemad]

Hi other Alan andto the forum.

That trike is nicely built and certainly looks like it is a lot of fun to ride. Although after seeing you video it would be much better to relocate the footrests so they are mounted on outriggers from the frame so you don't have to keep dangling your legs in mid air.

Is that a 3.00-16 motorbike tyre you've got fitted to that 20" Pie?

Regarding the controller conversion, the MPIII is relatively easy to convert to external controller, and the wires on the MPII external version are probably too thin to handle 80 Amps.  Here are some photos showing GM's modification to the wiring on the motor to allow an external controller to be used:





You might want to use some heavier duty phase wires than the ones shown in the above photos if you're going to be pushing 80Amps though it.

I'm looking forward to seeing a video with all three wheels drifting instead of just the rears with all that extra power and very little weight over the front wheel.

Alan
 

[Morgen 3Eman]

I love it!

I did the conversion and it was no problem, except for physically locating the controller and wiring.  That was a pain in the neck. 

TTFN,
Dennis

[OCD]

"Although after seeing your video it would be much better to relocate the footrests so they are mounted on outriggers from the frame so you don't have to keep dangling your legs in mid air."

I could, but it's more challenging trying not to run over your feet (lol). I have seen outriggers on a couple of gas powered rear wheel drive trikes, it looks kinda goofy and I think you'd be in danger of catching the pegs.

"Is that a 3.00-16 motorbike tyre you've got fitted to that 20" Pie?"

Yes, a 16" motorcycle tire fits on a 20" bicycle rim if it's wide enough. A number of high powered e-bikes are built with scooter tires. A bit heavier of course but much more tread to burn through with little chance of a flat.

Alan are you showing a converted MPIII or is that a pic of an MPII? Can you buy the harness as shown or would I have to make my own?

[Bikemad]

Alan are you showing a converted MPIII or is that a pic of an MPII? Can you buy the harness as shown or would I have to make my own?

Here you can hopefully see the obvious difference between the MPII on the left and the MPIII on the right:



The pictures I posted previously were of an MPIII that was modified at the factory, but I don't know whether the wiring harness is available separately or not.  As with the external MPII harness, I suspect you would require thicker wiring to carry 80 Amps for sustained periods of time.

Presumably you will be fitting a heavier duty battery to cope with the demands of the controller, as the GM battery is unlikely to deliver that amount of current unless you bypassed the BMS (which would allow the cells to be overloaded, resulting in permanent damage).

All you need to do is extend the three phase wires using suitable cable, along with the five thin wires from the hall sensors using a length of flexible network cable etc. (not required if you are using a sensorless controller) and fabricate a circular cover plate from some 3mm aluminium for the cables to pass through and simply bolt it in place of the old controller.

Alan
 

[OCD]

It's all very clear now. I appreciate the advice. Do you think the C rating of the GM battery will be too low? I may have to switch to LiPo then.

Thank you 

[Bikemad]

The 10Ah LiFePO₄ cells are rated for 30 Amps continuous and 50 Amps peak current, but I seem to recall that the BMS is limited to 30 Amps. 


I have carried out a quick check using my modified MPII and my new 48V 10Ah GM battery only delivers 31.21 Amps maximum @ 46V (1,433 Watts) yet my knackered 4.5 year old 14S 5Ah LiPo pack (without a BMS) is able to deliver 38.53 Amps maximum @ 42V (1,618 Watts). So I guess the BMS on the GM battery is holding back the current.

I used the same LiPo pack (when it was still good) to achieve this output using my tweaked internal controller on my original MkI Pie just before it also died:



The lighter weight LiPo batteries are great if you know what you are doing and take good care of them, but they can also be very dangerous if you don't.

Alan