Possible?: Dual Pies with Different Controllers on GM 48V

[Pwd]

Hello, I've got quite a few questions in regards to upgrading my bike:
I would like to get a rear Magic Pie (I currently have a front one) to make my bike a dual pie setup. I have the 48V 12Ah GM battery.

Can anyone verify if there are any amperage differences between the internal pie controller and the external pie controller? If someone could provide me with the actually amp readings of the external and internal controllers that would be great! (max/continuous)

I have also been considering purchasing an Infineon 40A Controller if there is no difference between the GM internal/external. If I did buy one, would my battery handle both the pies? (One with an intenal and one with the 40A Infineon)

Thanks in advance, I can't wait for bike season again!

[MonkeyMagic]

Hi PWD

You can run dual drive safely on INTERNAL controllers only.
Internal controllers will draw between 15-20A at times continuous.

GM website rates the battery as 20A continous current. I can vouch to say that it can handle 30A continuous - and the only way I clarified that was to buy the exact same batteries GM use (for a failed pack....)

So here are your choices

1. Dual drive with internal controllers. Retain your 48v GM12Ah battery. Your range if used sensibly will be slightly greater due to running both wheels at once, expect double, near triple your take off speed - and I am yet to find ANYONE not happy with a internal dual drive setup

2. Buy the external wheel, plus controller (infineon whatever) and be up for more $$$$$ however, you will launch like a rocket but will need another 48v battery and would be juicing the power constantly. Sure the bike will fly, but you have reduced your range. It's up to you.

Honestly, and speaking from personal experience - I would suggest sticking with the internal controller for simplicity sake.

Anyway don't even try running dual drive with either of them external controller, using that battery. You will risk damaging the BMS and it will cut out on a hill or takeoff above I believe 45-50A max is what that battery can peak.

Description of cells attached (try adding the cost for the whole lot, plus cell holders, plus key switch, BMS etc. etc. etc)

GM packs are FANTASTIC value, and are built with terrific quality now.

You could say this to yourself "Okay I will go with the internal controller. Then maybe down the track I'll get another battery and 2 controllers and make them external dual drive"

But I assume you will never think that

Good luck with your decision, hey what size wheels are these>?

Cheers

[Pwd]

That seems to make sense. I am limited by my battery max current (and funds haha).

So the safe bet is to go for the internal controller pie as the rear hub. Seems like the logical decision for my setup since in the long-run I'd save money not buying another battery and will be happy with twice? the torque. Also, I don't exactly have room for external controllers etc...

Thanks for the insight, I'd rather have a cost effective, safe and reliable rig with good performance than an expensive e-bike with unpredictable performance/reliability. BTW, they are 26 inch wheels. (I should probably make another order from Gary soon so I can be ready as soon as the streets dry up and the weather gets warmer.) So when I order the rear pie, what will it come with and do I need to order the freewheel/remove tool to ensure I can still have a 6 speed cassette back there?

Cheers! 

[Andrew]

I believe Gary runs one external and one internal controller on his dual pie setup.

I run two internals. Adding the second pie will transform your bike. I run one GM 48/12 battery on the dual pies and have not had any problems.  you will need a "freewheel" - a cassette is a different kind of cog assembly, the freewheel will have to be ordered as an extra, it does not come with the rear pie kit. To attach a 6 speed freewheel you will not need any tools, it can just be turned/threaded on by hand. if you need to remove a shimano freewheel make sure the removal tool is an 'UG' fitting and not an 'HG' fitting.

If you have a standard 135mm rear frame width you can fit a 7 speed if that is preferable

[MonkeyMagic]

Hey Andrew, Gary also runs 2 x batteries (I think 3 including the Bob trailer!!)

So I don't think any of them external is a good idea.

I'd just stick to the internal controller, you're not gunna get any more speed out of it anyways

[Bikemad]

Gary also runs 2 x batteries (I think 3 including the Bob trailer!!)

The Pie on Gary's trailer was just my wishful thinking, brought to life with the aid of , unfortunately it's not really on his trailer, but it may be one day!



Alan
 

[GM Canada]

Boy my ears are buring on this thread

I do run a front external pie and a rear internal pie. The wiring is no different and it is as easy to wire two internals, two externals or one of each. As mentioned I have two batteries as well. it is not nessasary to have two batteries for a dual pie setup, but it is a law of phisics that if I want to go as far as someone that is half my weight I need twice the battery power. I have run them with one battery to each motor and the two batteries in paralel. Either way works fine. The third motor does seem interesting as well, but that is somewhere down the road after if finish cleaning up the wiring on my just built dual mini motor setup (which is wired the same way you would wire a dual external pie setup) or maybe after I build a recumbent trike. Yes that is my next dream 

Gary

[Bikemad]

The third motor does seem interesting as well, but that is somewhere down the road after if finish cleaning up the wiring on my just built dual mini motor setup.

Well a Tri-motor (triple minimotor) would certainly be interesting, more power for hills and virtually no drag when coasting.

Gary, with all your wheel building experience, I'm sure you could radially lace a minimotor into a 16" rim, even if you just turned it on when needed to help push that trailer up hills at slower speeds. A 16" wheel with a geared motor should provide some really useful slow speed torque.

I reckon it would provide up to a 75% increase in both acceleration and hill climbing below 10mph, but even at full throttle, it would probably just be free-wheeling at higher road speeds, unless you decide to run it on 60V! 

It would be nice to have it switched by a load sensing device, so that it would automatically join in when the 26" wheels were working hard on steeper hills or accelerating away from a standstill.

Alan
 

[GM Canada]

That sounds so damn interesting. A freewheeling mini motor on the trailer! It would be very usefull in both my dual motor setups, one mini makes 2 tri drives. Ok thats it, i'm shedding al my credit cards. Oh yeah, everything is free from storage!

Gary

[Bikemad]

Oh yeah, everything is free from storage!

That's very kind of you Gary, just send me a copy of your inventory and I will decide which free items I would like.
No doubt you'll be giving me at least 95% discount on the shipping as well!

Alan
 

[GM Canada]

I am Still thinking about this. I have quite a few different sizes of spokes and could probable do it with the original rim but I am not sure the original rim would hold up to a motor and all the weight I carry in that trailor.

Gary

[Bikemad]

I am not sure the original rim would hold up to a motor and all the weight I carry in that trailor.

Gary, because of the position of the load in relation to the wheel, only about half of the load would be acting upon the wheel (see attachment below).
If you were hauling 200lbs in your trailer, then your trailer wheel would only be supporting ~50% (100lbs), and your bike's rear axle would be carrying the other 50% (100lbs).
That 16" rim will be able to withstand at least twice the above mentioned load, but I doubt that you would want to carry 400lbs in your trailer.  
If you kept piling more and more load into your trailer, I would expect the trailer frame itself to fail well before the rim (or wheel)!

On the shrinker, about 70% of the rider's weight is acting upon the rear axle, so how much load is acting on that tiny little rear wheel when a large adult rides it? A great deal more than your trailer wheel is ever likely to experience!

Alan
 

[Bikemad]

I have quite a few different sizes of spokes and could probably do it with the original rim

Gary, I've just noticed that your rim only has 28 spokes, so don't start ripping it apart!
You would need a 16" BMX rim with 36 holes in order to accommodate the minimotor.

Alan
  

[GM Canada]

I have quite a few different sizes of spokes and could probably do it with the original rim

Gary,  I've just noticed that your rim only has 28 spokes, so don't start ripping it apart!
You would need a 16" BMX rim with 36 holes in order to accommodate the minimotor.

Alan
  

Haha, you have been putting more thought into this then I have. Good observation though. Thanks..

Gary

[Pwd]

For the record, I just pulled the trigger on a rear Magic Pie (internal controller). Now I have to wait for the snow to melt and my package to arrive. In the mean time I'll be reading everyone's write-ups on the dual-pie setup and I'll be doing a mock-up for a torque arm.