What to get? Magic pie or 48V 1000W?

[wheeleeboy]

So I'm a college student who just needs a fast ride from my house to the college, which is 2.5km away. The road there and back is flat with no hills. What type of conversion kit should I get? I've been reading about the Magic Pie but I hear that people have problems with it and it is not as fast as some of the older models. I was thinking about getting the 48V 1000W system found here: http://www.goldenmotor.ca/shopping/pgm-more_information.php?id=33&=SID#MOREINFO . Would this be a better choice? I don't need long runtimes but I do need speed. I also don't want the thing to break on me like I hear MP has on some. The MP is also more expensive. Ideas? Thanks!

[Mabman]

2.5k of flat road? You don't need a motor for that, just use a regular bike and leave a few minutes earlier.

[John-uk]

true mabman lol. Personally I would go for 72v with a 1000W motor and impress your mates as you go past at 35 mph, You could get away with a low cost lead acid low AH battery for that distance.

[Hardcore]

72v is alot of weight in SLA's

[John-uk]

hi hardcore. Yer wouldnt be practical on a bike were you were going to do big miles but for 5 k how many ah would you need ? 6 x small ones ?

[Hardcore]

if you get 6ah orso I don't think it would deliver enough amps, unless you get lipo's without bms, that's also cheap

[wheeleeboy]

how would I go about doing this 72V battery trick? I want to keep it simple and small

[John-uk]

Hi Wheelee boy. 6 x 12 v batteries in series. can be done easily and lots of people do it. but best to ask one of the more technically minded people on here for full details. BUT. ive seem it done with high quality rechargable power tool batteries.

[wheeleeboy]

Would it be cheaper to do it this way? Would it also take less space? Do you need a different controller? And would it do damage to a hub that takes 48V normally? Thanks!

[Hardcore]

hey, I got accros this website,

12 Volt 5 Ah/Amp hour Electric Scooter Battery
12V 5Ah/Amp hour Universal Power Group® model UB1250 electric scooter or bicycle battery. 1/4" tab connectors. UL® Approved. Includes full 12 month Universal Power Group® battery replacement warranty. warranty details
Replaces: All similar sized 12 Volt 4Ah and 4.5Ah electric scooter/bike batteries.
Size: 3-1/2" long x 2-3/4" wide x 3-15/16" high (90mm x 70mm x 102mm)
Weight: 3.2 lbs
Item # BAT-12V5A
Click here for more information on this battery.   BAT-12V5A
$16.95

it's 12v 5AH and cost 16,95
if you take six of them you get 72v and 5ah it would be 149,70 USD that's almost 100 EUR
you also need a charger.

[Bikemad]

Do you need a different controller? And would it do damage to a hub that takes 48V normally? Thanks!

Yes, you would need a speed controller which can handle 83V! (6 fully charged batteries @ 13.8V = 82.8V) as GM controllers are only rated for 60V MAX!

The 48V hub might just cope with 72V on the flat, but could suffer from overheating (possibly causing internal damaged) if it was forced to work hard for too long.

Alan
 

[Hardcore]

i think the hub can take more than 48v definetely
but I don't think you get any warrenty if u use more than 48v or more than 60v.

i read on the ES forum there was someone who makes controller for like 160usd, this could be an option for you as you need a 72 or more controller. I also think crystalyte controllers take up to 72v

[wheeleeboy]

Thanks for the help everyone. I think I could probably do this but my biggest problem would be taking a risk as to buying different parts and having something break on me, therefore = $$ lost. I think I'll take the safe route seeing as I have never done anything with ebikes and just buy a complete kit from GM. Thanks again!

[Hardcore]

i did the same but now i'm looking at a rc motor, that delivers 6kw and alot of Nm and rpm
i'm thinking of a turnigy motor and ESC but don't know how to connect to a throttle or so.

[Bikemad]

i'm looking at a rc motor, that delivers 6kw and alot of Nm and rpm
i'm thinking of a turnigy motor and ESC but don't know how to connect to a throttle or so.

You would need a separate 5 volt supply, as the speed controller does not have built in BEC, and could probably modify a servo tester to control the speed controller using a normal twist throttle in place of its potentiometer:

 

Fitting the motor would be your biggest problem:
Being an outrunner motor, the main shaft and the outer body rotate together and only the back plate (where the leads are attached) remains stationary, making it much more difficult to mount securely.
As this motor runs at over 6000rpm at 48V, it will also need some form of gear reduction to provide decent torque and a suitable top speed without overloading it at low revs.

Fitting this motor to a bike would certainly be possible, but it would take a lot of work to do it.

And don't forget you will need a suitable battery pack that can deliver 120Amps continuously!
Two 6S 5Ah 25C LiPo packs in series would just be able do this, but would only last for two and a half minutes at full power.

Four of these would give you 5 minutes:



It's not quite as simple as it may first appear.

Although someone has already done it:
Here's the video on YouTube

Alan