Here's what I found out before buying my Pie last week.
Assuming you're a noob like me. First, a bit of background on electricity.
higher voltage = higher speed
higher amp output = quicker acceleration and hill climbing ability (torque)
Why?
Water is comparable electricity (bear with me)
Imagine a hose pipe is like the electric cable coming out of a battery and the flowing water is the electric flowing to your motor.
Voltage (V) is comparable to the *pressure* of a water supply which is supplying the hose. More pressure means more voltage
amperage (A) is the thickness of that hosepipe and constitutes the *amount* of electric flowing out. More thickness = more power.
now, imagine the water coming out of the hose is falling onto a water wheel and the water wheel is turning at a constant rate.
Now, imagine turning the tap full blast (increasing the voltage) and see how how this affects the water wheel -it goes faster.
Now change the hosepipe to a firemans hose which is thicker (bigger amperage) and you will quickly see that even if there was just a trickle of water coming out, the force of this water would be such that the wheel would move slow but trying to stop the wheel from turning with your bare hands will require some effort.
These same principles of voltage and amperage apply to the golden motor and more specifically, the battery you're going to use with it in the same way that water pressure and thickness of pipe affects the water wheel in our water analogy above.
Amperage output of a battery depends on two things.
1. your battery rating (measured in C)
for example. a 12AH battery rated at 1c just means that you will draw 1c*12AH which is 12 amps constant power.
A battery at 3c will output 36 AMPS (3c*12AH) constant power.
There's a risk of a LifePo4 battery failing under this constant heavy load if you go over it's rating - so it's best to stay within the 1 to 2c range if you want to extend the longevity of your battery above 1000 cycles. (this is a gray area because of the relatively newness of this technology i.e. no one has actual proof how long they will last in actual practicality - maybe more maybe less)
The GM batteries and the controller won't extract more than 2c so you're safe with this.
2. Your controller.
The MP internal Controller is set up to take just 16A of power and the external controller around 20A (no one seems sure of the actual output as it varies only very slightly from controller to controller) which is more than enough for commuting and trips to the shops.
So how does this voltage and amperage translate into how fact am I going to go?
What does this mean in terms of actual speed on the road?
Depends entirely on the battery you you get but as a guide:
(36V X 16AH / 250W ) X 32KPH = 73.728k range
or
(48V X 12AH / 768W ) x 45KPH = 33.75k Range (this is minimum because you won't be producing 768W while going on a flat - maybe only 300W ish - depending on wind, weight of rider but the more speed you do the bigger the wind resistence and this will drain your battery far quicker because you're neededing more amps to push your portly figure through more air)
I've yet to see this formula put into an exact science and have it applied to the GM but this is only a rough guide and is somewhat taken from the goldenmotor.ca website.
Magic Pie Pro's and cons:
Pros
- speed and watts is determined by battery size (other motors are fixed)
- can be run at 24,36, 48 volts (and new ones upto 96v)
- 24v goes about 20 kph performs like a 250 watt motor
- 36v goes about 35 kph performs like a 500 watt motor
- 48v goes about 47 kph performs like a 1000 watt motor
Cons
- speed is not considered to be street legal above 24v in Canada - above 200W in Australia - and for you in the UK, Basic regulations state that the bicycle must be ridden by someone of at least 14 years of age. Electric bicycles in the UK must not contain a motor of power exceeding 250watts. The bicycle must also be restricted to 15 miles per hour (24 km/h)and a certain speed in the UK/europe. if you get stopped you potentially could get done for driving a motor vehicle without tax insurance, MOT and license but will most likely have your bike impounded. (yes this sucks) but is still a legal grey area because bikes will go over 15mph even without a motor. Even if you have a cutout at 15mph for your motor and then you start peddling, then it will be assumed thsat you're breaking the law which just says that the law is defunct and no prosecution could possibly arise from this unless they take your bike to be tested at the DVLA bike testing facility (which at the time of writing, does not exist) Source:
http://en.wikipedia.org/wiki/Electric_bicycle_laws#United_Kingdom and see this:http://www.pedelecs.co.uk/forum/electric-bicycles/6210-help-police-impound-bike.html The best way to stay legal is to use a 24v battery in the UK but you will have grannies in wheelchairs overtaking you.
- relatively new technology
So, defunct and useless laws that are designed to keep you dependent on oil aside, How powerful is this setup?
Power output is measured in Watts and is calculated by Voltage * amperage
So a 48v battery taking in 16Amps (internal MP controller) of continuous power will produce 769Watts of power. After losses (say 80%) in the motor etc output onto the tarmac is in efficiency of
will be 614 watts
a 20 amp controller will facilitate 960W at 48v and 768w onto the road after losses in the motor.
To put this into perspective, Lance Armstrong will pump out about 500w of power at his anaerobic maximum while doing the tour de France. (yes, it would be technically legal to tie a lance to your bike and do 40mph)
Don't for get that the wattage of the motor is really only the maximum that it's rated for - some people have changed their controllers and batteries and achieved over 3000w of output but the stains and stresses of doing this over the long term may damage the motor but from what I see on here, they are numero uno in china when it comes to robustness and over engineering it won't be covered by a warranty if you do this and screw it up.
GM have sold over 9000 of these motors and only a small proportion have died (going off the posts on here) and most of those are with people who've modded their setup.
Main areas of contention are the controllers that seem to blow if you connect mass amounts of amperage to it e.g. >100A but the default setup should last you years imo.
Getting in touch with GM can be a pain in the @rse (it seems) but it is 100x better than say buying of an ebay seller who at the first sign of trouble will just disappear. GM are the manufacturer and will strive to protect the reputation of the company i.e. you won't get ripped off and there will be some sort of guarantee if you don't modify the kit and use a GM battery.
one thing about GM is that there's a bunch of great people on this forum that'll help out any issues you have so you don't need to even get in touch with GM except for getting a replacement this or that.
Lastly, I'd check the cost of a pie in the UK against the true cost of a GM directly from China - including the postage which will even out the price to be about the same.
So if you want service then a local distributor would be the best option because you're in the same timezone and speak the same lingo - and the same GM guarantees come with the product.
Hope this helps.
