P5

BMC Brand Brushless Geared Motor ( rear motor only )

24volt to 48volt 20amp

  Peak power output approx 700watts
on 48volt 20amp controller
Top speed 48volt in 26" rim 40km/hr hill climbing ability excellent

This motor is quite similar to the P4 motor in structure though is a larger diameter ( higher torque) and has been in production for a longer time. When this motor began to be used by ebikers it was quickly realised that it has solved what was a quite big problem for some years. There was a problem with having both high torque at low speeds whilst still having high top speeds. The geared motors that were on the market had reasonable torque for their era but not much top speed, and the non geared motors were lacking torque and efficiency at low speeds. One solution was to use a dual winding motor such as the crystalyte 408/4012 or similar.

But the very surprising result was the motor along with having very high torque at low rpm had a very high top speed, equal to or slightly more than the non geared motors when running on the same volts and amps. That was quite a breakthrough by the BMC company.

The motor type used is basically the same as found in the GL2 motor which is a higher torque design than previous motors on the market ( this style of motor is also found in fisher and paykel washing machines, they patented the motor design many years ago) but there is also a planetary gear reduction drive ( about 5:1 reduction) so the torque is indeed very good. Being a geared motor when the wheel rpm is  low  the actual motor rpm is about 5 times the wheel rpm, and so the motor efficiency is quite high good at low rpm ( brushless motors are generally higher efficieny when run at higher rpm).

At the moment it would be by far the best geared motor on the market that I'm aware of. The quality of bmc motors is very high, the alloy used to make the hub casing is very strong, and other components such as bearings are also good quality.
For higher power use metal gears are a better option to reduce wear. I can supply metal gears with the motors but the customer will have to instal the metal gears themselves, its quite a simple process to replace the gears.

There are a number of motors on the market at the moment which are basically the same structure as this motor ( and more will likely come on the market in near future). Though this particular motor comes from the original maker/factory that first released the motor design in around 2004. Over the years they have made modifications to the design to improve its quality/reliability. Its an extremely good sign when a company continues to develop/modify the  design to improve its quality. More detailed info on the different motors of this structure on the market here.
It appears there may be some retailers selling an old version of the motor and calling it a new version, below a picture so you can see the differences between the older style and new version.

To keep things simple I'll just refer to this motor as a 350watt continuous motor the company does make another version of this motor though ( 500watt with lower resistance windings sold as puma motor by teamhybrid uk and evtech usa).

Below shows a picture of the hall sensor board. The board is set in place with glue ( i've removed the board from its glued position in the pic below). The hall sensors are a big pain to replace if they need replacing, they can be replaced though without removing the board, but to replace in the exact same position as they come from the factory requires removing the board from its glued position.

The picture below shows the coils of the motor ( similar to gl2 motor and fisher/paykel washing machine motors). The motor is a 3 phase ac motor as are most hub motors ( the controller converts the dc battery current to ac). Each colour below represents a phase. It appears that within each phase 2 coils are in parallel rather than all in series. How the coils are connected changes the rpm and torque of the motor. BMC seems to have some very good engineers and the way the coils are connected seems to make for good torque but also high top speeds.

Dimsenions of the rear motor shown below. The motor will fit into a standard 135mm rear dropout width. A 6 speed cluster is suitable and comes with the motor, there is also a thread on the left side of the motor for a disc/drum or band brake.

Pic below purple lines represent bike frame, 135mm space is required.

Picture below shows the motor with a 203mm disc installed. Disc doesn't come standard with the kit but I can supply if required. Note that a 203mm disc needs to be used, smaller discs wont allow for the calipers to sit on the disc due to the side plate of the motor.

A couple more pics of the motor

The gears use a standard wheel bearing type grease, if intending to use metal gears and overvolt/overamp then  a high temperature grease will probably be better.

The ring gear is also quite unique  on the newer version motor( the freewheeling mechanism is located behind the ring gear) a special tool is required to remove the ring gear from its very large diameter bearing. The smaller bearing is the axle bearing.

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Freewheeling system :   means no resistance from the motor if your wanting to pedal without motor assistance,  but also means no regenerative braking. The motor has one continuous axle so it can withstand quite high loads ( some geared motors have the axle in two halves). The freewheeling mechanism is similar to that used in the P3 motor and seems quite robust.

The controller that comes with the motor is the infineon chip controller, its also quite interesting that it wasn't very long ago that there were very few controllers that would run this motor over 36volts ( due to the high rpm of the motor). In the past bmc was supplying ananda brand controllers with the motors but to get the most out of the motor infineon chip controller seems to be the way to go. Other controllers that will work with the motor over 36volts are the crystalyte analog ( older style) controllers.
 

Below is the original graph before extrapolating. The test was done using an analog crystalyte controller 48volt and 20amp max. On the original graph you can see the power output curve stopped recording when about 18amps was reached, the crystalyte controllers will usually go a bit over 20amps, the output power curve on torque graphs is usually a very symetrical parabola, anyway to cut a long story short I'm quite sure the test was cut off early and the torque will be somewhere over 50Nm stall torque ( a fishscale test would be a simple way to confirm the actual stall torque (see link),  will try as time permits to do fishscale tests of all the different motors on this site).

Overvolting and overamping: there is a limit to the thickness of wire that can exit the motor via the hollow axle on one side. Therefore overvolting and overamping pose some risk to burning out the wires that exit the motor. My suggestion would be to change how the coils are connected if wanting to go to higher volts or higher amps, using thicker guage wires would also be necessary. Also since the motor was initially developed as a 250watt continuous 36volt motor the freewheel may be under some risk of damage over time if used on higher power levels. So my view would be use on 48volt 20amp max. Also using on higher power levels would require using metal gears.Using at higher volts/amps would void warranty on the motor.

There is some possiblity that bmc will release a 1kw version of this motor, with components rated for higher power levels. It will be very interesting to see their next release.

Whats in the kit:
1. bmc motor laced into a rim ( some choice on rims suggest wide dual wall aluminium)( spokes used are thicker than normal spokes: 2.3mm dia)
2. Kit  comes with infineon chip controller  (controller is also programmable eg. low voltage cut off and max amps)

3. Throttle supplied with kit:
thumb or twist type ( can come with leds for battery voltage monitoring depends on customer choice). Choice of throttles shown below.

4. Kit comes with brake handles ( with cut off switches which can either be used for regen braking or for cutting off controller power when brakes are applied just as a safety feature)

How to Instal metal gears:
Remove circlip shown below, the whole gear assembly slips off in direction of red arrow, each gear is then removed from the gear assembly by removing a circlip on each gear..

Just a note that the development and knowledge on this motor over the years has been influenced by a large number of people. They all really deserve credit for the work they have put in to it, heres a few:
bmc china of course
eezybikes china
Knoxie uk a huge amount of work into getting the bmc 500watt motor (puma) "out there"
team hybrid uk/evtech usa: instrumental in getting bmc to make the 500watt (puma) bmc motor
steve (ozgenius) australia ( for abusing motors and finding out what it takes to break them!)
heaps of people on endless sphere forum toooooooooooooo many to mention

A bit more info on bmc brushless geared motors on the market and brief history here

 

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Copyright 1998-2009 by Brett White on all images/text/information and graphical materials on this website.