5.7 Wiring

Wiring Diagram

I can't take credit for the wiring diagram.  It was drawn by a friend and fellow ePure owner.  But I did sign off on it, so blame me if you find an error. 

A wiring diagram is a basic necessity that should have been provided by Electric Motion.

Note that I sometimes refer to ground” in various parts of this website.  Understand that to mean the negative side of the battery which is also sometimes called “return.” 

Nothing in the bike's circuitry is electrically connected to the chassis.

EM 5.7 schematic.pdf


All electrical connectors for switchgear wiring are AMP Superseal 1.5 series.  It's nice these connectors have numbered pins as that makes documenting the wiring more straightforward.  Striped wires are described using the main wire color first, followed by the stripe color after the slash.  These connectors are quite large.  Smaller ones would have been more in keeping with the scale of the bike.

I had planned to make a custom wiring harness for the 5.7 over the winter.  That would be good for a slight weight and complexity reduction.  Kelly sells the 14-pin controller connector for $9 – which is quite reasonable – but the shipping from China is an additional $21.  And, unfortunately, they come with a length of wire already attached.  I'd prefer not to have to desolder their wires and just start with a brand-new connector.

Eventually, I was able to determine the circular connector is called a GX20 “aviation” style.  (But if that's what they are actually using on Chinese airplanes, I don't want to fly in any!)  I purchased several via AliExpress very inexpensively.  Unfortunately, they do not fit the Kelly controller.  The diameter was off by about 1mm, and they won't screw together.  I don't know if this is just a tolerance issue, or if Kelly intended to be the only source for the mating connectors.

Lanyard Kill Switch

The controller has no “kill” function.  The lanyard switch goes to the controller's regeneration input.  This makes sense as the quickest way to stop the motor is not just to allow it to coast down (like an ICE), but rather to actively decelerate it.

Magura Throttle

The throttle is a standard Magura electric twist grip (type 317) made in Germany.  Magura sells it in three variations, depending on wire length and connector type.

The throttle potentiometer is nominally 5k ohms.  Mine measures 5.35k ohms between the blue and black wires.  The brown wire is connected to the wiper.

The twistgrip exhibits a very quick action, providing only 72 degrees of rotation by my measurement (Magura claims 75 degrees).  In comparison, the “fast” throttle tube on my OSSA turns about 80 degrees.  (I expect this varies somewhat with different carbs.)  I did not have any “slow” throttle tubes to measure but expect they turn at least 90 degrees, perhaps 100.

The throttle potentiometer is connected between ground and +5VDC provided by the motor controller.  The wiper then exhibits a variable voltage in proportion to throttle position, increasing (linearly, I expect) as the throttle is opened.

Deadband Adjustment

I'm defining “deadband” as the amount the throttle must be mechanically rotated before it causes any movement of the motor.  Think of it as adjusting the throttle cable free-play on an internal combustion engine.  (Additionally, the controller itself will have a setting for the voltage at which the throttle begins to take effect.  Kelly calls this parameter the effective starting voltage.

There are a pair of gears in the throttle handle that require an alignment for proper operation.  This limits the change to an integer number of gear teeth.  Unless you have disassembled the throttle handle, realignment of the gears should not be necessary.  However, what may be desirable is a small change in the orientation of the potentiometer.  Electric Motion made a video on this procedure.  A screen capture of the most relevant part is shown below.  Basically, you need to loosen a locking screw that bears against the potentiometer so that it is free to rotate.  Rotation is then accomplished by carefully prying against the wires.

A few degrees of rotation can make a big difference.  Personally, I like having almost zero free play.  I expect Magura/EM sets the throttle up with excessive free-play as a safety feature. 

5 k ohm throttle potentiometer

Credit: EM,  Magura deadband adjustment

Map Box & Map Switch

The map box and map switch modify (reduce) the throttle voltage before sending it on to the controller.  In Novice mode, the maximum voltage is 0.987 V.  In Trek, it's 1.363 V.  Wet Trial is 2.103 V and Dry Trial is 2.662 V.  

Note: the controller's configuration software is factory set for 60% of 5 volts, which indicates a maximum expected input of 3.0 volts.

OE Electronic Clutch

The 5.7's standard “electronic clutch” is nothing more than a normally-open switch wired in parallel with the lanyard magnetic kill switch.  When the lever is pulled-in, it's just like ripping the lanyard magnet off – very abrupt!

Brad Baumert, formerly of Ryan Young Products (the first US importer for EM) described this type of electronic clutch control to me as an “Oh Shit!” switch.  I find this moniker quite apt.  You really only want to use it in an emergency situation.

EM seems to have thought it could be used in the same manner as a “clutch dump” i.e., to get a burst of power.  But it can't.  At least I can't use it that way.  For one thing, there is no energy stored in a flywheel.  For another, the release of a mechanical clutch lever is not an instant on/off thing – there is a period of slip (however brief) which makes for a controlled launch instead of a lurch.

I'm somewhat curious about what's inside the AJP clutch master cylinder, but the reservoir lid won't come off without a fight.  The whole thing may be potted in silicone sealer.  It also takes a surprisingly large finger effort to pull in the lever.  I no longer care.

If you are used to having a mechanical clutch, this electronic clutch lever exhibits some pretty weird behavior.  I found it unnatural and basically unrideable.  Fortunately, it was extremely easy to make it into something that was rideable (albeit still imperfect).  See the Simple Clutch Mod section for more information.