Experienced builders have preferences for every part of their hot rod ebike, but…if you are new and you just want some advice on how to get started with components that work well enough, and are still reasonably affordable and available?…then this article is for you.
You don’t have to look long before you see that many common ebike controllers have a LOT of wires and connectors. I mention the controller first, because the controller is like the sun…around which the throttle, battery, and motor will orbit. The more powerful 18-FET controllers that are sometimes used for 2600W-8000W hot rods are often sourced from a Chinese E-moped/E-motorcycle supplier. These have added features, like a 3-way power switch, cruise control, reverse, regen-braking, speedometer, and others.
For those ebikers just starting out, this article will cover connectors for the three phase wires for the motor, the hall-sensors, the throttle…plus, the ignition wire (either hot-wired, or attached to an on/off switch). These should get you rolling, and then you can sort the other wires over time by contacting the vendor that you purchased the controller from.
We ALWAYS recommend that you get the throttle, controller, and motor from the same vendor (plus, buy a spare throttle!). If you try to mix-and-match parts? the color-codes on the wires might not match, the connectors won’t match, and…even after you swap-in matched connectors in the vital locations, the vendors will not help you trouble-shoot why some part isn’t working right.
You ‘can’ get a battery from the same vendor as the rest of the kit, but…it’s not a big issue to get a battery from a different supplier, as I layout in this article about making the battery-to-controller connection…
Motor Phase Wire Connectors
These are typically the easiest to identify (from the rats nest of wires). Most hubmotors will have either a single cable (with a bundle of wires of different sizes inside it)…OR, you can see the individual wires coming out of the hollow portion of the axle. These motors are three-phase, but…instead of having six phase wires exit the axle (which would restrict how thick each wire could be), there are only three phase wires coming out of the motor case. Sounds odd, but it’s true.
It’s because electricity will only flow through a complete circuit (both an inlet and an outlet). Therefore, one each of the two legs of each of the three coil-group wire-ends are connected together inside the hubmotor (either in a Delta or Wye configuration…confused yet?). As a result, you can rotate power through three electromagnetic coil-groups (six coil-group legs), and only three of the six coil group wire-ends will need to exit the motor case.
This is important to understand, so you will have confidence in what I say next. You can plug-in your controller to the three fat motor phase wires in any combination that you want (usually Blue, Green, Yellow…in alphabetical order), and it will not hurt anything. A “wrong” combination might spin backwards, or it might run a little hot fairly soon with no load on it, but…you can swap them around without frying anything.
I have bought motors that came from the vendor with Anderson connectors for the phases, and also the common ring connectors. There is nothing wrong with those, but I prefer using bullet connectors, and I like to attach the male bullets on the motor side (female on the controller side).
I also like to make the motor phase wires that are outside of the axle long enough that the connectors are inside the battery compartment (or bag). This is for waterproofing if I’m caught in an unexpected rain. However, many builders like to keep the phase wire connectors right near the motor, to make it easier to change a flat tire.
Using male bullets on the motor phase wires may be a holdover from back when we had to run the connectors through the axle-nut, because the phase wires on smaller motors come through a hollow axle, and…since the axles are pretty small, the axle-nut is also pretty small. Male bullets are smaller in diameter compared to their matching female sockets.
All the popular hot rod hubmotors now have the wire cable coming out of the motor case at a location inside the frame drop-outs (instead of at the axle-tip). This not only allows the axle to be stronger, it makes it much easier to upgrade the phase wires to something fatter than what the factory installed (since they don’t have to pass through the narrow axle-nut hole).
I like my three motor phase wires to be fatter than the stock wires (at least the sections that are outside the motor shell), and I want the connectors to be bigger too. That way, if the motor is running fairly warm from high amps, the external wires and connectors will not be the limiting factor. Also, since I am starting to see temp sensors installed inside the motor cases more and more these days, that means if the wires and connectors are running cooler than the motor, then the motor is the only part you need to monitor.
XT90’s are my connector of choice for the battery-to-controller up to about 3000W (with an anti-spark female connector on the battery side). As a result, I have a whole bag of male and female XT90 connectors. This way, any batteries and controllers I buy in the future will all have the same connector, and I can swap them around as needed (I buy pigtailed connectors, and use a simple butt-splice). Also, this way I can easily swap-in my back-up diagnostic controller to trouble-shoot problems.
Regardless of the style of bullet connector I might have spec’d if given a choice…I was in a tight spot once (in a hurry, couldn’t wait for shipping), and I cut open a couple of XT90 connectors with a thin abrasive cut-off disc on my Dremel, to harvest the 4.5mm male and female bullets out of them. They worked well, and since they are rated for 90A temporary peak, I was certain they’d work fine for motor phase wires (at the modest 50A that I use), and they have. (de-rate every spec in the ads for Chinese products…for example, the 90A pins in the XT-90 work great for an actual occasional 50A)
If you choose a certain size of bullet connector for most of your hot rod ebikes, a cheap place to buy a whole bag of them is Hobby King. On their home page, go down the left column on their home-page to “Hardware and Accessories”, then got to “Wires and Connectors“. That will get you to the general area where you can click on the specific types and models that you want. When it comes to bare male and female bullets (for motor phase wire connections) they currently carry 4mm, then 5.5mm , and also 6mm (Oct 2016).
The AS150 (Anti-Spark, 150A) connectors for a battery use 7mm bullets. The voltage of your system doesn’t matter, it is the current flow in amps that determines how large the pins need to be, so they won’t overheat. If the pins are fatter than the wire, then the connectors will always run cooler than the wires. The XT150’s use a 6mm bullet, but they are a little different than the bare 6mm bullets (which are from a different manufacturer).
[Motor phase wires are energized 2/3rds of the amount of time that the battery connector is energized. Choose a connector style that you like, but…the battery connection should be slightly larger than the motor phase wire connectors…also…motor phase wires can be fairly long, but the two red/black battery-to-controller wires should be short and fat, due to inductance]
4mm bullets are factory-rated for up to 60A peaks, and are acceptable for systems as low as 48V X 25A = 1200W, however…I personally use 4.5mm bullets for all my systems up to 60V X 50A = 3000W simply to have a common interface.
Be aware, I know someone who ran only 50A through common connectors, and after a few minutes, the solder melted. However, he was running 50A continuously (ES member livesforphysics/Luke). If you make the wires and connectors outside of the motor thicker than whats inside, then applying too much continuous load would melt the solder inside the motor first, but…you can avoid that by adding a temp sensor inside, and also sizing the motor to properly fit the loads you plan to use.
For continuous amps of 50A or more (typically using 10-ga wire or fatter), you should use a dry crimp connector, because high heat can melt your solder. Occasional temporary peaks of 50A will not damage a 4.5mm soldered bullet connection.
If I had it to do all over again, I’d just buy a big bag of 6mm pins and sockets for the motor phases. They are only 50% fatter than the tiny 4mm bullets, but their added length and mass means they can carry double the current. They can seat wire diameters up to 10ga and and also the very fat 8ga.
I would have preferred to buy a soldering box, but I built one from free scrap that has the exact features I want. I need portability because sometimes I work a night shift, where my only job is to respond to alarms, and stay awake…so the lunch room smells like solder when I go home. When it is folded out, it holds the HOT soldering iron with the tip suspended in the air as a “third hand”. This makes it fast and easy to “tin” the tips of wires.
This is where one of my hands holds the wire tip onto the soldering iron, and the other hand is free to add some solder. Put a dab of solder on the fat tip of the 100W soldering iron (to help it transfer heat easily), set the bare copper wire tip onto the blob of solder, and feed some more solder down into the strands. If you have a powerful 100W soldering iron, this goes very fast. In this way, the wire tip and the connector socket already have solder on them when I join them. When I make the final connection, I just hold them together and heat the joint up.
The wooden edge of my soldering box has holes drilled into it of various diameters. This allows me to insert a male or female connector (with the back-end socket facing up) to hold the connector as another “third hand” while I solder the wire tip into it. (*sips beer and stares off into space…”Why won’t anyone lend me a hand?”)
I use a refillable butane-flame barbecue lighter for portability. If I was on an assembly line, I’d use an electric heat gun. The unit shown has a flexible neck, and can throw a flame directly downwards, or in any direction.
Hall Sensor Connectors
Hall sensors are useful, especially if you are stopped on a steep uphill, and you need to get started from a complete stop. The alternative is to use a sensorless controller. I have a small sensorless controller as a back-up, and also as a trouble-shooting tool.
However, a sensorless controller will sometimes cause the motor to jiggle back and forth for a moment, until you can get the wheel moving forward. With properly-working hall sensors, you can be at a complete stop, and just touching the throttle will instantly start moving the bike forward.
My personal preference is to start out using the hand throttle (which runs off of the Halls), and once running, I start to pedal, which actuates the Pedal Assist Sensor (PAS). I consider Hall sensors to be a safety feature if you ride your ebike in traffic…because you should not rely on something that occasionally hesitates just when you need it most.
There are three Hall sensors, and each has three legs, for a total of nine. However, two of the legs on each Hall are for the 5V positive and negative power. As a result, those six legs are bundled into two wires coming out of the axle, and those two wires should always be colored red and black, for the positive and negative. The three remaining legs (one each for the Halls) are for the on/off signal to the controller. The grand total is…five thin Hall sensor wires coming out of the motor case.
They are VERY thin. They can be as thin as 36-ga, but I prefer a slightly fatter 24-ga, because it is easier to manipulate when soldering or crimping them. Since there are five, they are often sold with a common connector that has six pins. It is a large white square housing, and…although these annoyed me when I first encountered them, I now like them. I’d like to take a minute to describe their benefits, so you can see if they would work for you too.
Common wire insulation is Poly-Vinyl-Chloride (PVC), but for high performance it makes me throw up in my mouth a little. Silicone insulation is very flexible, soft, and high temp (Like Hobby King wire) but…it’s also very fat, like my dog. For any wire that needs to go through a tight spot to get from the inside of a motor to the outside, I pay a little more to get Teflon/PTFE insulation. Very high temp, and it is surprisingly thin…that way, the overall wire thickness can be mostly copper instead of insulation.
“Molex” style connectors are made in variety of sizes and configurations. We only need to be concerned with a 5V signal at extremely low amps. However, the smaller the connector, the harder it is to manipulate the individual pins and sockets.
“The problem” is that even when two manufacturers use the same connector-pair, they often do not set the pins in a pattern that are the same. Once I learned the trick about how to remove the pins and sockets from these housings (and then to re-insert, seen below), I can now move them around inside the housing so that both male and female connectors match the wire colors on both sides…no matter who I bought the motor and controller from.
The common Molex Hall-sensor connector is a white plastic square housing with six pins (two rows of three). Sometimes the sixth pin-position is empty, and other times it has a wire that is used for a temp sensor or possibly a speedometer signal. The housings also have a latch so they will not come apart by accident in the middle of a ride. The common colors are red and black for 5V positive and negative…plus Blue, Green, and Yellow (BGY) for the three signal wires (they should be in alphabetical order, because I have OCD, which should really be spelled CDO).
You must never plug in the red and black wires backwards (red to black, black to red). Also, you must never plug the red or black wires into the BGY wires. However, when you are trying to find a combination that runs smoothly, the BGY wires can be swapped around between each other without any damage to the Hall sensors.
This brings up the question, when you have a motor, and you don’t know how the BGY wires are configured inside, how do you test them? Imagine that there is a bicycle in front of you, the kickstand is out, and it is leaning to the left. You are standing on the right side and looking at the rear hubmotor.
From this perspective, the rotor (motor case rim) spins clockwise in forward, and there are three Hall sensors. One is in a trailing position, one is in the middle, and one is in a leading position. On a motor from a certain vendor, perhaps the middle Hall sensor uses a yellow wire for the signal, but…what if a controller you want to use is from a manufacturer who uses a green wire for the middle Hall signal?
Between the three fat phase wires to the motor, and the three skinny BGY wires to the halls, you have to find a combination that spins the tire in the forward direction, and also has a low “no load” amp-draw (you DO have a watt-meter between the battery and controller, right?). If…the motor is using the correct phase and Hall wire configuration between the motor and controller, it will spin in the forward direction, it will run cool and smooth, and the amp-draw will be low (doesn’t get warm).
First, spin up the motor with a sensorless controller, to verify the motor phases are working fine. Make up five thin jumper wires to connect the Hall sensor pins and sockets from the mystery controller to the mystery motor (seen in the pic below). Now, you can begin swapping the wires around to see what works. On the list below, electricity flows from the controller to the motor, so the first letter is the controller wire color, and the second letter is the motor wire color…
B=Blue, G=Green, Y=Yellow…BGY
Controller –> / –> Motor
B/B_G/G_Y/Y (start with all the colors matching)
B/B_G/Y_Y/G (swap the Green and Yellow wire positions)
You can see here that there are only six possible motor phase combinations (when using three colors of wire), but…when we factor-in that there are six possible Hall sensor combinations for EACH of the six motor phase combinations, then there are 6 X 6 = 36 total possible combinations, in order to find the right one.
Remember, you only swap around the BGY wires, the red and black on both sides should be the 5V positive and the ground. Connect red to red, and black to black. You MUST identify the Red/Black positive and negative wires first!
If you are using a sensorless controller, there are only two phase wire combinations. Start with the three motor phase wire colors being matched, then also try it after you swap the green and yellow wires. One of these two combinations will provide forward rotation, and the other combination will provide reverse. Once you find the combination that provides forward, re-mark the wires so the colors on both sides of the connectors match. I mark the motor phase pins and sockets with a short piece of colored heat shrink.
Here is a great 3-minute video where Micah Toll (from ebikeschool.com) shows the Hall sensor connectors, and how to insert or remove the pins.
The simplest ebike throttles have three pins in the connector. The controller sends a 5V power supply to the hand-throttle (positive), along with a second wire that is the ground (negative).That leaves the third wire as a signal wire that sends a signal back to the controller to tell it what you want. The signal wire can provide anything between 1V up to 4-ish volts.
Just like before (with the hall wires), the 5V positive and negative should be red and black, and they can be very thin wires. The third signal wire can be any color you want, as long as the connectors match. Using a thicker wire won’t hurt, but…it also won’t help. I use 24-ga with thin and high-temp teflon insulation, simply because I have a large roll of it for motor hall connections.
In the pic above, the Futaba connectors at the far left (found on RC models) use wires that are black/red/white (good), but…the JR connectors use green/brown/yellow (clearly they hate America, freedom, and puppies). Notice the Airtronics connector above the JR connector has the black (ground) wire in the center, but the Futaba has the black (ground) wire on the edge.
RC connectors are very small (which seems handy), but…the pins are very difficult to crimp the bare ones onto wire, and they are difficult to insert or remove (for swapping-around their position). Some RC connectors have a latch, so they don’t pull apart by accident…while others don’t have a latch, and hold together by friction alone.
[Be aware, throttles from E-scooters and E-motorcycles are sometimes used on hot rod ebike kits, and they might include a cruise control wire, a regenerative braking wire, a 3-way power limiting wire, and sometimes an on/off switch wire…sometimes even a headlight switch]
Ignition Wire Connector
The simplest controllers don’t have an on/off switch, and they don’t provide an ignition wire to connect to a switch. When you plug the battery into the controller, it is powered up. I suppose doing that saves having a 50-cent switch, but forgetting to unplug when you’re done riding can drain your battery down to a damaged level, and having no “anti-spark” circuit on the power-up can wear out any on/off switch you add. But hey! They saved you 50 cents, right?
However, the 12-FET and 18-FET sized controllers in this “hot rod” category typically have an ignition wire. This means that you will NEED to wire it up correctly, or the system will not turn on, or run at all. IF…you have an ignition wire, make certain to find out from the vendor that you bought it from how to wire it up. It’s also just a 5V signal at very low amps, so a wide variety of readily available switches will work in this application.
I highly recommend that you use a switch instead of hot-wiring this to be “on” all the time (like in the pic below). If you hot-wire it, you would have to unplug the battery to turn the system off, and plug-in the battery to turn it on.
There is no standard way to have an ignition wire, and plugging any provided IGN wire the wrong way can fry stuff. I have had good luck with Kinaye components, so here’s an example from them. He sells his controllers with a skinny red and yellow wire that have matching male/female connectors. If you want the controller shorted to “ON” when the battery is plugged in, you plug those two wires into each other. If you want an on/off switch, or possibly a key switch, the two wires from the key switch get connected to those two red/yellow wires. You can request pigtail connectors for the IGN, or you can clip the shorting connectors and solder the switch onto the yellow and red wire ends.
In short, get very clear instructions from whoever you buy the controller from, as to how to wire it up. A picture on a website would be even better, to avoid a mis-communication. Some provide a thin red wire stub, which hopefully is labeled. It “might” be intended to wire up to the fat red battery positive, or to pass through a 2-wire switch, and then to the fat red battery positive. If it has an IGN wire, it will not power-up until the IGN wire is properly sorted.
If (for some reason), the motor power accidentally comes on without you applying the throttle (or you turned it on, but now it won’t turn off), it is good to have a large “OFF” button that can be pushed-in to cut the power (a kill switch). However, in the situation where that actually happens, a riders’ first instinct is usually to apply the brakes.
An E-brake is just a regular bicycle brake handle, but…it adds a tiny magnet attached to the moving part of the handle, and then the mounted part of the brake has a magnetically-sensing switch in it (usually a Reed switch). When you move the magnet away from the sensor (by pulling the brake handle) a 5V signal is then sent to the controller to cut the power to the motor. These only need two wires to their connector, because it is not variable. The signal is only on or off.
If your wires are not labeled, the E-brakes are usually easy to find. They are two small connectors, with each having two small wires running to them. They are typically identical. One kit I worked on had three very similar connectors that I thought looked like E-brakes. But…upon closer inspection, two of them had female connectors, and the third had a male connector. Once the vendor responded, they verified that on this particular model, the two tiny identical female connectors were the E-brakes. One for the front brake handle, and one for the rear brake handle.
The color of the wire is unimportant, they only have to make an on/off 5V signal. However, if they are accidentally shorted somehow, the controller thinks the brakes are on all the time, and the controller will not turn on.
Extenders, pigtails, and butt-splices
If you want to try to connect those tiny pins and sockets onto the ends of tiny wires, I wish you luck. It is very cheap and so much easier to buy an extender, and then cut it in half. That way you end up with a male and female connector set, and each has a few inches of wire already installed.
You can find extender cables on Google or ebay, just search “6-pin molex connector”, or for throttles a “3-pin Molex connector”. The extender for this article was purchased from allelectronics.com for $3 (not a typo, $3 for a male/female pigtail set). Hopefully they won’t change the link in the future, it’s for a “6 conductor connector”, under “connectors (multi pin)”. And also, here is their link to the 3-pin Molex for the throttle.
There are minor differences in Molex-style connectors from one vendor to the next, so once you try a sample and you’re happy with it, get a whole bag so they will always fit with each other. At worst, if you change your connector type in the future? you can sell the Molexes on endless-sphere, an ebike forum.
By using pigtails, you can easily swap a horrible type of connector to the kind that you like. Then, you only have to make a butt-splice to connect the wires from the controller to the motor.
For portability, I have some copper crimp sleeves in my kit. As seen below, you take two butt-ends of wire, slide on a section of heat-shrink insulation, intermesh the wire tips (Don’t stick them in side-by-side, intermesh all the tiny strands). Slide the metal sleeve over the joint, crimp it down as hard as you can, then slide the heat shrink insulation over the joint, and heat it up with a cigarette lighter.
If you bought the motor, controller, and throttle from the same vendor…they should all be “plug and play”. However…if you think you might mix-and-match a controller, throttle, and motor from separate vendors someday…you will have to decide on which connectors to use (if they are not the same).
There is no “best” connector for each of these jobs. I only hope that this article helps you get rolling, and that way you can be riding your ebike, until you get enough time to figure out what connectors you want to end up using down the road.
Ride safe, and have fun.
Written by Ron/spinningmagnets, September 2016