TQFreak's Dengfu E55 Build Thread

[TQFreak]

They connected it this way because it does not require the connector modification and the stock Bafang M620 power is not too big so they can use just some of the pins for battery. If you do not want to modify the connector you have to follow what they did and double check if the button for the BMS switch you are going to use has the same wiring. If the BMS you are going to use has different button wiring then you can not use this connector as is. The BMS they used for this bicycle shares positive battery terminal for the button I guess. I do not know if this is the same for my BMS or for the BMS you are going to use. I know the BMS I used has dedicated pins for the button on the PCB and I do not know if one pin is shared with the battery positive terminal, I just modified the connectors adding more connectors for the button.

The sock connector you have wired this way is capable only limited power because of the battery does not use all 3 pins on each terminal. If you are planning to use more power with different motor controller like Innotrace for instance or you are planning shunt mode the stock Bafang controller to have more power you need to use more pins for the battery to make it able to withstand the high amperage without overheating.

I use 3500W motor controller and battery capable 80A (with 80A BMS) so I use all the pins for the battery (3 for each terminal) because of high amperage. In order to connect button I modified the connector on the battery side and 3D printed an additional connector for the battery connector on the bicycle side and used pogo pins to make connections for the button when engaging the battery. I explained the details in this thread.

If you want to modify the connector like I did modifying the connector with soldered wires you already have might be difficult so you might need to purchase new connector parts without wires for the battery if you are planning to connect the battery different way. This is Reention Rino battery and connectors, but I do not remember the part number, you need to do research.

 

[jonnyfive]

They connected it this way because it does not require the connector modification and the stock Bafang M620 power is not too big so they can use just some of the pins for battery. If you do not want to modify the connector you have to follow what they did and double check if the button for the BMS you are going to use has the same wiring. If not you can not use this connector as is.

The connector wired this way is capable only limited power because of the battery does not use all 3 pins on each terminal. If you are planning to use more power with different motor controller like Innotrace for instance or you are planning shunt mode the stock Bafang controller you need to use more pins for the battery to be able to withstand the amperage.

I use 3500W controller and battery capable 80A so I use all the pins for the battery (3 for each terminal) because of high amperage. In order to connect button I modified the connector on the battery side and 3D printed an additional connector for the battery connector on the bicycle side and used pogo pins to make connections for the button when engage the battery. I explained the details in this thread.

Modifying the connector with soldered wires you already have might be difficult so you might need to purchase new connector parts for the battery if you are planning to connect the battery different way. This is Reention Rino battery and connectors, but I do not remember the part number, you need to do research.

I see, I understand now. Thank you! I only plan on using the M620 motor.

Since the switch is on+1, and then +2 along with the charge port and battery power positive wires, it it correct to think that I would only wire one of positive wire from the battery to +1 then? And negative wires from the BMS only to "+"3 and -5?

Also, I thought it wasn't possible/safe to use a simple switch on a high voltage circuit like this?

 

[TQFreak]

The voltage this battery uses is not dangerous for human. But if the wires will be shorted the amperage is high and it can cause fire. I do not know which BMS you are planning to use, but different BMS might have different connections. You have to follow what the BMS manufacturer shows in their wiring diagram. If the button does not share the positive pin with battery according to the BMS wiring diagram (like the BMS I used for instance), then you need to modify the connector the way it has dedicated pins for the button.

I believe you can purchase the stock BMS they use for this battery so you do not need to modify the connector. But I am not familiar with with how that BMS should be connected, you need to do research.

On the BMS I used the charge port is connected parallel to the battery terminals and the button has dedicated pins. I used just a low amperage fuse for the charge wires close to the place where they merge to the battery wires to make it a bit safer. The battery wires have a high amperage fuse I placed inside the battery case.

Regardless of what you see on that connector there are also connections inside the battery going on so the wiring you see might not tell you much how to connect the battery. You need to find the wiring diagram for the BMS you are planning to use and start figuring out from there.

So the answer is I do not know how to connect it for the BMS you are planning to use. I know how to connect it to the BMS I used - paralleled battery terminals and charge (I recommend to use 2 pins for each terminal) and 2 dedicated pins for the button (so totally you need 6 pins out of 6 this connector has). The connector you have will not work as is without modification for the BMS I used.

 

[jonnyfive]

The voltage this battery uses is not dangerous for human. But if the wires will be shorted the amperage is high and it can cause fire. I do not know which BMS you are planning to use, but different BMS might have different connections. You have to follow what the BMS manufacturer shows in their wiring diagram. If the button does not share the positive pin with battery according to the BMS wiring diagram (like the BMS I used for instance), then you need to modify the connector the way it has dedicated pins for the button.

I believe you can purchase the stock BMS they use for this battery so you do not need to modify the connector. But I am not familiar with with how that BMS should be connected, you need to do research.

On the BMS I used the charge port is connected parallel to the battery terminals and the button has dedicated pins. I used just a low amperage fuse for the charge wires close to the place where they merge to the battery wires to make it a bit safer. The battery wires have a high amperage fuse I placed inside the battery case.

Regardless of what you see on that connector there are also connections inside the battery going on so the wiring you see might not tell you much how to connect the battery. You need to find the wiring diagram for the BMS you are planning to use and start figuring out from there.

So the answer is I do not know how to connect it for the BMS you are planning to use. I know how to connect it to the BMS I used - paralleled battery terminals and charge (you can use 1 pin for each terminal) and 2 dedicated pins for the button (so totally you need at least 4 pins out of 6 this connector has). The connector you have will not work as is without modification for the BMS I used.

I was referencing the frame switch not the BMS switch. The way it is wired in my picture, it will be seeing the full battery voltage. I thought that was incorrect and a relay was needed.

I don't think my BMS choice has much of anything to do with how the battery +/- is connected into the terminals in my picture? That was really my main question that I'm still trying to figoure out, and the only thing that matters is how they've decided to wire the terminals I showed above? The BMS wiring diagram sheds no light on this. In fact I likely won't even use a BMS with a switch, as it's redundant, so I'm not really worried about that.

 

[TQFreak]

That frame switch controls BMS (this is BMS switch, it commands the BMS to turn the voltage of the battery ON and OFF). You do not connect this switch to the high amperage battery leads!

There are BMSs do not have switch - in this case you do not use this frame switch. That frame switch is for BMS control only if the BMS has such function!

If you will contend this switch in line to the high amperage high voltage battery leads you will set you bike on fire! DO NOT DO THIS!

 

[jonnyfive]

That frame switch controls BMS (this is BMS switch, it commands the BMS to turn the voltage of the battery ON and OFF). You do not connect this switch to the high amperage battery leads!

There are BMSs do not have switch - in this case you do not use this frame switch. That frame switch is for BMS control only if the BMS has such function!

That makes sense! But the wiring in my pictures still shows the frame switch sharing the same terminal as the motor power. How is that not 52V? The way it's wired up is what I can't understand.

 

[TQFreak]

If it shares 52V it is likely sends it to the MOSFET or relay on the BMS PCB or something (depending on the BMS logic) but it does not switch high current directly. The other end of the switch is connected to a dedicated pin on the BMS, but this switch is not part of the high current battery circuit, it controls that circuit through the BMS logic, it just takes voltage from the battery to control the logic on the BMS (MOSFET or other transistor or relay).

 

[jonnyfive]

If it shares 52V it is likely sends it to the MOSFET or relay on the BMS PCB or something (depending on the BMS logic) but it does not switch high current directly. The other end of the switch is connected to a dedicated pin on the BMS, but this switch is not part of the high current battery circuit, it controls that circuit through the BMS logic, it just takes voltage from the battery to control the logic on the BMS (MOSFET or other transistor or relay).

I see. Did they just not care that the terminal block is marked positive for pins 1-3 and negative for pins 4-6? It's throwing me off for instance that the charge port is wired to +2 and +3.

I also re-read your earlier comment and I think I'm starting to grasp the concept of why they wired it this way. Every BMS switch I've seen is not connected to battery power and is totally independent, so I guess the way they have it wired is for a BMS that does require the battery power wired into the switch. So like you said, I would probably need to rewire this connector, but in the end it depends on my BMS (I have two Daly BMS both with switch and without that I was going to make use of, and the switch wires are independent of the battery wires).

 

[TQFreak]

Yes they did not care about the markings. Please also be aware the way they connected it is now standard for this frame which means if you will modify the connector you will not be able to use "standard" battery for this frame you can purchase somewhere.

This is how I connected my BMS. If your BMS has same wiring you can use just 4 pins from that connector as you can see (as long as you do not overcome the default amperage). The Switch on the picture is the frame switch. I used all 6 pins just for the battery leads and the charger (3 for each terminal) so I have to make an additional connector with pogo pins for the switch circuit.

 

[jonnyfive]

You bring up a good point about any standard future battery not working in this bike if I modify those pins. It seems smarter to not modify it in case someone tries to replace the battery one day. It sounds like they use a "Seiko IC BMS" in this battery, but after hours of searching that's as close as I've gotten. The listings I've found that mention that model say nothing about a switch. I can't find any wiring diagrams for this make of BMS either to verify I would getting the correct one.

 

[jonnyfive]

Anyone know what material the screws/bolts included in the E55 bike kit are? Are they stainless steel? Specifically the ones that attach various parts to the frame.

 

[TQFreak]

The battery is attached with alloy steel screws (they are magnetic) with some kind of treatment. I ride mostly in the rain and they do not rust. Frame parts are fastened with anodized aluminum fasteners (you have to use treat locker with treat locker activator (because of the aluminum is anodized and treat locker will not be cured on anodized aluminum) on some of them otherwise they will get loose). I also recommend to apply marks on some fasteners (mostly on the rear triangle fasteners) to check sometimes if they starting to get loose.

 

[jonnyfive]

The battery is attached with alloy steel screws (they are magnetic) with some kind of treatment. I ride mostly in the rain and they do not rust. Frame part are fastened with anodized aluminum.

Thanks. I'll definitely be replacing them then. The issue is not rust from rain or water (although it will accelerate the corrosion), it is galvanic corrosion due to contact with the carbon fiber. It is inevitable over time.

 

[TQFreak]

Well, my fasteners are still fine and I ride mostly in the rain all year round (this is my rain commuter bicycle) and I never wash my bicycle also.

 

[jonnyfive]

Well, my fasteners are still fine and I ride mostly in the rain all year round (this is my rain commuter bicycle) and I never wash my bicycle also.

I think rainwater is very mildly conductive, so it probably takes a much longer time than in other applications. Seems like on the timeframe of years for most bicyclists. For a few dollars of fasteners it's probably worthwhile to replace with a suitable alternative. Not really a big deal either way. I personally live by the beach, so the salt in the air accelerates corrosion in everything. Marine grease on the stock fasteners probably works alright too.

 

[cbinvb]

Absolutely tremendous work TQ. I've been bouncing around to each of your threads and I'm just blown away at the depth of your projects for this hobby. Do you happen to be an EE?
Do you plan to manufacture any of the m620 controllers you developed?

 

[TQFreak]

Absolutely tremendous work TQ. I've been bouncing around to each of your threads and I'm just blown away at the depth of your projects for this hobby. Do you happen to be an EE?
Do you plan to manufacture any of the m620 controllers you developed?

I have no such plans but it looks like there are other guys assemble it. Maybe there is someone who wants to produce them in quantity, anyone can make it.

I am currently installing that new motor controller on this bicycle by the way, you can find some info here

VESC based INNOTRACE motor controller for Bafang M620 CANbus

The archive with the current versions of the motor controller files (KiCAD version 9.0.8), Gerber files, CAD files and firmware files can be downloaded here (updated on 2026-03-26). https://drive.google.com/file/d/1hCO7RL1AwwIHGNZ7YgvKHUjH4vSG7JOC/view?usp=sharing There are two PCBs in two...

endless-sphere.com

 

[Dado]

I have no such plans but it looks like there are other guys assemble it. Maybe there is someone who wants to produce them in quantity, anyone can make it.

I am currently installing that new motor controller on this bicycle by the way, you can find some info here

VESC based INNOTRACE motor controller for Bafang M620 CANbus

The archive with the current versions of the motor controller files (KiCAD version 9.0.8), Gerber files, CAD files and firmware files can be downloaded here (updated on 2026-03-26). https://drive.google.com/file/d/1hCO7RL1AwwIHGNZ7YgvKHUjH4vSG7JOC/view?usp=sharing There are two PCBs in two...

endless-sphere.com

TQ and what is your motivation to give it for free to someone who wants to produce it in quantity?

 

[TQFreak]

TQ and what is your motivation to give it for free to someone who wants to produce it in quantity?

The more people have it the more chances the VESC firmware will be getting better. The more chances someone will design other aftermarket controllers for other cool motors. You can make these controllers making them more popular and you will make some money in exchange.

 

[cbinvb]

I have no such plans but it looks like there are other guys assemble it. Maybe there is someone who wants to produce them in quantity, anyone can make it.

I am currently installing that new motor controller on this bicycle by the way, you can find some info here

VESC based INNOTRACE motor controller for Bafang M620 CANbus

The archive with the current versions of the motor controller files (KiCAD version 9.0.8), Gerber files, CAD files and firmware files can be downloaded here (updated on 2026-03-26). https://drive.google.com/file/d/1hCO7RL1AwwIHGNZ7YgvKHUjH4vSG7JOC/view?usp=sharing There are two PCBs in two...

endless-sphere.com

I have gone thru most of your threads and the info is a little difficult to parse at times with so many tabs open.
Are you saying this download "M620 UART VESC controller (Finished Release #3) (2026-03-19)" has all the information in it to construct the UART controller for the M620 and along with some programming guidance in your threads one could be back up and running as was possible with original X1 controller?

Are there any effective functional differences between your reverse engineered controller and the X1 aside from some of the board design improvements you've made and using VESC protocol?

Is there any reason to go with a the Can controller (for the canbus motor) over the Uart controller (for the uart motor)? I ask because I am ordering an m620 soon.

Thanks

 

[TQFreak]

I have gone thru most of your threads and the info is a little difficult to parse at times with so many tabs open.
Are you saying this download "M620 UART VESC controller (Finished Release #3) (2026-03-19)" has all the information in it to construct the UART controller for the M620 and along with some programming guidance in your threads one could be back up and running as was possible with original X1 controller?

Are there any effective functional differences between your reverse engineered controller and the X1 aside from some of the board design improvements you've made and using VESC protocol?

Is there any reason to go with a the Can controller (for the canbus motor) over the Uart controller (for the uart motor)? I ask because I am ordering an m620 soon.

Thanks

Benjamin Vedder is responsible for the firmware for the VESC for Bafang M620 UART controller. But I was not able to make that firmware works and I am not familiar with the VESC stuff. Benjamin Vedder does not share the instructions about how to make it works, but the VESC team guys claim it works and they tested it. If you want to make that controller you need to be familiar with VESC stuff or ask for help the VESC team.

The VESC for Bafang M620 CAN controller works no problem and the firmware works out of the box on that controller.

The VESC for Bafang M620 CAN is better than VESC for Bafang M620 UART because of it has more power, can work with higher voltage, it is more efficient, utilizes better cadence/torque sensor, has integrated Bluetooth and supports those nice looking Bafang CAN displays and technically should have support from Luna and Luna developers because of it utilizes the VESC firmware from Luna so any firmware updates Luna does for their controllers should work with the VESC for Bafang M620 CAN controller.

 

[bram.biesiekierski]

The more people have it the more chances the VESC firmware will be getting better. The more chances someone will design other aftermarket controllers for other cool motors. You can make these controllers making them more popular and you will make some money in exchange.

I consider myself pretty well versed with DIY, but feel totoally out of my depth with building PCBs and programming. I would be happy to pay for a ready to go controller kit. And i would expect alot of other people would probably feel the same.

I freakin love the m620. It is a beast, my only gripe with the platform is not enough power. Honestly if your kit was a ready to go plug n play unit, i would have 100% gone down that road instead of the CYC conversion.

 

[TQFreak]

I consider myself pretty well versed with DIY, but feel totoally out of my depth with building PCBs and programming. I would be happy to pay for a ready to go controller kit. And i would expect alot of other people would probably feel the same.

I freakin love the m620. It is a beast, my only gripe with the platform is not enough power. Honestly if your kit was a ready to go plug n play unit, i would have 100% gone down that road instead of the CYC conversion.

Maybe K1 wants to make them? He already started working on a controller, but since there are perfect open source controllers already why would put an effort to this. Maybe better to spent time designing VESC for Bafang M820 controller and finance this effort selling the VESC for Bafang M620 and M560 controllers

 

[cbinvb]

What have you done about the kinnerday hub?

 

[TQFreak]

What have you done about the kinnerday hub?

I replaced it by a 3x3 nine hub.

I also disassembled it and found the gears are worn out and fixing it would require machining new gears and other parts. Nothing else has been done

Kindernay maintenance.

I am afraid to destroy it doing so because if another drive-train will fail Kindernay is the only option I have (besides the oil leaks it just works). Also depending on the ratchet mechanism grease actually can make it stop working or make it works worst or can cause shearing and destroying the...

forums.electricbikereview.com

 

[RolandS]

@TQFreak Great post, I'm trying to decide which frame size of the E55 would fit best. How does it fit you? I am about 5'10 with a 31 inch inseam.

 

[TQFreak]

@TQFreak Great post, I'm trying to decide which frame size of the E55 would fit best. How does it fit you? I am about 5'10 with a 31 inch inseam.

5'6" 30"inseam I use medium size frame (medium is the smallest E55 size) and it fits OK.