Rebuilding a 6kW Ebike - need advice re. controller (Sevcon Dragon8)

I got a project Ebike (edit: it's a 200Kg electric motorcycle) a few months ago, ran poorly (range and torque), but it worked. Then I didn't have access to it for a couple of months, and the battery died (LiFePo4 80V, every cell reading <2V and most <1V).

I decided to redo most of the powertrain. New battery (24S1P 25AH LiFePo4 with room to expand up to 4P), new BMS (100amp 17-24S Ant BMS from ICGOGOGO on AliExpress. Not recommended), new DC-DC controller (2 Generic 150W modules from Amazon) and redoing most of the wiring (it was a crow's nest of patchwork repairs by some drunken monkeys with access to lots of electrical tape). Keeping the existing charger because it was almost new when I got the bike (<6months old)

So far it's been going well. I want to start testing the new setup, but I'm worried I'm too novice for this controller, a Sevcon Dragon8. From what I read, it's a pretty advanced one. With lots of bells and whistles and expensive diagnostic tools. I'm hesitant to hook it up, because if it's really above my league. Maybe I should just sell it off and buy something simpler that just does what I know I need (control my motor and make sure it doesn't catch on fire, basically).

So, am I over my head? On one hand, I know this controller works - I ran with with for a few months. On the other, this is my first EV project, and this controller has me anxious. Should I sell it and try to get a simpler one? Is there some place I can find documentation on it (all I can find is documentation for the Gen4, and they're not really compatible)?

How are you fitting 96* 25Ah LFP cells on a "bike"?

That's ~150lbs just for the bare cells!

I should've been clear, it's an electric motorcycle (not a bicycle).

My current 24S1P, with BMS and heat sinks weighs under 18kg (~40lb). So 72KG (158lb) battery for a 200KG (440lb) motorcycle (original rated weight with old battery) seems reasonable. No?. I could leave it at 2 or 3 packs. I don't really need the range.

Well it is true that if you do need to reprogram the controller, you likely need to find and pay a shop or freelancing professional to help.

I would think being willing to pay $3-600 per hour would help, to say those skills are thin on the ground is an extreme understatement.

But maybe it doesn't even need any changes in programming! And the level of help you can get from the members here might be enough...

Choosing another unit for that level of power is a challenge and likely won't be nearly as good - Nucular is on an 8+ month waitlist for example

Definitely wouldn't mind paying 3$ an hour to get some support with this thing (j/k. I know you meant 300). I believe I won't need to reprogram it since it worked fine before, I'm mostly worried about the pinout and diagnostics. BTW, if anyone has any leads on documentation/diagnostic tools, let me know. I don't mind pay a few hundred $ to get reasonable diagnostics on this device. It supports CANopen, but I never used it, so any advice on that would also be a appreciated.

Choosing another unit for that level of power is a challenge and likely won't be nearly as good - Nucular is on an 8+ month waitlist for example

Click to expand...

Jesus frock, 8+months. What about a some of the AliExpress devices like APT 96600, Sabvoton 96120 or this SiAECOSYS "brand" I've never seen, model 72180 (note my motor is rated to work at 72V, and having ridden on it at about 66% of its rated power, I think I wouldn't mind).

Right now, given what you said, I think I'm going to wire up my current controller. Any advice on low-tech diagnosis when things don't go as planned?

Even a 250W UK motor can run at 120V but more like what Grintech does is give a range of power levels, is a more desirable figure to state, because its not really a given stat for a given number in terms of watts for a motor, but a range. Even that 250W motor could be run at 1000V, theory speaking that is, question is could you find a controller.

SiAECOSYS is a good outfit by cheap Chinese standards, sales front end of the QS network, buy direct not through another layer.

but do not expect much English language assistance on tech details much less after sales support.

Maybe if you bought it with one of their reco matched motors as a kit, asked to pay extra for programming stuff??

APT gets a bad rap.

Default stance with Ali should be suspicion.

Thanks for the advice, I'll keep those in mind if I give up on getting my controller to work (haven't tried yet. I'll update when I will).

1st, your Sevcon is perfect and I wouldn’t change it if the replacement was free. You need to learn can-bus programming protocols because, that is what DIYers do: reading, learning, setting. Alternatively you could buy a very expansive handheld programming unit, or or plug an usb-canbus adapter and use the original software, or a bad copy of it OR, find someone to do it for you because he is in love with you or your money. DIYers don’t do that. Nothing beats knowing how to do it yourself, because you will be able to understand what you are doing and most of all, why it does need to be done.

Once you can program CAN-BUS, which is a very simple serial communication protocol that CAN be mastered in a day, a whole world of mechanic/electronic apparels can be addressed, read and set. Cars, motorcycles, boats, airplanes, industrial robots and machines... even my Meanwell PSU’s assembly charging station is CAN-BUS programmable. The more primitive your interface, the more different apparels can be accessed. A specific software won’t let you understand what what you are doing, only give you a set of short cut functions settings for your bike and nothing else.

Dragon 8 is a nice platform you would be glad to be running. Highest current density switched per package of any of the Sevcon/Borg options makes its burst power to mass ratio nice for LEVs.

Tuning it is not going to be very easy, but we've seen a few folks pull it off here with the Gen4 platform that is more complicated. That fact that its discouraging to you is a good sign that you could be aware of enough to pull it off with enough effort.

Remember the type of Dragon 8 you get can come in the Hall-sensor UVW style encoder, or the Sine/Cosine AB type, you are hosed if your motor encoder type doesn't match the controller type because its a hardware based difference.

Yep. Start with confidence: it is working, you can make it working better, and then you will be amazed at how better you achieved. And, if you make a mistake so it doesn’t work anymore, you will learn deeper because you will be forced to.

1st, your Sevcon is perfect and I wouldn’t change it if the replacement was free. You need to learn can-bus programming protocols because, that is what DIYers do: reading, learning, setting. Alternatively you could buy a very expansive handheld programming unit, or or plug an usb-canbus adapter and use the original software, or a bad copy of it OR, find someone to do it for you because he is in love with you or your money. DIYers don’t do that. Nothing beats knowing how to do it yourself, because you will be able to understand what you are doing and most of all, why it does need to be done.

Click to expand...

I don't mind learning CAN-BUS programming. Any resources you recommend to start with?

Remember the type of Dragon 8 you get can come in the Hall-sensor UVW style encoder, or the Sine/Cosine AB type, you are hosed if your motor encoder type doesn't match the controller type because its a hardware based difference.

Click to expand...

I'm fairly certain the controller matches the motor since the two worked well together for a couple of months.

First get yourself a can-bus adapter, and the manual for your controller. Familiarize yourself with can-bus com protocol here: https://www.csselectronics.com/pages/can-bus-simple-intro-tutorial

That's just it, I can't find the manual for the Dragon 8. After a week of Google and a couple of "contact us" forums, all I could find was a few (1, 2, 3, 4) pinout diagrams some people uploaded that seem to fit what I know about my device. All documentation I find is for the Gen 4, which is incompatible. I'd love to find serious documentation on the Dragon8. If anyone's got one, I'd love to buy a scan/copy from you.

Icgogo bms are great, highly recommended.

Tommm said:

Icgogo bms are great, highly recommended.

Click to expand...

I'm very disappointed with mine.

2x10AWG wires for 100amps soldered directly to the PCB (not a copper bar) and loose screws holding the metal plates onto the PCB gave me a feeling of cutting corners. It did work when I accidentally short circuit the battery through the BMS, but that's a low bar to clear. Generally I have very little confidence in it and will replace it when I finish this rebuild.

The fact that it ships with instructions telling you to download the wrong software, and you can only find out aboThut the error when I contacted their support. Then I got the real software, which is buggy. It doesn't always find the device, so I have to use another app to connect to it and the disconnect. The BT connection drops sometimes. The translations are poor AF (to be expected of Chinese translations, but doesn't make it not a pain-point). The worst part is that there's no sensible instructions on what any config means, so when the translation fails you, your stuck experimenting and hoping not to frock up too badly that it's irreversible.

neowizard said:

That's just it, I can't find the manual for the Dragon 8. After a week of Google and a couple of "contact us" forums, all I could find was a few (1, 2, 3, 4) pinout diagrams some people uploaded that seem to fit what I know about my device. All documentation I find is for the Gen 4, which is incompatible. I'd love to find serious documentation on the Dragon8. If anyone's got one, I'd love to buy a scan/copy from you.

Click to expand...

Ask for the manual directly from Sevcon. Contact the service dept. by email from their website.

Tommm said:

Icgogo bms are great, highly recommended.

Click to expand...

ICGOGOGO does not necessarily manufacture everything they sell?

but generally for an Ali seller they do get a lot of reco's.

Usually for the "olive leaf" dedicated balancers

but also the ANT version of smart BMS

https://www.aliexpress.com/item/32826820690.html

neowizard said:

Tommm said:

Icgogo bms are great, highly recommended.

Click to expand...

The worst part is that there's no sensible instructions on what any config means, so when the translation fails you, your stuck experimenting and hoping not to frock up too badly that it's irreversible.

Click to expand...

The explanation of the feature is communicated as you press the ok button. Not sure about the not connecting issue, you have to have location on for android. There are multiple apps that work with it, currently I use MaYi-bms, but last time I ordered from them they said they will have a new chip and a new app which will not be backward compatible.

MadRhino said:

neowizard said:

That's just it, I can't find the manual for the Dragon 8. After a week of Google and a couple of "contact us" forums, all I could find was a few (1, 2, 3, 4) pinout diagrams some people uploaded that seem to fit what I know about my device. All documentation I find is for the Gen 4, which is incompatible. I'd love to find serious documentation on the Dragon8. If anyone's got one, I'd love to buy a scan/copy from you.

Click to expand...

Ask for the manual directly from Sevcon. Contact the service dept. by email from their website.

Click to expand...

Still waiting to hear back from Sevcon. I have a feeling I'm too small for them to care about

Borg / Sevcon actively discourages any help be given to the DIY community.

That hostility extends also to their authorised third party service shops, distributors, dealers and OEM bike manufacturers

They only want to deal with those buying their product by the container load

someone buying them by the pallet would still be small potatoes.

Figured as much when I couldn't find any material online. That's why I gave up on waiting for their reply.

liveforphysics said:

Dragon 8 is a nice platform you would be glad to be running. Highest current density switched per package of any of the Sevcon/Borg options makes its burst power to mass ratio nice for LEVs.

Tuning it is not going to be very easy, but we've seen a few folks pull it off here with the Gen4 platform that is more complicated. That fact that its discouraging to you is a good sign that you could be aware of enough to pull it off with enough effort.

Remember the type of Dragon 8 you get can come in the Hall-sensor UVW style encoder, or the Sine/Cosine AB type, you are hosed if your motor encoder type doesn't match the controller type because its a hardware based difference.

Click to expand...

Any way to know by serial number which model you have?

If anyone's interested, I found this post here on ES with the official Sevcon Dragon 8 manual.

Well, just an update to "close" this post. I've managed to get the controller running.

Using the PDF in the previous message, and the pinout diagram (page 26) in it, I figured out the correct wiring for me. Without having module to connect the controller to my PC or anything else, using only the LED on the controller for "diagnostics" (note, the controller was programmed in advance for my motor and I didn't have any of the 4 passwords required to communicate to it)

M1 - Motor's blue phase line
M2 - Motor's Yellow phase line
M3 - Motor's green phase line
Pins 15 - short to Pin 23 since I have no other CAN modules on my bike (this was tricky to figure out. Kept getting 12 LED blinks indicating CAN error until I did this)
Pin 23 - shorted to pin 15 (see above)
Pin 1 - DC-DC converter V+ (12-24V range, 1A draw). Usually connected to key-switch, but I switch at other points in the circuit
Pin 22 - GND
Pin 2 - Hall sensor U
Pin 10 - Hall sensor V
Pin 16 - Hall sensor W
Pin 4 - Motor thermistor
Pins 18 and 11 - Forward (18) and reverse (11) toggle to ground
Pin 19 - Throttle hall-effect sensor (E49) voltage using reference to 5v output (pin 7)

I'm attaching the pinout diagrams here for the Sevcon Dragon 8, in case it helps someone