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Universal E-bike repair solution


1 µW
Oct 11, 2022
Dear users of this forum,

My name is Matthijs Rombout and I am a bicycle mechanic from the Netherlands.
I have a problem with electric bicycle repairs and I hope you can help me with the solution.

I get a lot of people in the shop with old electric bicycles that do not work anymore. They are quite desperate because every other bicycle shop has already told them they cannot repair their e-bike because it is to old.
The problem is that the original manufacturers stop selling parts for these older bicycles and people are not willing to invest in old electronics if another (unreplaceable/ hard to find) component might brake down in the near future. The bicycles themselves are often in great shape and can last several more years, but the electronics are old and need to be replaced.

New universal electronics. This set will consist of: controller, display, sensor (if necessary), BMS (if necessary)
The idea is to replace the original controller for a universal controller and a new display (to avoid communication problems).
If possible I would like to keep the original PAS sensor and Battery. If the battery BMS has special software that prevents it from working with other controllers, then I can replace the BMS for a new one.
Also I would like to keep the original motor, if hall sensors are broken then we can use a sensorless controller.

I have a basic understand about all the electronic components and looking for a solution I came across this forum. Some of you have an incredible deep understanding of all the electronics and I am amazed by the topics discussed.
I am hoping you can help me to find suitable electronics for the job and answer some of the qestions I have, like:
-Is it possible to have a universal controller that works with all different motor types? (direct drive, geared hub, mid drive)
-Is it possible to have sine wave universal controllers, or do they need to be square wave?
-What are good brands for controllers?
-What controllers are good value for money?
-Where to place the new controller so the bicycle looks decent?

Any advice or tip is welcome!
It might be possible to use a sensorless controller, and that would eliminate issues with sorting the five wires to the hall sensors. The color codes on the wires, and the order of the code wires will be different between various manufacturers.

Theres are several models, and once you find one that you like, then you can specify the other components.

I would suggest that the first controller you try is the Tong Sheng. That is the controller in the TSDZ2 mid drive, and I have been told it is easily programmable.

It might not work for your uses, but then again, it might work well.
Grin Tech's controllers have a computer app that lets you configure it for different motors. Super expensive, though.

Grin Tech also uses a bizarre PAS voltage better used for torque sensors, so requires an adapter to use existing cadence PAS sensors. Right now my bike has both voltages of PAS sensors slapped on it due to that.

Other cheaper controllers have a learning cable and a manual procedure to try to determine the hall sensor order. Similarly there are dual mode controllers that can run with either sensors or not.

I'd just stock entire conversation kits, maybe some without motors, and sell those as needed to repair old ebikes. Controllers typically aren't cross compatible with different LCDs.
The Grin Technology Phase Runner motor controllers have been installed on a variety of motors from Golden Motor Magic Pie (geared hub) to Bafang BBS02 (mid drives). The typical display used with these displays is a Grin Technology Cycle Analyst. They are well documented, very programmable and can be adapted to most any 3 phase BLDC motor. The problem with these is that they are expensive and frankly the display technology used by the Cycle Analyst is obsolete. None the less they are the proof that what you are trying achieve can be done.

A more economical and practical approach might be a matched KT/Kunteng motor controller/display set. They are fairly common, reasonably priced and marketed by a number of vendors. The problem with any Chinese E-Bike components is they are very poorly documented and the Chinglish documentation can be very difficult to to interpret. The manufacturers may also suddenly decide to change the design, wiring or firmware without bothering to tell anyone (including their own technicians and vendors). The good news is that there is an open source project for firmware for KT Controllers. See this (rather long) thread: https://endless-sphere.com/forums/viewtopic.php?f=30&t=87870

The Grin Technology Phase Runner https://ebikes.ca/product-info/grin-products/phaserunner.html
Grin Technology Cycle Analyst https://ebikes.ca/product-info/grin-products/cycle-analyst-3.html
KT Displays https://www.greenbikekit.com/catalogsearch/result/?q=KT+Display
KT 24V 36V 250W sinewave controller https://www.greenbikekit.com/250w-brushless-e-bike-controller-lcd-display.html
KT 36V 48V 350W sinewave controller https://www.greenbikekit.com/350w-36v-48v-kunteng-kt-ebike-hub-motor-sine-wave-controller.html
KT 36V 48V 500W sinewave controller https://www.greenbikekit.com/kunteng-kt-48v-36v-500w-motor-controller-for-lcd-led.html
The solutions above are certainly good compromise solutions depending on the situation, but to try to answer the original question of a universal solution, with some notes. Some of it you may have already run across or thought of, but I'll put it down while I'm thinking about it:

A truly universal solution doesn't exist, because the solution required depends on the specific features and operational modes of the bike in question that the rider actually wants to keep, and how much it costs to do this vs just getting another bike.

It also depends on the power levels required. A low-assist 250w (or less) system, especially a middrive of that power, doens't need nearly as big and expensive a controller as a direct drive "500-1000w" system.

There isn't any single system that has all the possible ways of working built into it (one could be made, but doesn't presently exist--the closest thing might be the previously-mentioned Cycle Analyst added to a controller appropriate to the specific motor system / usage scenario).

Whether any parts already on the bike (sensors, lights, etc) work with a new controller system will depend on what they are and how they work. It's fairly likely that they would, or could be made to, but not universally.

Batteries...they are probably the most common reason old bikes don't work. The battery ages and wears out, doens't hold a charge, fails in some other way, and the bike begins either misbehaving or it stops working entirely.

If the battery does still work...how long is it going to still work? Will it be worth repairing a system problem, if it'll "soon" need several hundred dollars worth of battery replacement?

If the battery is fine and not aged, expected to last...the new system will need to be the same power level as the old one (or less) for the battery to continue working the same way and not potentially be overloaded (which may cause shutdowns when less than full, for instance).

Most (but not all) motors found on a typical ebike will be the same general kind of 3-phase brushless motor and will probably work with a typical controller. But not all of them will work, eiher because they use a different kind of position sensor (in which case a sensorless will usually work) or because they built them enough differently from the usual for some specific system reason that they need the controller to be tuned to work with them in some way.

Some motors on old ebikes are brushed motors, and will need a completely differnet kind of controller; these are not that common, but if your goal is to fix up old bikes, you're bound to run into some eventually. :)
Your quest is only possible in a market where the incoming bikes are similar to each other.

Otherwise maybe a selection of 2-3 "kits" would work to cover 80+%

However maybe a change of "business model" would create both happy customers and higher profits for you.

Build a relatively inexpensive (to you) "generic DIY" ebikes, uniquely advertised as easy to maintain, repair, upgrade over the long term.

Very green, frugal, "buy it for life" will be a compelling selling proposition compared to the very resource-wasteful big manufacturers.

Maybe 2-3 models to give some choice.

Rather than offering to repair these incoming old broken bikes, offer a "trade in" price, and convert them to your "standard" BIFL model.

Then, for those that are worth repairing, you can take your time sourcing parts, testing etc until you know it's reliable, then sell it on as refurbished.

Maybe contact the previous owner if they prefer they can buy it back, give them a trade-in price off their "standard BIFL" unit depending on its condition.

Maybe also develop leasing / rental / rent-to-own programs...
john61ct said:
Very green, frugal, "buy it for life" will be a compelling selling proposition compared to the very resource-wasteful big manufacturers.

It's difficult to get manufacturers interested in that kind of thing. Even products that used to be long-lived (e.g. kitchen appliances) now have short service lives because that's better for business.
The high end Bosch/Yamaha mid drives are designed not to be repaired by non-factory. That still leaves the many hubdrive bikes where you can replace the controller/display and/or motors. You don't have to wait for a universal solution. Just pick a controller and display family that you like, and replace what's needed.

I'm just a hobbyist, but it was trivial to put replace the controllers in two store-bought ebikes I had with KT controllers and displays. The bikes ran a lot better too, with a better pedal assist choices.

The business model problem is will people want to pay $200 for new electronics, or $200 for a new motor. Battery replacement will require good liability coverage.

Well, maybe they will pay. After doing at least 200 oil changes myself in 40 years, I'm forking over $80-100 to the oil change guy because I no longer want to crawl under my cars. It's also synthetic Mobil 1.