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Understanding Parts Compatibility for your SONDORS eBike

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Over the last several years SONDORS has evolved the electrical systems of their bikes from open/generic Bafang to several different proprietary set-ups. The purpose of this document is to briefly explain each generation of bike and explore the issue of parts compatibility for upgrades and repairs.

The original "Original" (Generation 1)

In 2015 the SONDORS e-bike was born after backers on crowd-funding site Indiegogo waited for up to half a year for the first $499 e-bike. There was only one bike, and it came in a few different color combinations. The bike was single speed and there was no LCD available until months later, and shipping was $174 extra. It used an 8.7Ah bottle battery and there were no extended batteries available except from third party vendors months later. All of the bikes used the standard 3-LED, 6 pin throttle still in use today on single speed bikes.


These bikes are easily identified from a few visual clues:

  • The words “e-bike” printed on the battery box under the original SONDORS logo (see pic)
  • The etched controller serial number does NOT have the letter “U” at the end
  • They came in only a few colors that were never produced again – Yellow with orange anodized aluminum wheels, Black with red wheels and printing, and Black with yellow wheels and printing


These bikes used a generic controller, which makes them the only SONDORS bike where you can add an aftermarket generic LCD (like the KT-LCD3) root_November25_1543159498_CWSondors_Compatibility_White_Paper.pdf_-_Adobe_Acro.png.b4b9b2a82effe55076a3fd00bfcee49f.png
without replacing the controller. It also easy takes a 20A or 25A controller upgrade, which again will work with the stock throttle and any aftermarket or SONDORS LCD (available later in the year) that works with the SONDORS controller.

When SONDORS started shipping an LCD, it said SONDORS on it even though it used generic protocol. This is why you can’t tell what bike you have based on whether or not it says SONDORS on it.




The  Kickstarter Generation (Generation 2)

Following a successful and disruptive IGG campaign, SONDORS did a follow-up campaign through Kickstarter. These bikes were mostly sold and distributed in 2016 and into early 2017, and came in a wide range of unique colors (Caribbean blue, gray, pink, and others), and new options. They still used the bottle battery, but you could now get an aluminum frame bike, an extended range battery, 4.0in tires, and even first-generation front shocks. They were still single speed, but they abandoned the generic controller for a proprietary one, which started the complicated path of compatibility.


A lot of bikes fall into this generation, and again there are some visual clues

  • No more “e-bike” printed on the battery box
  • The etched controller serial number now contains the letter “U” at the end, signifying a new, proprietary controller.
  • The bike will also have a bottle battery and not a newer triangle battery
  • The bike on the right is a 2nd generation SONDORS fat bike with optional shocks, 4.0 inch tires, and an aftermarket black trim kit and Ibera RA5 rear rack.


This is the beginning of SONDORS using a proprietary protocol for their controllers. If you have one of these bikes and want to keep the stock 15A controller, the only place you can get an LCD is from SONDORS. Your bike will run using an aftermarket LCD like the KT-LCD3, but the display will be wonky. It may not show speed, the PAS controls might not work, and the battery level display won’t be right.

Most owners with these bikes wanting an LCD (it wasn’t included) choose to swap out their controllers for an aftermarket 20A or 25A version (around $55-$65) and add a generic LCD for around the same price. The 3-LED throttle works fine with these aftermarket controllers. Because these bikes have a 350W motor with the smaller plug, going above 25A will usually require a motor swap and usually an upgraded battery at no small cost. Many people do 48v or 52v upgrades using huge, aftermarket triangle batteries for higher top end speed and more range than the average butt can handle.

The first SONDORS direct generation (Generation 3)

This could actually be 2 or 3 generations with all of the changes happening, but from a compatibility standpoint I’ll lump them all together. Following the IGG and KS crowdfunding campaigns, SONDORS took ordering in-house. They started with a bike that looked just like the KS bikes but with some new colors (including red and royal blue) and also included a bottle battery. For ease, I’m going to include those bottle battery bikes sold direct into the Generation 2 bucket because technically they’re similar. However, as 2016 turned into 2017 SONDORS started introducing triangle batteries, gears, the Thin, Fold, and even the X bikes. This generation used the proprietary KT-LCD3 LCD with SONDORS printed on it, and maintained the proprietary 15A controller with the “U” in the serial number. However, this new controller now had different plugs for the new triangle and fold batteries which added some complexity.

This is also when SONDORS introduced 7 speed bikes, which also introduced a proprietary 3 pin throttle. These 3 pin throttles look similar to the Bafang BBSHD throttle, BUT the pins are male instead of female. This is to keep owners from plugging the throttle into the PAS plug on the controller. These throttles are only available from SONDORS, although you can sometimes find them for sale by owners that have swapped theirs out.


There are so many bikes that fall into this generation you are better off using process of elimination. If your bike has a bottle battery, it’s either Generation 1 or Generation 2. If your bike has a triangle battery AND a rectangular LCD based on the KT-LCD3, you fall into this generation.

The picture on the right is a SONDORS-KT LCD3 LCD.


This is where compatibility gets “fun”. Like with previous SONDORS bikes that are not “Generation 1”, aftermarket LCDs will not work with the stock 15A controller. The bike will run, but the display will be messed up. Here are some key points:

  • If you want to keep the stock controller, you will need to get the replacement LCD from SONDORS
  • If you want to upgrade your controller to 20A or 25A, you will need a new, aftermarket LCD. You can get the tried and true KT-LCD3, but one of the known vendors is now selling a compatible color LCD for around $20 more.
  • If you upgrade the controller, you will need to get one with the correct battery connector, OR transplant the connector from your old controller to your new one. Most generic controllers are just 2 wire
  • If you have a 7 speed bike, you will also need to replace the throttle if you upgrade the controller. This is because the aftermarket controllers use the 6 pin throttle and not the SONDORS 3 pin version
  • If you need a new throttle for a single speed bike, you can get a generic 6 pin throttle from known vendors. If you need a new throttle for a 7 speed bike, you have only a couple of choices – buy one from SONDORS, or swap out the controller, LCD and throttle to something generic and not proprietary
  •  Another option is a brand new upgrade kit available form SONDORS. This includes an upgraded controller and color LCD for around $200. If you get the right kit the LCD will be set correctly and it will be compatible with the throttle

Easy, right?

Current mid-2018 Generation (Generation 4)

In mid-2018 SONDORS switched out the controller and LCD for a new square version called the KD51C-KDS (aka KD51). This new display is completely different under the hood, and it’s gotten mixed reviews. People like that you can adjust PAS power levels, but many dislike that you can no longer see voltage on the display. All bikes during this generation were changed. They all still have triangle batteries, but the controllers and LCD for the “Original” (yes, the name is confusing), Thin, Fold, X, Sport and Mini are all changed.Image_005.jpg.1e0d98f62d9131f4e0e81ba26a3a2f3e.jpg


This one is easy. If you have a KD51 LCD, you have what we’re calling a Generation 4 bike. The picture on the right is the KD51.


All of the compatibility notes from Generation 3 still apply, but it’s also important to note that none of the previous generation controllers are compatible with this LCD, and none of the previous generation LCDs (or generics) are compatible with the Generation 4 controller.

  • You still need to be aware of the single speed versus 7 speed throttle compatibility with this new controller
  • While Generation 2 and 3 LCDs and controllers are interchangeable with each other, neither are interchangeable with Generation 4
  • This is why many with LCD, controller or throttle issues choose to go towards generic again unless covered under warranty by SONDORS.
  • Like with previous generations, SONDORS now sells an upgrade kit for around $200 that contains a new color LCD and either a 20A or 25A controller depending on the bike. These kits will also not be compatible with aftermarket parts, but it will maintain compatibility with your throttle if you get the right kit.

November 2018
1.0.0 - Mike Ritchie

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Is there a way for the owner to differentiate  Sondors X 2017 or newer models from Sondors X 2016 or older models ... The completely new LCD screen (this here https://sondors.com/search?type=product&q=Color+LCD) will only fit to 2017 models or newer.

Interestingly even the Sondors chat couldn’t tell me at once if I own an 2017 model or an older one 😕🙁☹️ .

OK I’ve got a ticket and they will contact me ... but (to be honest) I’m not sure if I can rely to their statements. Sounds a little bit confusing ...

Edited by George-X
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George- X, there were no Sondors X in 2016.  The compatibility of LCD screens is now a complicated issue with individual protocols for different models. The easiest and best solution is to buy both; an aftermarket LCD, and new, better, more powerful controller for less than the price of the Sondors Color LCD.  The new Bolton Color LCD 8H & their 25 amp controller are the pinicle of easy upgrades and take you to the next level of performance for less moola.








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  • 1 year later...

Gents, Gen3 Sondors X Europe issue,

since I broke the LCD (KT-LCD3), I have tried to find out which one to replace it with,

BUT unlike it says above about Gen3, the controller I have does not have letter U in the end..see pic below.

The LCD came with lettering Sondors on it, which sounds like it is a Sondors special?

This means, at leat this one, shipped end 2017 to EUROPE, is not typical Gen3 with proprietary controller, right?

I bought the bike new, directly from Sondors back in 2017, May, June or so. Preorder campaign, EUR version.

I believe this X was same for all EUR countries, with max 350W motor, 25 km/h speed and as it looks like, 7*48=336W rated power as well.

Well it does get as high as 500W with pas 5, but the motor marked as 350 is the key.

So any aftermarket KT display should do?



Edited by Juha Tuomola
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This is a quandary and doesn't match anything I can find, including my own 1 & 3 generation Sondors controllers. 
‘What you have is a 48V controller of only  7Amp rating.  That would not be typical for any US market Sondors.  I have to ask if you have gotten your Sondors Used or from the Kickstarter Campaign? 

I can’t attest to what might have shipped to Europe and but Sondors does not feature that controller for a 3rd generation . I have one and it’s a KT36ZWS-LDO1 .

My assessment would be that your controller, "probably", does not have the proprietary communication protocol and if your LCD does not have the word Sondors on its top border, neither does it.  I’ll preface that by saying, I think some early Sondors LCD’s with the proprietary communication protocol, didn’t have Sondors printed on them. I’m thinking either you don’t have a 3rd gen Sondors and / or your controller came as aftermarket from China and not Sondors. 

But there is one sure way to eliminate the quandary (I don’t think anyone at Sondors.com can quantify where your controller came from) and that’s to replace both your LCD & Controller with an aftermarket pair from Electrobikeworld.com. As always clear and concise communications are mandatory when communicating your needs with any of our aftermarket Sondors Vendors. Nick can get you what you need. 



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Thanks. Updated some details in the original post.

I mostly run pas with low level for good exercise and long mileage, would not want to invest in e.g. 20-25Amp controller as it would (?) raise the pas power levels as well, if they are not changeable by setup..?

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Yes you can manipulate PAS delivery levels in setup although I don’t remember exactly what that particular setting is.  And Motor manufactures rate their motors at whatever watt numbers support their marketing goals. Their rating is not like a light bulb that uses a static number of watts at a given voltage. Your 250 watt Bafang is exactly the same motor as my 350 watt Bafang, only the names have changed to protect the innocent, I mean fit within EU guidelines by relabeling the case. My 350w Bafang with its 25Amp controller runs quite happily on its 52V battery @ over a1000watts on PAS 5 or full throttle. Of course I cruise  in PAS 1 at 20-22 mph / 32-35 kph, that’s the sweet spot for my cadence, leg speed and gearing. I ride for the same reason you do, healthy exercise and every watt you don’t use is one you don’t have to replace. I ride quite regular routes between 22 to 42 miles. If I need to go more distant I take my lightweight Electric White Lightning to the train into the DFW MetroStool and ride to my destination. 

Without changing to a higher voltage battery and with careful battery management (like mega milage car driving), I found switching to the 25 Amp controller well worth the investment and the advantage is mostly more torque &  acceleration with a few more mph/kph top speed. Besides the aftermarket KT-LCD3, before Sondors sold them, the 25Amp controller was my first upgrade. Still use it on my EWL. 
I’m not sure anyone besides Storm Sondors could tell you if your broken LCD and controller have the Proprietary Communication Protocol  but it probably depends on the exact manufacturing date for your Custom.

Gena Davis portraying a Valley Girl from the movie "Earth Girls Are Easy. 


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