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While riding bike it loses all power, bike only has 50 miles on it, sorry for long story below, tried to give all details, Bike is new, and I do not know what’s normal . Something does not seem right.  Looking for everyone’s thoughts to understand if I have problem or this is normal.

100% charged battery I was on the bike for 3 miles, power assist 5, pedaling to assist, no pressing of throttle , speed 20 mph, very, minimal hills,  had just  coasted down a downhill at 25 mph, came to a stop at an intersection, when light turned green, I took off with throttle and bike lost power in 10ft, LCD shut off. 
I tried to turn on LCD, did not work.
I cycled the power switch, did not work. Shut power off, rode for a mile thinking a thermal protector maybe cut off power,  did not work. I folded the bike to totally disconnecting  battery, looking for a reset button, did not see one, put bike together, it powered up. this worked, for a short time until I touched the button for LCD and power cut again. Disconnected battery again and all was good.  UP TO THIS POINT I DO NOT FEEL I WAS PUSHING BIKE HARD

I did not touch LCD after it powered up, Pedal assist was at 2, went 10 miles, throttle pressed max, pedaling hard, minor hills here and there, I was behind schedule now (Friday night out with WIFEY and was already late, you know how it is) no further issue to this point. THIS 10 MILES I FEEL I DID PUSH THE BIKE REASONABLY HARD.  

I got to the final 1/4 mile steep grade to my home Battery was  at 4 bars at start of grade, I decided to move LCD to 5, maximum assist,  i did not loose  power. Pressed up the hill, speed decreased to 9MPH, near top, lost power again, I pushed bike to top, and put it away, without making an effort to get it working, several hours later went out and it powered up fine. 

Edited by Khalifornian
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I’ll move it but not a big deal but your synopsis is. The fact that your Sondors 350 Watt Bafang Geared HubMotor with a 36V Battery(?)  lost power and shut down after riding at Max Current Usage and Taxing the Motor on Hills at Full Power is probably the problem.  There are a lot of misconceptions about eBikes, especially with inexperienced riders on entry level ebikes... they are bikes and pedal assist vehicles. Pedal is the relevant word.  They cannot be expected to perform like eMotorcycles nor operated at their limits continually.  I believe that your expectations outdistance the reality of your bikes performance.  That being said the Geared Bafang Hub Motors are considered pretty bulletproof (seldom are burnt up, but heat is what destroys them and usage at continual high current combined with hills is the prescription for just such heat damage. The fact that your bike recovered, leads more to a function of the Controller’s or Batteries’ BMS (Battery Management System) actual circuit boards in both devices designed to protect them from dangerous parameters.  Hub motored ebikes, especially entry level bikes are not considered hill climbers. That’s Mid Drive eBike territory but of course mid-drives, have more power, better drive trains, more powerful batteries and controllers and cost a lot more money..  That’s the deficit  of riding hills.  To monitor your batteries capacity forget the bar gauge that shows little real information. Alway use the actual battery voltage. That’s the only accurate gauge of percent of capacity .  Your 36V battery at full charge show (42v), Battery might be unrecoverable below 31.3V and a function of the BMS is to shut down the battery before it gets that low. 

. Try operating your Fold at a less strenuous fashion and see if it behaves ...




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thanks for the info

it may be immaterial, and what you said probably pertains similarly.
if it makes and difference the spec on the bike are   below, we got the higher watt because of our hill up to the house .  
I get it though lug it down and you suck down the battery and things heat up  

I will put some more miles on it and see if it is an ongoing issue, 

What I thought was odd, was 10 miles, pedal assist set to 2, throttle pinned. and pedaling hard to help out, no issue

the 1st 3 miles were similar pedaling hard to help, except set to 5 maximum assist  

I am of the belief that the throttle gives you maximum assist regardless of the setting  on the LCD

heading up the steep hill, on Max assist , I totally get, and will work to understand the best way to go up hill  without destroying it  


SONDERS Fold XSSpecifications

  • Motor750 WATT
  • Controller20 AMP
  • Battery48V 14Ah Lithium-ion battery with Panasonic® cells

Maybe  you have a similar spec sheet for the higher volt battery

also, what do you do to monitor voltage, do you add a volt meter, some way? 

thanks for your help, once I get used to it. , I will be hitting you up on possible improvements for the bike. 

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 You Did Specify in the Title ...Fold XS, my bad. 

That does change my synopsis and raises my suspicions, since 7 speeds and 48V  x 750 watt power make quite a difference, but since your problems were always associated with max power and hills, let’s see if with a little more prudence when using power and riding with the idea of conservation of energy and see if any of the routes you ride, can be less vertically challenging  and find courses with suitable detours. Might be tough if you live at the top of a challenging hill.   I know that not what you’d like to hear but let’s see if any other anomalies surface besides failure at full power and steep hills that could point me towards another conclusion. I’m not at all certain now, that my deduction is the only possibility.  But there are hills and then there are HILLS!
In the mean time read thru Biknut’s posts about Buffy’s Fold Modifications.


Your XS has the newer KD718 color display and does not have the screen that displays the battery voltage like the 36V single speed’s KT LCD 3. I’m not knowledgeable about the accuracy of your battery percentage display indicator so I’ll have to assume it’s accurate and resolves to the chart below.  I just don’t have one.  

There are even other extreme upgrade possibilities for the Folds but let’s see what some more time on yours will reveal. 




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I am with you, i will put more miles of varied usage  and see how it goes. Truth be told this is my wife’s bike and I have ridden it to work 2 days so far, 13 mile  each way. My use so far 4 Trips   52 miles total  pressing it hard for the most part, I think I will be measuring battery voltage and checking component temperatures if issues come up.  

Day 1 Test 1, was how far will it go. RANGE ANXIETY I had an experimental electric MINI Cooper 8 years ago, I know range anxiety well. 
Wife said, take charger, I said no , I got this, I am known to be eternally optimistic.
 Got to work, used 2 bars (I agree it’s a pretty coarse measurement).  Perfect, 2 bars to get home, one left over, I am good. Heading home bike dropped to 1 bar 7 miles from home, I dropped power assist to 2 & slowed down, short time later the one bar started flashing & I slowed more,  No surprise to me, ran out of power on the uphill to the house. Darn thing is heavy, Ate crow,  called wife to be picked up . I was surprised I made it as far as I did  on the flashing one bar . 

25 miles of hard use, with advertised range of  40 to 60, no real surprise there

Day 2 test 2 was in my 1st post in this thread  and Really was no different than day  1, Rode hard and peddled hard. Difference was,  I charged bike before heading home and weather was a little warmer on ride home.  Issue was power cutting out 3 different times on way home. 
stay tuned. LOL

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Wow, that Mini Cooper sounds cool. Lead Acid? I’ve been curious what electric motors were used in early eConversions. I’ve read that Electric Fork Lift Motors, by some. I have a couple of projects planned. I have a 2013 Mongoose Beast Fat Bike that was gonna be my first ebike project before the Sondors Original was Offered and I’m planning on using some of my Sondors Originals’ Electrics to convert it. Two 36V canister batteries, mounted on a rear rack to produce a 72V pack is my goal.  I have the batteries off a couple of my those Original Sondors that are now 52V, My Black & White Lightnings. I’ll buy another 750Watt Motor, from Aliexpress on Nov. 11, I do each year on their Singles Day Holiday and the whole country is on sale. Less than 200$. But I’ve got so many other projects taking up time, it’s hard to work that in. Winters are better for eBike Projects.  
I grow a lot of Food for myself & my Collies. It does take considerable care every day, this time of year.

Your ride to and from work is about the same as my average ride on my daily route to and from town on my errands and my mail box. I only have a few Small Hills on my routes but I can equate to your situation. Ten years ago I would fly, with one of my Cannondale H400 bicycles to San Fran, Bel Mateo actually, where friends lived and I’d 0explore the city on bike. One of my favorite routes was over the foot hill from Belmont, on Ralston  Ave, to Half Moon Bay and Back. That’s about a 1000 ft elevation change. In San Francisco, I’d challenge my self on all the steepest hills....  up to Coit Towers, up the back side of Lombardi and down that famous hairpin street to the applause of tourists, and down the Embarcadero to and across the Golden Gate to Sausalito. Over to the Marin Headlands Park.  Some times I’d take the Ferry back Across the Bay, just for a change.  I was heart broken when my friends moved to Lovettsville, Virginia. But then again, that opened up new venues to fly to and ride. 
I’m not sure what your largest cog is on your set, but a 11- 34 will fit. That’s what I have on the rear of both my Electric Black & White Lightning’s. That might increase your advantage on the hills.... Kinda Radical and I don’t really recommend this, dare I call it an upgrade, but an All Wheel Drive Fold is quite possible and they do climb like a Monkey up a Coconut Palm. 






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Sounds like your a longtime rider who converted to ebike. I used to ride a ton, got hurt and never got back to it, Went for a couple rides, and was so out of bike shape I was over it. No ved on and became a gym rat, now a couch potato  LOL . The Sondor will be my stepping stone back into the sport . 
The MinieE Was a BMW development car, had Lithium Ion battery, what’s funny, I had several instances just like I had on the bike cutting out, zipping along in fast lane, motor cuts out, regenerative braking kicks in while I am trying to get to shoulder. It would not reset, and had to be towed to dealer. Fun car, a lot of range anxiety though.
Your garden looks cool, my wife has been ramping up our garden  it’s a lot of work for her,

As far as the gearing it’s all stock, I will look into the gearing, does anyone ever put  a front detailed with multiple chainrings on the bikes, I could use higher and lower gearing. Also if I was able to get into the LCD controller, are there setting I can adjust to improve the bikes operation. 

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 Yes, you can follow the threads on reprogramming your Controller’s options  here. I have no experience With the KD718 but a lot of the member’s created info, is scattered in threads through the forum.  I do know that the advanced settings require an Admin Password and it’s different for different Sondors Models.  A lot of members consider their Sondors model the only one and don’t need to be correctly identified when polling the forum and that can make identifying their postings of their info, slightly difficult to correlate. 
Standard Front Derailleurs don’t fit on the wide Bottom Brackets Bike’s Seat Post Tube mount, at least on the Fat Bikes, but the one that mount to the Bottom Bracket ‘s Lock Ring, are a type "e". There have been a couple of reported front derailleurs mounted on the Fat bikes on forum and if I remember, at least another double front chainring installation that was manual, stoping and physically moving the chain by hand from one ring to the other, then continuing.  No Triples Reported.  


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Bike cut out again, this time , easy ride, 1 mile

after cycling battery switch and turning on LCD 

error code 24 fault with motor Hall Sensor

bike still under 1 yr warrantee, thought I would ask here 1st . Suggestions welcome  

i have not contacted SONDORS other than to purchase, being lazy here, but does anyone have the best way to contact SONDORS for issues

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  • 10 months later...

I'm having a similar issue on my 2 months old Fold XS. The power to throttle and pedal assist cut out for about a minute. No rhyme or reason to it. The LCD stays on but everything else cuts off. No error messages, just loss of power. Any assistance would be great. I've out two tickets in with Sondors support and have not heard back. Great product. I'm really hoping someone here can help me out. 

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The most likely problem, with your symptoms that is surfacing lately, is Brake Lever Cut Out switches.  Make sure your brakes are properly adjusted and lever closes completely.  There is a set screw to adjust the cut out switch.
Alternately, when it occurs you can check by unplugging the brake cut out cable at it’s Higo connector, one by one to see if power is restored. 



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  • 1 month later...

I have a similar issue on our Fold X.  We got it in January 2019 and only have 297 miles.  For the past 6 months the pedal assist power cuts out, with no error messages.  I'll be pedaling with pedal assist level 2 on a relatively flat street, hear a loud clang, and the pedal assist power cuts out.  If if press the brake controls or turn the LCD off and on, clang, the pedal assist power comes back on.  I tried disconnecting the LCD and plugged the cable with the shunt; the power cuts out less often, but it did cut out.  I've been working for several months with a friend who has 5+ SONDORS to debug, with no luck so far.  He replaced the brake pads, adjusted the brake controls, and has adjusted the ring with the magnets by the sprocket.  I see you think on Dennis Villa's post that it could be Brake Lever Cut Out Switches?  My friend adjusted those screws I believe, but I will double check.  To try the alternate method, if I unplug the brake cut out cable, will I still have brakes if I try to road test it?

I have logged a ticket with SONDORS for a tech consultation, I made the appointment, but the tech guy never called me at the appointed time.  I tried again and am waiting to hear back.  Feeling frustrated; I want to ride, not debug, the bike!  

Thanks for your help....


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Yes. But if power returns, it won’t cut off when you use the brakes unless you stop pedaling, and don’t use throttle, like a motorcycle. 
‘It’s the most frequent cause of No Motive Assist, but LCD has function.  The Clang is problematic and might suggest a dislodged motor magnet. No error code for that … until it causes internal damage to wiring.  
Tell Sondors Technical Care, Reddy Kilowatt Sent You. 




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