Help! My pedelec suddenly got faster (SameBike JG20, YSDX20, XW-20ZC) - long text!

[Craigs]

So I got your attention, that's great!
First and foremost: this is a TRUE story, as weird as it may sound. I searched the internet, contacted the company (thanks, David Hou @Samebike, for ignoring my support request!), nobody ever mentioned what I experienced.
Then I asked for help in a German eBike forum, was ridiculed and flamed by some, got a 'semi' explanation, but no real solution for the core issue.

BTW: I am also the author of the only (AFAIK) detailed review and test of this specific Chinese "Samebike JG20", published by a German GadgetWelt forum. Interestingly it was written up BEFORE the weird change occured. I liked it more prior to its weird behavior.

In a nutshell:
I own one of apparently very few Samebike JG20 foldable eBikes (sometimes sold as XW-20ZC or YSDX20). My unit is the UK version, based on the power plug: 36V, 250W, 8Ah battery pack. I use it in Germany.
It is my first (most likely last) pedelec; I have nothing to compare it with. 'Learning by doing'.

Out of the box it appeared a little weak for the promised 250W, also it did not reach the advertised speed of 25km/h: in both modes (assist, moped) it would run exactly 20km/h. You could hear the motor throttle "whine" cutting at that speed. As it is a foldable 20" bike with a 6spd Shimano shifter this speed was equivalent to a cadence of about 72rpm at the crank. I quickly got used to this. Actually enjoyed this speed and got an acceptable 50-54km out of the 288Wh/36V battery. Life was good.

AND THEN IT HAPPENED:
after three full battery charges (ca. 150km total) the bike - on its own - changed its behavior and performance whenever powering it up as usual:
it was way more zippy, accelerated with more gusto, and now reached precisely 25km/h! Again both with and without pedal assistance it would accelerate to 25% higher speeds than previously.
While this matches the specification, this change came with three major disadvantages:
- the range of the battery dropped significantly, from 50+ km to about 40-43km
- as this cheap ebike apparently has NO power step control I MUST ride at 25km/h instead of 20km/h. Anything below will engage the motor to accelerate, as long as I move the pedals. It is now a 'hit and miss' bike: pedal a little to reach 22km/h, stop pedaling and wait until the motor stops pushing and the speed drops to 18km/h, pedal again to get so the motor kicks in - a little ridiculous, no?
- the gearing ratio of this 20" bike is not tuned to this speed of 25km/h. That's equivalent to around 90rpm at the crank, not 'geezer like' as I want to. Kids may pedal along this way, not me.

As a novice and retired engineer I had 1 (and only ONE!) reasonable explanation for this unexpected behavior of my Samebike: apparently it had used and finished a 'run in' phase (conditioning), as most mechanical motorized vehicles (cars, motorcycles) require. To settle tolerances, adjust electronic power controls, learn battery discharge curves etc.
So I asked about this in a German pedelec forum: they laughed at me, called me a stupid engineer with no clue about Li batteries (OK, they do NOT require a conditioning, but my ebike DID this!)
To cut a long story short: the best explanation I received was:
- your bike was broken when it arrived
- it magically healed itself after (exactly!) three battery charges
- the fix increased the speed (power?) by exactly 25%
- the controller must have sensed an error and reset itself to match the bike's parameter on its own
- live with it
mmh..
I WANT THE ERROR BACK!!

Nobody knew how to 'talk' to the rare and cheap China made controller, how to 'fiddle' with it.
Apparently these Chinese controllers have a Rx/Tx serial port, but who would know such a protocol and parameter setting - hopeless.
Many suggested to buy a better (multistep power) controller and handlebar unit; or throw the entire junker away; great advice..

Out of desperation I dismantled (against my rules) the brandnew bike, opened the installed controller, photos attached.
When searching the internet I did find ONE similar model: apparently the Samebike XMZ1214 uses a controller "X863-AA006" (I have "X863-AA004"); with a neat handlebar display AND power control buttons that I do not have - wish I did..

Now to my main questions:
- can I 'tweak' this controller back to what it COULD do originally: i.e. assist only to V<=20km/h?
- does the built-in controller X863-AA004 allow for power step control (+/- buttons on the handlebar) by replacing the simple 'Saxin' unit without LCD display and buttons?
- the 'Saxin' handlebar control has two 'indicator LEDS'; only the left one is ON when turning the power key; the right one flashes shortly, so it IS alive. What 'should' it indicate; maybe the alternate 20mph/32km/h mode as used in the USA? Not that I want this bike to run 32km/h, God forbid..
- has anyone figured out how to 'talk' to this specific controller, e.g. by brake/PAS/horn/light activation sequences during the power up cycle?
- Could the 'better' controller/display package for the Samebike XMZ1214 be obtained on the market? Would it fit, probably needing more than the currently installed five wires to the handle bar control?
- any other ways to throttle the assistance during pedal assisted rides? My current solution:
I unplugged the PAS as it would otherwise override the moped gas control at any speed. Now I use the gas control to set it to my speed and pedal'under load' along with it. This allows for pedal assisted riding at any speed up to Vmax, but I have to hold the gas grip like on my motorcycle, Mileage in this mode has not been checked so far.

Ok, it IS a long story, but then: it IS about the most crazy problem a pedelec can have:
everyone is asking for advice how to speed it up, I WANT IT TO BE AS SLOW AS IT ONCE WAS!!

Attached a few photos of my (customized) Samebike JG20, simple 'Saxin' handle bar control unit and the main controller.

I'd LOVE to hear from other owners of this JG20 (or its similar Samebike derivates). I want to know about their experiences, about anything to make this freaky '6 speed pedal, 1 speed motor' pedelec a little more useful!

Thanks so much for reading this far!
And pardon my 'German English'; I tried my very best to keep it entertaining AND informative at once. Whoever finds spelling errors may keep them - for free!

 

[flecc]

I think the most likely possibility is that the cells in the battery were out of balance when you first received it, resulting in it having low voltage so both slower and weaker performing,

At each charge the battery's own internal BMS* takes the battery to full charge and then balances the cells, probably failing to fully achieve that in the first two charges but finally achieving it with the third.

Then with both full voltage and capacity, the bike was able to reach the design speed and performance. You'd need to add a throttle to be able to have lower speeds, perhaps someone with knowledge of that controller could advise if that is possible.

*BMS = Battery Management System.
.

 

[vfr400]

Too much to read. I don't have that level of concentration anymore, nor the time. I got as far as David Hou. Send him my regards.

From the title, I'd guess that you don't understand how the levels on your controller relate to speed control.

 

[RossG]

Don't these bikes have the "restriction wire" in the controller? if so maybe it's become unconnected and thus no more speed restriction....rejoice!

BTW, who's Hou ??

 

[Craigs]

Too much to read. I don't have that level of concentration anymore, nor the time. I got as far as David Hou. Send him my regards.

From the title, I'd guess that you don't understand how the levels on your controller relate to speed control.

There are none, that's what I tried to explain. It would not have bothered me if the bike had maintained the original, comfy top speed.

 

[Craigs]

I think the most likely possibility is that the cells in the battery were out of balance when you first received it, resulting in it having low voltage so both slower and weaker performing,

At each charge the battery's own internal BMS* takes the battery to full charge and then balances the cells, probably failing to fully achieve that in the first two charges but finally achieving it with the third.

Then with both full voltage and capacity, the bike was able to reach the design speed and performance. You'd need to add a throttle to be able to have lower speeds, perhaps someone with knowledge of that controller could advise if that is possible.

Don't these bikes have the "restriction wire" in the controller? if so maybe it's become unconnected and thus no more speed restriction....rejoice!

BTW, who's Hou ??

Hou is (according to the internet ) the main rep on Samebike's site, the only person and email I could find. China is not really known for customer/warranty support, so I am not that surprised.

Yes, I'd LOVE to see where on the circuit board such a thing is - can you point to it?
But: the 'wrong' initial speed was 20km/h, now it healed itself and runs the specified 25km/h. The only optional speed (for US markets etc)is 32km/h, even FASTER than my one can run.
This does not explain the behavior, from my point of view.

 

[Andy-Mat]

So I got your attention, that's great!
First and foremost: this is a TRUE story, as weird as it may sound. I searched the internet, contacted the company (thanks, David Hou @Samebike, for ignoring my support request!), nobody ever mentioned what I experienced.
Then I asked for help in a German eBike forum, was ridiculed and flamed by some, got a 'semi' explanation, but no real solution for the core issue.

BTW: I am also the author of the only (AFAIK) detailed review and test of this specific Chinese "Samebike JG20", published by a German GadgetWelt forum. Interestingly it was written up BEFORE the weird change occured. I liked it more prior to its weird behavior.

In a nutshell:
I own one of apparently very few Samebike JG20 foldable eBikes (sometimes sold as XW-20ZC or YSDX20). My unit is the UK version, based on the power plug: 36V, 250W, 8Ah battery pack. I use it in Germany.
It is my first (most likely last) pedelec; I have nothing to compare it with. 'Learning by doing'.

Out of the box it appeared a little weak for the promised 250W, also it did not reach the advertised speed of 25km/h: in both modes (assist, moped) it would run exactly 20km/h. You could hear the motor throttle "whine" cutting at that speed. As it is a foldable 20" bike with a 6spd Shimano shifter this speed was equivalent to a cadence of about 72rpm at the crank. I quickly got used to this. Actually enjoyed this speed and got an acceptable 50-54km out of the 288Wh/36V battery. Life was good.

AND THEN IT HAPPENED:
after three full battery charges (ca. 150km total) the bike - on its own - changed its behavior and performance whenever powering it up as usual:
it was way more zippy, accelerated with more gusto, and now reached precisely 25km/h! Again both with and without pedal assistance it would accelerate to 25% higher speeds than previously.
While this matches the specification, this change came with three major disadvantages:
- the range of the battery dropped significantly, from 50+ km to about 40-43km
- as this cheap ebike apparently has NO power step control I MUST ride at 25km/h instead of 20km/h. Anything below will engage the motor to accelerate, as long as I move the pedals. It is now a 'hit and miss' bike: pedal a little to reach 22km/h, stop pedaling and wait until the motor stops pushing and the speed drops to 18km/h, pedal again to get so the motor kicks in - a little ridiculous, no?
- the gearing ratio of this 20" bike is not tuned to this speed of 25km/h. That's equivalent to around 90rpm at the crank, not 'geezer like' as I want to. Kids may pedal along this way, not me.

As a novice and retired engineer I had 1 (and only ONE!) reasonable explanation for this unexpected behavior of my Samebike: apparently it had used and finished a 'run in' phase (conditioning), as most mechanical motorized vehicles (cars, motorcycles) require. To settle tolerances, adjust electronic power controls, learn battery discharge curves etc.
So I asked about this in a German pedelec forum: they laughed at me, called me a stupid engineer with no clue about Li batteries (OK, they do NOT require a conditioning, but my ebike DID this!)
To cut a long story short: the best explanation I received was:
- your bike was broken when it arrived
- it magically healed itself after (exactly!) three battery charges
- the fix increased the speed (power?) by exactly 25%
- the controller must have sensed an error and reset itself to match the bike's parameter on its own
- live with it
mmh..
I WANT THE ERROR BACK!!

Nobody knew how to 'talk' to the rare and cheap China made controller, how to 'fiddle' with it.
Apparently these Chinese controllers have a Rx/Tx serial port, but who would know such a protocol and parameter setting - hopeless.
Many suggested to buy a better (multistep power) controller and handlebar unit; or throw the entire junker away; great advice..

Out of desperation I dismantled (against my rules) the brandnew bike, opened the installed controller, photos attached.
When searching the internet I did find ONE similar model: apparently the Samebike XMZ1214 uses a controller "X863-AA006" (I have "X863-AA004"); with a neat handlebar display AND power control buttons that I do not have - wish I did..

Now to my main questions:
- can I 'tweak' this controller back to what it COULD do originally: i.e. assist only to V<=20km/h?
- does the built-in controller X863-AA004 allow for power step control (+/- buttons on the handlebar) by replacing the simple 'Saxin' unit without LCD display and buttons?
- the 'Saxin' handlebar control has two 'indicator LEDS'; only the left one is ON when turning the power key; the right one flashes shortly, so it IS alive. What 'should' it indicate; maybe the alternate 20mph/32km/h mode as used in the USA? Not that I want this bike to run 32km/h, God forbid..
- has anyone figured out how to 'talk' to this specific controller, e.g. by brake/PAS/horn/light activation sequences during the power up cycle?
- Could the 'better' controller/display package for the Samebike XMZ1214 be obtained on the market? Would it fit, probably needing more than the currently installed five wires to the handle bar control?
- any other ways to throttle the assistance during pedal assisted rides? My current solution:
I unplugged the PAS as it would otherwise override the moped gas control at any speed. Now I use the gas control to set it to my speed and pedal'under load' along with it. This allows for pedal assisted riding at any speed up to Vmax, but I have to hold the gas grip like on my motorcycle, Mileage in this mode has not been checked so far.

Ok, it IS a long story, but then: it IS about the most crazy problem a pedelec can have:
everyone is asking for advice how to speed it up, I WANT IT TO BE AS SLOW AS IT ONCE WAS!!

Attached a few photos of my (customized) Samebike JG20, simple 'Saxin' handle bar control unit and the main controller.

I'd LOVE to hear from other owners of this JG20 (or its similar Samebike derivates). I want to know about their experiences, about anything to make this freaky '6 speed pedal, 1 speed motor' pedelec a little more useful!

Thanks so much for reading this far!
And pardon my 'German English'; I tried my very best to keep it entertaining AND informative at once. Whoever finds spelling errors may keep them - for free!

Thats a lot of info, some of which goes well over my head.
There are plenty of controllers on ebay, that would appear to be a better fit for you. Ones with an LCD dispplay, often allow programming things on the display. Make sure you get the instructions before buying!
You could try removing every second magnet on the PAS sensor disk and see what that does, good or bad.
You can select on some LCD type controllers, a different wheel size, as smaller wheel sizes should make your bike faster.
The problem of having to pedal fast is well known, but I found some replacement rear gear cassettes, for a Shimano gear change, that had smaller sprockets, e.g. less teeth, which slowed down my pedaling about 10%, but not from Shimano, but quality wise, appeared to be slightly better, as the chain never ever dropped off again!! Or I aligned it better than the factory, who knows?
The reason that some bikes have the motor and gearing in the crank area, is to fix the same problem with fast pedaling. But some have plastic gears, Bosch for example, UGH!
Also, a larger crank gear will also slow down the pedaling for the same road speed.
Ebay should have all the items you might need.
I hope that some of these "meanderings" of mine, help you a little bit more.....
Generally, e-biking is really great, I am on my second cheapo (the first one lasted over 6 years and the battery was still good, all bought secondhand!!) and I am still very happy...
regards
Andy

 

[Craigs]

I think the most likely possibility is that the cells in the battery were out of balance when you first received it, resulting in it having low voltage so both slower and weaker performing,

At each charge the battery's own internal BMS* takes the battery to full charge and then balances the cells, probably failing to fully achieve that in the first two charges but finally achieving it with the third.

Then with both full voltage and capacity, the bike was able to reach the design speed and performance. You'd need to add a throttle to be able to have lower speeds, perhaps someone with knowledge of that controller could advise if that is possible.

*BMS = Battery Management System.
.

Cool idea!!
YES, that sounds rather reasonable, thank you! Nobody brought this up in the German forum.
I do not know much about "BMS" (must study!), but understand that packs of batteries must be 'in sync' to operate efficiently.
Maybe my cheap controller does a 'run-in' like balance load control after all; and I was right all the time?

The BMS theory raises a few questions:
1) Can I re-invoke this mode somehow, without damaging the battery pack, the motor or the six power transistors? How?
2) Wouid the unbalanced battery pack deliver full capacity at a LOWER power output level as it did for me? Would such a pack have the full voltage of 36V, as visible on the 'voltage' LEDs on the flimsy Saxin display? Three steps is coarse, the upper LED disappeared around 27km in the 'broken' mode, now around 20km due to the higher power output.

As said, I am a newbie, trying to learn, looking for other owners of these odd Chine thingies.

I did not expect much, did not pay a lot (ca. US$450), was quite pleased in its presumed 'defective' state. And do not want to dump money and parts into this JG20, not knowing how long it may last.

Thanks for any clarification and idea, especially about the mentioned controller and totally obscure 'Saxin' handgrip!

 

[Craigs]

@Andy: thanks for your various thoughts!

To clarify: the bike has RWD, the black box under the crank contains the controller.
PAS is actually a nuisance on this bike: it overrides any (lower) handle grip setting and will push the speed up to the new limit anyways. That's why I decided to remove PAS sensing altogether. Now I can pedal at 5...25km/h WITH motor support, holding the grip in place..
As hard as it is to believe; it seems to be a SINGLE power output design (in pedal assist mode), aimed at 25km/h resp US: 20mph, by design. Rather unusual, no?

With 46teeth:14-28teeth and 20" wheels there is little room left for extending the 6spd gear ratio. It would be costly, and the limited battery range issue would remain anyways.
Changing the handle controls alone would probably NOT solve the issue, unless someone can confirm that my controller -AA004 is supporting power stepping like version -AA006 on other bike models with a LCD and powerstep display.

 

[Andy-Mat]

@Andy: thanks for your various thoughts!

To clarify: the bike has RWD, the black box under the crank contains the controller.
PAS is actually a nuisance on this bike: it overrides any (lower) handle grip setting and will push the speed up to the new limit anyways. That's why I decided to remove PAS sensing altogether. Now I can pedal at 5...25km/h WITH motor support, holding the grip in place..
As hard as it is to believe; it seems to be a SINGLE power output design (in pedal assist mode), aimed at 25km/h resp US: 20mph, by design. Rather unusual, no?

With 46teeth:14-28teeth and 20" wheels there is little room left for extending the 6spd gear ratio. It would be costly, and the limited battery range issue would remain anyways.
Changing the handle controls alone would probably NOT solve the issue, unless someone can confirm that my controller -AA004 is supporting power stepping like version -AA006 on other bike models with a LCD and powerstep display.

Lowering the needed pedal speed with gearing improvements, would usually save some power, as you can "keep up" better....the parts are not expensive. I have a top gear with 11 teeth at the rear on my previous bike, and 46 on the crank. I was going to change the crank and then I bought a new cheapo bike....I have been most happy with it, but some others have had problems....
I am heavily into DIY, which allows me to have a cheapo bike!!
Your controller sounds terrible.....
Maybe invest in a new bike, as e-bikes are really great, I have been an e-biker for over 8 years and I will be 73 this year. It keeps me fit!
regards
Andy

 

[Craigs]

Chapeau, Andy!
But IMHO foldable bikes are not really made for speeds above 20km/h. Even back in the 1970s when they became popular. 'Duomatic' was their biggest feature, a simple 2 speed hub.

Even if I change the overall ratio of the gearset I'd still feel rather unsafe on this el-cheapo pedelec. The disk brakes are rather soft (need to tighten all after 200km or so), the front fork is 'so lala'. It IS great for field trips around my area, for shopping during the summer. It easily fits into my car's trunk, one of the reasons I opted for this 'old school' design, with a practical and sturdy rack in the rear.
I was quite pleased on my first trips (50km non-stop on a 20" foldable bike IS an adventure, trust me!). Power assist DOES work neatly, a great improvement in hilly areas like mine. One can feel the extra punch, especially if removing the drive for a moment.

Just this stupid self-tuning to Vmax=25km/h is still nagging me. If there is any trick to reset the controller to the original 'slo mo' mode with lower power output, I'd be 'happy as a clam' as you would say.
Or if I could get my hands on a complete set for the Samebike XMZ1214. A bike with too tiny wheels and a too large battery - but with a reasonable 'multi power' control and LCD unit with extra features.
I guess that's 'life' - you get what you pay for..

 

[flecc]

Maybe my cheap controller does a 'run-in' like balance load control after all; and I was right all the time?

That wouldn't happen by design and the controller has no effect on balancing, which is solely the domain of the BMS. The BMS uses a tiny bit of battery power to run and on cheap ones it's on all the time and is often taken from one end cell, so this can result in that being low in voltage and lowering the overall voltage slightly.

It's difficult to comment on your other questions since there are so many variables. For example, the fact you were able to pedal a bit when it was slower means you were helping out so extending the range. Now the pedal cadence is too high you probably aren't helping much, if at all.

If you have an accurate multimeter, the battery voltage fully charged should be 42 volts. That declines during riding to about 32 volts at the cutout setting.
.

 

[tonyw]

From reading the symptoms, my thought was that maybe there is a loose connection somewhere which has reconnected itself. It occurs to me that if there is a setting (jumper?) to set wheel size, then if it was set to a larger size the controller might think the bike is going faster than it is, and reduce performance?

 

[picusiaubas]

I have seen a lot of reviews where people reported that the speed magically increased for this Samebike. Check for example reviews on this Gearbest listing: https://www.gearbest.com/electric-bikes/pp_009273919376.html?wid=1433363

I found a way to unlock speed limit for Samebike XMZ1214 here: https://www.pedelecs.co.uk/forum/threads/remove-speed-from-samebike-20lvdx30.33574/page-2#post-490351 . You can get the speed limit back by doing similar actions. Check post #26.

P.S. Greetings to David Hou, he has neither responded to me when I asked for a possibility to buy a new controller. I also tried the "European" distributor at http://samebike.nl , but they don't seem to be any better at responding

 

[vfr400]

I have seen a lot of reviews where people reported that the speed magically increased for this Samebike. Check for example reviews on this Gearbest listing: https://www.gearbest.com/electric-bikes/pp_009273919376.html?wid=1433363

I found a way to unlock speed limit for Samebike XMZ1214 here: https://www.pedelecs.co.uk/forum/threads/remove-speed-from-samebike-20lvdx30.33574/page-2#post-490351 . You can get the speed limit back by doing similar actions. Check post #26.

P.S. Greetings to David Hou, he has neither responded to me when I asked for a possibility to buy a new controller. I also tried the "European" distributor at http://samebike.nl , but they don't seem to be any better at responding

That's to release the 25km/h speed limit.

What exactly are the 5 LEDs on the throttle for? What makes them light up or go out?

 

[Wicky]

Can't you just ride it with minimum assist level at 20km/h to regain your range...

 

[picusiaubas]

That's to release the 25km/h speed limit.

Yes, but very similar trick worked to get the limit back. Just used other brake and keep throttle pressed.

 

[Craigs]

Can't you just ride it with minimum assist level at 20km/h to regain your range...

Sorry for the late response (I was too busy riding and fiddling..):
No, that does not work, as the bike only knows ONE power setting (FULL) and only one mode (kick power in whenever pedals are mov ing). So it will always push to 25km/h when pedaling.
See my final 'exam' below for details.

 

[sjpt]

Certainly sounds like some hairy bike in its current setup, and potentially pretty dangerous (for you and for others). It shows two difficulties.

(1) Engineering: How confusing the engineering of compatible parts is to make it really confusing as to what alternative controller might work.

(2) Legal: how difficult it is to phrase sensible laws. It sounds as if it does fall withing the letter of the law, whereas lots of bikes with almost identical motors but proper controls do not just because they happen to have 350 stamped on the motor rather than 350.

Have you tried things like long presses on whatever buttons you do have to see if you magically hit some settings menu? Sounds as if there is only one button, or even just the key? Can you somehow rig friction against the throttle so it stays put?

 

[Craigs]

Sorry, I have not updated this topic for a while, was too busy fiddling and riding...

Here is how I solved my issue with this ONE-POWER-MODE controller, as I could not reset it to the factory mode of Vmax=20km/h:

As the PAS would always trigger the full power mode whenever pedaling I made it optional, adding a switch to the handle bar. This way I can disengage the PAS and control the electric power manually at will and ANY level, using the handle bar gas grip.
Meaning I can adjust the power output for any desired speed up to Vmax, but have to hold the gas grip, like on a motorcycle, while pedaling along.
Range of the 288Wh pack is now back to 55-60km for a single charge (from around 40km with PAS active), around 5Wh/km, cool! I did some very nice trips with the modified bike, at avg speed of 20km/h, perfect for the 20inch wheels and high cadence gearing.

I also invested into a GTC power meter to watch over power output, true battery voltage, power consumption etc. It allows to see the actual wattage, the accumulated Wh consumed, the battery voltage and amps under load etc.
The cheap meter (which is usually bought and installed for solar panel monitoring) is very accurate (home bench testing) and very useful for this bike with its anemic 3LED power display.

But I found a few very surprising facts when observing the readings during my rides:
- a 36V battery really has around 42V when fully charged, so it contains TEN elements of 4.2V?
- even during regular rides the battery operates way above 36V
- under load the battery on this 250W bike is drained with up to 13Amps, around 480W!
Why a 250W bike will operate at almost twice the power (at regular speeds below 25km/h) I cannot explain, but it is a fact for my JG20. Does the full power get to the motor, or is it partly consumed by the controller FETs? Cannot say.

Also interesting is the significant voltage drop of the battery under load, a typical effect of these Li ion packs: at full throttle and power the voltage may drop from 39V to 36V or lower, recovering quickly when the load is released.
This behavior is very unfortunate for folks like me who live on TOP of a steep hill. After a trip the battery may be down to 35V already, still containing 'juice' for another 10km or so. But a steep hill climb will squeeze the voltage below the shut off trigger point (around 33V?) and will NOT allow to restart the motor afterwards, bummer. I ended up pushing the bike uphill more than once..

The season is over; I rode about 550km with this weird Samebike JG20. It IS fun and WAS cheap, it DOES work, but needed the special TLC and mods to become a useful vehicle.
Would I buy it again? Not with the simple and poor controller and display it uses, not with the bad gearing ratio of the Shimano set.
A conversion of all controller electronics or the Shimano sprocket sets would cost more than the bike is probably worth.
My own solution set me back by 7Euro for the PAS shut-off switch and the GTC power meter - well spent!

Thanks for reading and your suggestions; I learned a lot about pedelecs this year!