Just had first wreck, unexpected shutdown on 14C

[fourthewin]

Thankfully, I didn't break anything and for the most part I'm very lucky, just nicked up. It trashed the trolley handle and put some big scraps in it even through the bumper tape.

I really don't know what happened guys....I was cruising at about 13-14mph and got behind some bikers. They moved out of the way and I went to pass them going up a slight hill, and accelerated to about 16mph. I wasn't going super fast, I wasn't powering up the hill hard, and the bastard just cut-off and dumped me. I had been monitoring my battery as I was getting close to the 50% mark but it hadn't dipped to to 50% or below yet. I wanted to go easy and run the battery down to around 20% for battery maintenance. 

I thought the Kingsongs specifically were designed to not do this. It's kind of scary if it just randomly cuts off like that. 

Any ideas to the cause? I was able to get back home in one piece and it ran ok the rest of the way back but I was going pretty slow. 

Here's some photos: 

 

 

[Hunka Hunka Burning Love]

How much do you weigh, how long were you climbing and how steep of a hill was it?  What tire PSI and what battery watt hour size are you running?  Was it pretty cold outside?  Even though you had 50% battery, going up a hill can tax the wheel by drawing extra current to keep you going as the load demand is higher on the motor while trying yo maintain the same speed.  58 volts seems a little on the low side as aren't these packs supposed to be at 67.2V?

The safe cruising speed on level ground can be different than the safe cruising speed going up an incline.  Also I hear that the KS14's can overheat clmbing hills (@Cloud where ya be man?) so you have to be careful of a shutdown.  If you have a good phone case, you can try monitoring the battery level indicator as you go uphill to see where it drops down to.

I try to imagine the battery level sort of like a rubber band.  It varies when you're riding and on how much demand you place on the motor in terms of acceleration and climbing.  A measurement while stationary doesn't factor in the draw on the battery as compared to rolling around or up a hill.  Try to imagine a tungsten filament light bulb attached to a battery.  It glows at a certain brightness when turned on.  Now imagine attaching 10 more light bulbs to the same battery and see how bright it shines.  Now imagine if the battery is at 50% charge.  How bright will the 10 bulbs shine as compared to one bulb?  At some point of adding bulbs they may not light at all.  Not exactly a perfect analogy, but it kind of makes sense.  I'm sure @esaj has a better one up his sleeve.    Hold on a sec... deja vu!

Any wheel can cut out like that if it overheats or the current demand exceeds what the battery can deliver resulting in the BMS triggering a shutdown of the voltage being supplied.  A weak cell or cells in the pack can also create unexpected results.  Some wheels might give you a warning like a beep or tiltback if there is time, but sometimes depending on the battery level and condition, things happen pretty rapidly.  Triggering a tiltback might even push the battery too much as the wheel has to give a burst of speed so it could trigger the BMS during the process.  It's sort of like blowing a fuse when you add one too many hair dryers to one socket.... or at least that's my interpretation of the process.  I'm no expert so this is just what I theorize is happening.

[abinder3]

14 minutes ago, Hunka Hunka Burning Love said:

How much do you weigh and how steep of a hill was it?  What tire PSI and what battery watt hour size are you running?  Was it pretty cold outside?  Even though you had 50% battery, going up a hill can tax the wheel by drawing extra current to keep you going as the load demand is higher on the motor.  The safe cruising speed on level ground can be different than the safe cruising speed going up an incline.  Also I hear that the KS14's can overheat clmbing hills (@Cloud where ya be man?) so you have ot be careful of a shutdown.  If you have a good phone case, you can try monitoring the battery level indicator as you go uphill to see where it drops down to.

I try to imagine the battery level sort of like a rubber band.  It varies when you're riding and on how much demand you place on the motor in terms of acceleration and climbing.  A measurement while stationary doesn't factor in the draw on the battery as compared to rolling around or up a hill.  Try to imagine a tungsten filament light bulb attached to a battery.  It glows at a certain brightness when turned on.  Now imagine attaching 10 more light bulbs to the same battery and see how bright it shines.  Now imagine if the battery is at 50% charge.  How bright will the 10 bulbs shine as compared to one bulb?  At some point of adding bulbs they may not light at all.  Not exactly a perfect analogy, but it kind of makes sense.  I'm sure @esaj has a better one up his sleeve.  

Agreed.
KS14s will overheat going up too steep of a hill and just shut down.

OP; was there any beeping while going up the hill?

Allen

[fourthewin]

@Hunka Hunka Burning Love Thank you for a detailed response. 

Let's see if I can answer your questions. 

1. If using this chart it's probably a 12.5% "grade" (don't be confused with the blue degree lines)
2. I am 200lbs. 
3. I run at 50psi on the tire
4. It's roughly 70 degrees outside and the sun was setting. I was wearing a pullover which protected me a bit. 
5. This one has the 680whr battery

[abinder3]

The King Song 14D has a max speed of about 17mph (according to the King Song web site).

I don't know what the max speed of the 14C is though.

Have you ever encountered 'tilt back'?  If you haven't, maybe you mistook the 'tilt back' for shutting down.  Some people do get confused with the 'tilt back' and think it's shutting down on them.

(just some thoughts.)

 

Allen

[fourthewin]

8 minutes ago, abinder3 said:

Agreed.
KS14s will overheat going up too steep of a hill and just shut down.

OP; was there any beeping while going up the hill?

Allen

That's the thing....NONE! While I hit the beeping a lot when cruising (Speed limit is set to 26mph, 27, 28, 29), there was ZERO going up this, I simply wasn't going fast enough! 

[fourthewin]

2 minutes ago, abinder3 said:

The King Song 14D has a max speed of about 17mph (according to the King Song web site).

I don't know what the max speed of the 14C is though.

Have you ever encountered 'tilt back'?  If you haven't, maybe you mistook the 'tilt back' for shutting down.  Some people do get confused with the 'tilt back' and think it's shutting down on them.

(just some thoughts.)

 

Allen

Oh yes, but this was a full blown shut-off. I knew what happened the second my foot hit the ground and went into damage control. Lol

[abinder3]

Just did some searching on the internet and supposedly, the 14C has a max speed of about 15mph.  You stated that you think you were going 16mph uphill.  Sounds like you may of encountered 'tilt back' or it shut down because you were pushing it too hard.

(again, just a thought)

 

Allen

[abinder3]

Just now, fourthewin said:

Oh yes, but this was a full blown shut-off. I knew what happened the second my foot hit the ground and went into damage control. Lol

You may of tried to accelerate too hard going up a hill at 50% battery.
(and again, just a thought)

 

Allen

[fourthewin]

5 minutes ago, abinder3 said:

Just did some searching on the internet and supposedly, the 14C has a max speed of about 15mph.  You stated that you think you were going 16mph uphill.  Sounds like you may of encountered 'tilt back' or it shut down because you were pushing it too hard.

(again, just a thought)

 

Allen

Not sure where you are getting getting your information. Kingsong's own marketing material shows 30kph (18.6mph). See here. Additionally, ewheels shows it as 19mph. See here. 

[abinder3]

1 minute ago, fourthewin said:

Not sure where you are getting getting your information. Kingsong's own marketing material shows 30kph (18.6mph). See here. Additionally, ewheels shows it as 19mph. See here. 

The 14C here:
https://www.wheelers-store.com/en/product/king-song-14c/

 

The 14D here:
http://www.kingsong.com/upload/file/contents/2016/12/5858f66961eca.pdf

 

[abinder3]

4 minutes ago, fourthewin said:

Not sure where you are getting getting your information. Kingsong's own marketing material shows 30kph (18.6mph). See here. Additionally, ewheels shows it as 19mph. See here. 

Your like says "around 30kph".

[Hunka Hunka Burning Love]

12.5% grade is fairly steep.  @Tilmann where is that Rockwheel hill climbing video at that abandoned German military base showing the different grades?

Also going downhill can be perilous... 

 

[fourthewin]

4 minutes ago, abinder3 said:

The 14C here:
https://www.wheelers-store.com/en/product/king-song-14c/

 

The 14D here:
http://www.kingsong.com/upload/file/contents/2016/12/5858f66961eca.pdf

 

Neither of these are the official kingsong website which is www.szkingsong.com. 

Thanks for the info though. 

4 minutes ago, Hunka Hunka Burning Love said:

12.5% grade is fairly steep.  @Tilmann where is that Rockwheel hill climbing video at that abandoned German military base showing the different grades?

Also going downhill can be perilous... 

 

I'll take some more photos tomorrow. I could be wrong, but I don't think it's very steep. 

[abinder3]

2 minutes ago, fourthewin said:

Neither of these are the official kingsong website which is www.szkingsong.com. 

Thanks for the info though. 

I'll take some more photos tomorrow. I could be wrong, but I don't think it's very steep. 

Ummm............ Yes, the first one is an official King Song web site.

[Hunka Hunka Burning Love]

I think this is a 13% grade:

https://humofthecity.com/2012/02/04/san-francisco-hills-and-grades/

Keep in mind some of these rated speeds are for a certain rider weight and might be maximum speeds at which failure occurs instead of what a "safe" riding speed is rated at.  For example, my Ninebot has maximum speed I believe of 30 KPH.  I can safely cruise on a flat road at about 22 KPH when tiltback occurs so I have about 8 KPH spare speed just in case I shoot past that 22 KPH for whatever reason (fast acceleration, downhill, gust of wind on my back).  I do not expect to be able to hit 30 KPH safely as torque reaches zero at that point so it cannot balance me any further.

If I were 200 or 110 pounds instead of 167 pounds in weight, I'd expect the performance of the wheel to vary a bit as the load on the battery and motor would be different.  For example If I was 400 pounds I don't think my Ninebot could move me safely at 22 KPH... Riding these wheels is a multi-factored equation where lots of variables come into play.

[fourthewin]

4 minutes ago, abinder3 said:

Ummm............ Yes, the first one is an official King Song web site.

*facepalm*. Ok. Thanks. 

[abinder3]

5 minutes ago, fourthewin said:

*facepalm*. Ok. Thanks. 

Sorry, I meant the 2nd one.
(If you look under the "Contact" page, you will see that it is.)

 

Allen

[Hunka Hunka Burning Love]

One experiment to try is to get on a wheelbarrow and while sitting directly over the wheel, have someone roll you around on flat ground.  Head towards a 12.5% hill and see how much energy it takes for that same person pushing you to move you uphill at the same speed or while trying to accelerate.  Moving 200 pounds of rider around isn't too bad on flat ground, but going uphlll will be a way different story!  That may be why some newer Kingsong firmware tends to cut performance at lower than 50% battery levels.  Unless you have a mega watt hour pack, the draw up some hills could be too much for the wheel and components.  They could be trying to avoid this exact situation that fourthewin experienced.

EDIT:  Ohh  found it...

 

[meepmeepmayer]

Sounds like a shutdown due to too much power demand? Do the Kingsongs have a 80% (or so) warning? Though I can see a bump/obstacle being enough for going from below 80% to over 100% in an instant.

Also, never believe manufacturer or dealer speed declarations (even ewheels is exaggerating some numbers, e.g. ACM top speed). The safe speed is the speed where the default ( and unlocked for KS) alarm beeps start.

Well, lucky you didn't get hurt. Yellow wheel looks really nice btw

edit: a neat idea may be, look at the used power (W) when going at speed limits (1st and 2nd beep) while on flat ground. Then, compare that wattage to going uphill, possibly slower. Not sure if you get helpful results, but it's an idea. Unless someone tells us this won't give anything useful, I plan to do that too.

[Jrkline "Wheel Whisperer"]

59 minutes ago, meepmeepmayer said:

 

Sounds like a shutdown due to too much power demand?

 

I think you hit it on the head.I have 2 14c's along with the 16b and 18a.16mph is near the top speed for these wheels and if you factor in 200lbs. plus a grade and less than 50% battery plus high internal temp then the wheel is at or very close to its max available power.And if the app voltage shown in your pic is accurate,58v is about 30-35% battery power,not 49%.Usually 60v is right around 50% battery.(I have installed the digital led voltmeter mod on several of my wheels to more accurately judge battery levels.And all of them are at about 50% battery when the led reads 60v whether its a Gotway,Kingsong or IPS wheel).

 

 

 

 

 

 

 

 

[Tilmann]

2 hours ago, Hunka Hunka Burning Love said:

12.5% grade is fairly steep.  @Tilmann where is that Rockwheel hill climbing video at that abandoned German military base showing the different grades?

Also going downhill can be perilous... 

 

@Hunka Hunka Burning Love here'ya go:

 

[esaj]

9 hours ago, Hunka Hunka Burning Love said:

I try to imagine the battery level sort of like a rubber band.  It varies when you're riding and on how much demand you place on the motor in terms of acceleration and climbing.  A measurement while stationary doesn't factor in the draw on the battery as compared to rolling around or up a hill.  Try to imagine a tungsten filament light bulb attached to a battery.  It glows at a certain brightness when turned on.  Now imagine attaching 10 more light bulbs to the same battery and see how bright it shines.  Now imagine if the battery is at 50% charge.  How bright will the 10 bulbs shine as compared to one bulb?  At some point of adding bulbs they may not light at all.  Not exactly a perfect analogy, but it kind of makes sense.  I'm sure @esaj has a better one up his sleeve.    Hold on a sec... deja vu!

Any wheel can cut out like that if it overheats or the current demand exceeds what the battery can deliver resulting in the BMS triggering a shutdown of the voltage being supplied.  A weak cell or cells in the pack can also create unexpected results.  Some wheels might give you a warning like a beep or tiltback if there is time, but sometimes depending on the battery level and condition, things happen pretty rapidly.  Triggering a tiltback might even push the battery too much as the wheel has to give a burst of speed so it could trigger the BMS during the process.  It's sort of like blowing a fuse when you add one too many hair dryers to one socket.... or at least that's my interpretation of the process.  I'm no expert so this is just what I theorize is happening.

The rubber-band analogy (at least sort of) works, the battery voltage will be going up and down depending on power demand, ie. riding flat / accelerating / climbing hill / braking, and "stretches" further (especially downwards) the more empty the battery is. More light-bulbs, well.. you would see them shining less bright the more you add, but it's not exactly what happens with the battery when riding.

The two typical reasons for a BMS-cutout during discharge are either the voltage dropping too low (low voltage protection) or too high current demand (short circuiting protection). The first one is meant to prevent overdischarging the pack and damaging the cells, the latter to keep the discharge current at safe values as well as protect the battery from short-circuit. With too high current, the BMSs typically seem to "reset" after the load is removed (like a short circuit), but with the overvoltage protection, many BMSs have "latching" action, where the BMS won't start giving out any current until the battery voltage has risen enough. Since the "release"-voltage can be much higher than the triggering voltage, in many cases the battery won't start "working" again until put on charger.

I've used this image a gazillion times, it's a graph drawn from a recording I took from Vee's MCM2s, getting going from standstill on level ground and then climbing up a short 15 or 20 degree steep hill (26-36% in slope grade), don't remember which it was, with a slight slope downwards after the crest. Right-hand scale is for the power-graph, rest use the left-hand scale. Do note that I'm lightweight though, 130lbs or less with full gear (<60kg):

No cutouts happened here, and even the current and power-numbers are doubtful (it is said at least the older Gotway's telemetry-data exaggerates the current, and the power is simply calculated as voltage * current in the above graph), especially since the voltage is not from the motor back-EMF but the battery (like it is in all wheels), so you won't get real motor output power from that.

Anyway, what can be easily seen from the graph is the large power demand the climbing causes, and the voltage to drop with high current (and slight rise in temperature over the entire period). The first current spike on the left is just getting going, to get the motor turning from standstill (at level ground, the actual climb won't start until maybe somewhere between 6-8 seconds in the graph). The battery voltage doesn't sag that much, just judging from the graph (I have the original recording... somewhere in my old machine), it drops from around 61-62V at rest to around 58V during the climb, but with a heavier rider, more discharged pack and/or higher current, the drops would probably be much larger, and could potentially go low enough to trigger the BMS protections (assuming it has any ). The slightly negative current is slight regenerative braking (going over the crest of the hill and coming down a small slope on the other side).

 

Another graph of riding down the street and testing "power braking":

You can see the battery voltage bouncing up a bit during the braking, regeneration going on. With more empty batteries or heavier rider, both graphs would show much larger swings in the voltage.

 

 

Quote

edit: a neat idea may be, look at the used power (W) when going at speed limits (1st and 2nd beep) while on flat ground. Then, compare that wattage to going uphill, possibly slower. Not sure if you get helpful results, but it's an idea. Unless someone tells us this won't give anything useful, I plan to do that too.

At least as long as you compare the results taken from the same measurement device (in this case, the wheel itself ), in very similar conditions, you can get comparative results. So even if you can't trust the absolute wattage etc. numbers being exactly correct, at least you can compare the required climbing power vs. flat speeds...

[Christoph Zens]

So the assumption is that it was a BMS shutdown? If that's true, then I would say the motor controller is not working properly.

The firmware has to know what the systems hardware limitations are, and must not exceed them under any circumstances. Why on earth would the firmware decide to overload the power supply and cause a complete and sudden loss of power with the rider definitely flying off the wheel, instead of just letting the wheel lag behind while pumping all AVAILABLE power to the motor to keep up as much as possible? This would cause the rider to tilt forward as the wheel under his feet lags behind, but it would at least give him a chance to react and ride it out.

If there is no more power to be had, it's no use to stick to the simple control loop and overload the system up to a complete failure. Controller software needs to allow for errors in wheel balance,  in favor of staying within the safe operating area of all its components. Battery voltage and current is constantly monitored. It should be no problem to limit motor power output when battery voltage drops too low or currents are too high, approaching BMS limits. 

Under normal situations, it is of course better to warn the rider upfront by doing the opposite, which is to drive the motor even harder to overtake the rider and cause the pedals to tilt back, since this will safely slow him down. But if things got bad all of a sudden, there is no more power reserve for tilt back, and no time for beeping, any wheel should keep going at maximum permissible power output and hope for the rider to correct his balance.

Exceeding BMS limits is a software error and must be fixed. There is no excuse for this behavior and I don't see how a sudden power loss due to the BMS shutting down could be preferable to any other option. 

Also, overheating is no reason for a sudden shutdown. I used my NB1 at 35 Celsius outside temperature climbing a steep hill in the woods until the overheat warning kicked in at 70C system temperature. The wheel did not shut down on me while I was riding. Just started beeping and kept going until I stepped off to let it cool down. That's correct behavior. Same thing with trying to climb faster than the wheel can handle. On a very steep hill I climb almost every day, I can go like 7-8kph. Pushing it harder causes it to beep as it approaches its 1.5kW power limit. So the beeps we can configure as a speed warning are one thing, but any wheel should beep by itself regardless of current speed, when power output approaches critical values.

The only problem with these warnings may be that there is no time, when a rider causes the system load to change too fast. I for myself see riding the EUC as doing SMALL adjustments to a delicate control loop. Any control loop has a certain feedback delay and needs time to adjust its output to the new situation. So even when accelerating to overtake someone, take it easy, and pay close attention to the wheels response. Ultimately, it is the riders responsibility to stay on top of the wheel, and not the wheels responsibility to always stay exactly below the rider. That's how I see it and how I ride the relatively weak NB1 for almost 2000km now, without any crashes. 

[DaveThomasPilot]

21 hours ago, Hunka Hunka Burning Love said:

 

Any wheel can cut out like that if it overheats ...

Nothing should overheat quickly--the batteries, ESC, and motor all have a lot of thermal mass.

Doesn't the wheel start doing a tilt back as the temperature gets high before cutting out completely?  If not, why not?