KS-16 680Wh Jittery Ride

[ninebot156]

Guys

Just got a King Song 16" 680Wh last weekend.

Noticed a weird behavior, which I managed to replicate.

 

1) When the wheel is fully charged, the wheel feels jittery. The feeling is like as if the power is momentarily cut for a split second.
Luckily, no falls so far. But the ride is less comfortable that my old Ninebot E+

 

2) when the wheels reached 7km mark after a charge, the KS becomes buttery smooth. Better than Ninebot. It really glides.
No issues for the next 40-50km. Just pure joy.

 

3) Wonder if anyone else has the jittery feeling only when the battery is fully charged up?

[HEC]

Well I hardly ever use the KS-16 fully charged but if I do I've not noticed anything like that. Are you driving down the hill at the start? Are you disconnecting charger right away after it changes to green? What battery voltage the mobile app shows after full charge and then again after those 7 Km of ride when this effect disappears?

[Chriull]

Maybe your charger puts out a voltage at the upper range? Maybe a bit above the 67.2V ? Do you have a voltmeter to measure the charger voltage?

[esaj]

Overcharge due to regenerative braking was also what came into my mind, but "proper" BMS shouldn't cut out due to overcharge through the discharge-side (regenerative braking).

5 minutes ago, Chriull said:

Maybe your charger puts out a voltage at the upper range? Maybe a bit above the 67.2V ? Do you have a voltmeter to measure the charger voltage?

I was checking the 5A charger of my friends' KS16 earlier, and it occurred to me, that since the BMS has reverse polarity protection diodes, shouldn't the voltage actually be something like 67.7-67.9V to overcome the voltage drop of the diodes if one wants to fill the batteries "to the brim"? Not that it's very useful to force them into as high as possible voltage, as the last volt or half a volt probably won't bring much capacity-wise, but only stresses the cells  (assuming that the balancing already starts at lower voltages).

[Neale Gray]

This is a clear hardware fault, motor replacement required to rectify.

[HEC]

5 minutes ago, esaj said:

I was checking the 5A charger of my friends' KS16 earlier, and it occurred to me, that since the BMS has reverse polarity protection diodes, shouldn't the voltage actually be something like 67.7-67.9V to overcome the voltage drop of the diodes if one wants to fill the batteries "to the brim"? Not that it's very useful to force them into as high as possible voltage, as the last volt or half a volt probably won't bring much capacity-wise, but only stresses the cells  (assuming that the balancing already starts at lower voltages).

I was thinking the same - basically there should be difference in voltage in chargers for wheels with and without the protection diodes. Technically "intelligent" charger should be able to detect that itself and adjust output voltage accordingly, otherwise switch on the (moded) charger can be used to choose between 67.2 and 67.9V ... Alternatively set it to 67.9 - 68V and use Charge Doctor  As I have apart of the 5A charger from @Jason McNeil also a "generic" 2A charger for the wheel without protection diode I might open that one and up the voltage a bit so once a while I can top KS-16 fully to assure proper balancing as well although I'm pretty sure it's already balancing from about 66.4V (4.15V per cell) to which I have my Charge Doctor cut of voltage set at the moment (though as there is a diode it's probably resulting in only 63.9-ish V anyway - it shows 87% capacity after charge, would need to re-check the voltage shown in the app). On other hand I feel that that's the safe voltage to not overstrain the cells on regular chargers as I actually think that the 64.8V option on the 5A fast charger from @Jason McNeil is a little bit too low though still better than full charge if you don't have charge doctor. The "disadvantage" of using the switch is that it will charge much slower towards the end and will not cut the current after reaching the set voltage so CD is still worth purchasing (especially since Chris now added new options in latest version).

[Chriull]

5 minutes ago, esaj said:

Overcharge due to regenerative braking was also what came into my mind, but "proper" BMS shouldn't cut out due to overcharge through the discharge-side (regenerative braking).

Yes - it should not cut out, but with too much battery voltage maybe the firmware can't really break anymore and by that create the jittery feeling for the first 7km?

Maybe its also the "capacitor leg" problem from the KS16, but imho it should not, since the KS drives normal after the first 7km... But it should not hurt to check it?

5 minutes ago, esaj said:

I was checking the 5A charger of my friends' KS16 earlier, and it occurred to me, that since the BMS has reverse polarity protection diodes, shouldn't the voltage actually be something like 67.7-67.9V to overcome the voltage drop of the diodes if one wants to fill the batteries "to the brim"? Not that it's very useful to force them into as high as possible voltage, as the last volt or half a volt probably won't bring much capacity-wise, but only stresses the cells  (assuming that the balancing already starts at lower voltages).

This voltage drop should be measured and verified before one tries to charge the battery packs upt to the brim! There seem to be quite some differences. For example the ks16 delivered from @1RadWerkstattuse according to chris a mosfet as reverse polarity diode and only have a very low voltage drop (imho something about ~0.3 - 0.4V). And this reverse polarity "diode" is just in the first pack from the charger - the second one has none.

other wheels could have a reverse polarity diode in each pack in a series configuration, so only the first pack could be fully charged and the following have a bit less... And if one measures in such a case the voltage drop over all the packs and adjusts the charger output voltage accordingly one would overcharge the first pack!

12 minutes ago, Neale Gray said:

This is a clear hardware fault, motor replacement required to rectify.

Could also be - but strange that it only occurs at the beginning with fully charged batterries!?

anyhow - @ninebot156should be carefull driving his KS16 untilthis issue is resolved!

Measuring the charger output voltage should not hurt and since the wheel is brand new contacting the resseller should be a valid choice!

[HEC]

7 minutes ago, Chriull said:

This voltage drop should be measured and verified before one tries to charge the battery packs upt to the brim! There seem to be quite some differences. For example the ks16 delivered from @1RadWerkstattuse according to chris a mosfet as reverse polarity diode and only have a very low voltage drop (imho something about ~0.3 - 0.4V). And this reverse polarity "diode" is just in the first pack from the charger - the second one has none.

other wheels could have a reverse polarity diode in each pack in a series configuration, so only the first pack could be fully charged and the following have a bit less... And if one measures in such a case the voltage drop over all the packs and adjusts the charger output voltage accordingly one would overcharge the first pack!

I'm not sure I fully understand what you mean? Multiply battery packs each with own BMS are connected in parallel not serial so charging voltage will be same on all and only difference on protection diode or MOSFET would be minimal due to the tolerances between each diode or MOSFET. There is no way that it would happen as you describe it ...

[Chriull]

4 minutes ago, HEC said:

I'm not sure I fully understand what you mean? Multiply battery packs each with own BMS are connected in parallel not serial so charging voltage will be same on all and only difference on protection diode or MOSFET would be minimal due to the tolerances between each diode or MOSFET. There is no way that it would happen as you describe it ...

Yes - battery packs are always in parallel. But for some wheels (ks and gotway with bigger capacities imho) they are in a cascade - the discharge output of the first pack goes to the charge input of the second and so on... So they are one after another like in a series. But you are right, series connection would mean someting different and the word cascade should be used instead. For this cascade connection each pack with a protection diode gets less voltage than the pack before... (If it is not made like at @1RadWerkstatt's packs where there is no protection diode but only in the first pack)

[HEC]

5 minutes ago, Chriull said:

Yes - battery packs are always in parallel. But for some wheels (ks and gotway with bigger capacities imho) they are in a cascade - the discharge output of the first pack goes to the charge input of the second and so on... So they are one after another like in a series. But you are right, series connection would mean someting different and the word cascade should be used instead. For this cascade connection each pack with a protection diode gets less voltage than the pack before... (If it is not made like at @1RadWerkstatt's packs where there is no protection diode but only in the first pack)

Sorry but that makes no sense ... I'm not sure what kind of "voodoo" @1RadWerkstatt makes with their custom made packs but standard KS packs have separate charging (Deans) and discharging (XT-60) plugs all joined in parallel between the packs. Would you mind explaining how exactly would the wheel even work if the battery packs would be "chained" from discharge port of one to charge port of another? I think there must be some misunderstanding here from what you've been told and how it really works. Maybe a connection diagram / drawing will explain what you mean exactly?

[Keith]

Guys, before this goes any further down a blind alley, a fully turned on MOSFET has an RDS value (resistance drain-source measured in milliohms typically 27mOhms or less, there is no significant voltage drop across a turned on MOSFET so whether they are series, cascaded, parallel or only one makes absolutely no difference.

Edited August 1, 2016 by Keith

[US69]

32 minutes ago, HEC said:

Sorry but that makes no sense ... I'm not sure what kind of "voodoo" @1RadWerkstatt makes with their custom made packs but standard KS packs have separate charging (Deans) and discharging (XT-60) plugs all joined in parallel between the packs. Would you mind explaining how exactly would the wheel even work if the battery packs would be "chained" from discharge port of one to charge port of another? I think there must be some misunderstanding here from what you've been told and how it really works. Maybe a connection diagram / drawing will explain what you mean exactly?

Sorry, too! :-)

But Chriull is absolutly right with what he says....even on some wheels:

 

Good example is the KS18 1360 wh....The big 680wh block under the board is connected directly to the board....

The both 340 wh packs  on the side/axis are connected to the 680 wh block, but not to the board directly...and they Charge the 680wh block...

The charging goes to the 680wh block...and this block charges the two 340wh blocks.

Hope i remember it correctly :-)...

...this all has been discussed before in another thread...as always i am to stupid to find it :-(

 

As far as i know this is not the case in 680/820wh configs on KS14/16....here you have a "true" parallel Connection...

 

[HEC]

42 minutes ago, KingSong69 said:

Good example is the KS18 1360 wh....The big 680wh block under the board is connected directly to the board....

The both 340 wh packs  on the side/axis are connected to the 680 wh block, but not to the board directly...and they Charge the 680wh block...

The charging goes to the 680wh block...and this block charges the two 340wh blocks.

Hope i remember it correctly :-)...

...this all has been discussed before in another thread...as always i am to stupid to find it :-(

 

As far as i know this is not the case in 680/820wh configs on KS14/16....here you have a "true" parallel Connection...

Well the thread was originally about KS-16 (though sidetracked  a bit by @esaj and myself). KS-18 is quite unique and not a typical example of EUC / battery wiring. Plus I fail to see any benefit to such "weird" / non-standard wiring of the battery packs as apart of few "saved" plugs and cables it has mainly downsides if one battery pack charging other during charging and then vice versa during discharging as all it creates is unnecessary losses. Still would like to see full wiring diagram for that to exactly understand how is it all connected as verbal description from bot you and @Chriull is confusing.

[US69]

1 hour ago, HEC said:

Well the thread was originally about KS-16 (though sidetracked  a bit by @esaj and myself). KS-18 is quite unique and not a typical example of EUC / battery wiring. Plus I fail to see any benefit to such "weird" / non-standard wiring of the battery packs as apart of few "saved" plugs and cables it has mainly downsides if one battery pack charging other during charging and then vice versa during discharging as all it creates is unnecessary losses. Still would like to see full wiring diagram for that to exactly understand how is it all connected as verbal description from bot you and @Chriull is confusing.

Nobody said, that this config has any advances and that it is not weird....

In the contrary i also do not know which benefits it has....as i am no "electrical" specialist....

 

Unfortunatly i am not good in drawing any diagram....but after searching my a...off .....i even found the original discussion about it: (Title is just wrong..ist about the KS18)

 

 

[HEC]

32 minutes ago, KingSong69 said:

Unfortunatly i am not good in drawing any diagram....but after searching my a...off .....i even found the original discussion about it: (Title is just wrong..ist about the KS18)

I've went through the whole of that thread and frankly there is no clear conclusion to how exactly are those multiply packs connected. If the 3 battery packs are really "daisy chained" by connecting discharge output of first to charge of second and so on it's the most idiotic electronic design in the world as it would mean that cells in the first pack are degrading much faster than in second and third and also the cells in second more than in third due to the constant recharging of each other. I can't simply believe that someone sane would ever design something like that

Only reasonable explanation IMO is that all 3 packs are in fact connected in parallel with all grounds common and also +V lead common through the whole chain with BMS of each pack "tapping" into +V line via protection diode or MOSFET to charge it's cells and via separate output protection to provide discharge voltage on the same +V line if there is no charging voltage present or if it's too low - so basically it's either passing through the charging voltage (if connected to charger and the voltage difference is above certain limit it's charging it's cells) or just outputting the cells voltage to the "common" V+ line - similar way like these lovely modules ...

[US69]

17 minutes ago, HEC said:

I've went through the whole of that thread and frankly there is no clear conclusion to how exactly are those multiply packs connected. If the 3 battery packs are really "daisy chained" by connecting discharge output of first to charge of second and so on it's the most idiotic electronic design in the world as it would mean that cells in the first pack are degrading much faster than in second and third and also the cells in second more than in third due to the constant recharging of each other. I can't simply believe that someone sane would ever design something like that

Only reasonable explanation IMO is that all 3 packs are in fact connected in parallel with all grounds common and also +V lead common through the whole chain with BMS of each pack "tapping" into +V line via protection diode or MOSFET to charge it's cells and via separate output protection to provide discharge voltage on the same +V line if there is no charging voltage present or if it's too low - so basically it's either passing through the charging voltage (if connected to charger and the voltage difference is above certain limit it's charging it's cells) or just outputting the cells voltage to the "common" V+ line - similar way like these lovely modules ...

As i have said: I have no clue of These electronics...

But: In the end i have a Little trust into what KingSong or even 1Radwerkstatt is doing.

 

I do not have my KS16 here, but i was present, when the 680wh Batterie was taken Out of the wheel...and how the wiring looked.

The KS 16 has the same Batterie Connections/Wiring than in the shown Pictures of the KS14 680wh....(as i remember it)

 

If some of the experts, like @1RadWerkstatt would jump in and explain why we dont see any "y-Adapters" , it would be easier....now it is just guessing...

Even this old thread was a Kind of unfinished, why and how exactly this is working...

[HEC]

3 minutes ago, KingSong69 said:

If some of the experts, like @1RadWerkstatt would jump in and explain why we dont see any "y-Adapters" , it would be easier....now it is just guessing...

Even this old thread was a Kind of unfinished, why and how exactly this is working...

Well - I'm due to open my KS-16 soon once the replacement controller board arrives from @Jason McNeil so I'll have a poke around to see what KS did there ...  Stay tuned.

[Jason McNeil]

@esaj, @Chriull @Keith are you guys able to infer how paralleled the KS BMS is based is image? I was told the original one is on the left & the 'new' design on the right... 

Will get double confirmation about this later this evening.

 

Edited August 1, 2016 by Jason McNeil

[HEC]

24 minutes ago, Jason McNeil said:

@esaj, @Chriull @Keith are you guys able to infer how paralleled the KS BMS is based is image? I was told the original one is on the left & the 'new' design on the right... 

I was trying to "decipher" anytthing from that picture in the original thread but the glare doesn't help plus having other side would help too ... also maybe better resolution.

24 minutes ago, Jason McNeil said:

@esaj, @Chriull @Keith are you guys able to infer how paralleled the KS BMS is based is image? I was told the original one is on the left & the 'new' design on the right... 

I was trying to "decipher" anytthing from that picture in the original thread but the glare doesn't help plus having other side would help too ... also maybe better resolution.

EDIT: Looks like forum is playing up doubling the posts ...

Edited August 1, 2016 by HEC

[Chriull]

6 hours ago, KingSong69 said:

...If some of the experts, like @1RadWerkstatt would jump in and explain why we dont see any "y-Adapters" , it would be easier....now it is just guessing...

Chris is using this configuration, because it is the only one which assures cell overvoltage protection by the bms if more than one pack is used. With connections at charge and discharge wires ("real parallel" packs, not cascaded) one cancels the possibility of the bms to cut charging once one cell reached the threshold - because the pack still gets charged via the discharge wires...

so cascading is the only professional solution - one just have to take care, that the  input(charge) circuit can take the whole current and especially the reverse voltage protection diode only is allowed to be in the first pack!

i can illustrade this in further detail later this week, once i am on my computer again if neede/wanted - on the iphone its hard to make links and write longer posts...

Edited August 1, 2016 by Chriull

[Keith]

@Jason McNeil, I agree with @HEC, cannot quite see enough of the the board due both glare and lack of resolution beyond the obvious difference that the right hand board seems to have P+,P- (power out) and C+,C- (charge in) completely seperate whilst  P+ and C+  seem to be common on the left hand board. That latter configuration is not unusual, any protection circuitry does seem to commonly be on the negative side. Whether, in fact tracks connect P+ and C+ together though I cannot see.

Not sure, even with higher resolution, whether it would be possible to tell anything about how the boards are parallelled. Bottom line is that as long as any tracks, wires and components between P+ & C+ and between P- & C- are capable of comfortably handling the maximum current flowing though them whilst powering the wheel it really  does not matter whether the packs are cascaded or just parallelled. What can be identified on both of those boards is that the charge and power wires are all of the same thickness, not, as is more usual, thinner on the charge side where max current (I.e. Just charge current) would normally be much lower.

[Keith]

9 minutes ago, Chriull said:

With connections at charge and discharge wires ("real parallel" packs, not cascaded) one cancels the possibility of the bms to cut charging once one cell reached the threshold - because the pack still gets charged via the discharge wires...

This assumes that the BMS charge input protection cuts power to that pack when the batteries are fully charged.

So far I, personally, have seen no schematic which has that functionality. The BMS schematics I've seen rely on the charger clamping the input voltage at the maximum input (I.e. 67.2V for a 16 cell pack.). The balance circuit is across each individual cell (or group of parallel cells) and shunts current around that cell once it reaches 4.2V thus clamping that cell at 4.2V whilst letting lower cells continue to charge. As the entire pack voltage climbs closer and closer to 67.2V then current flowing reduces until once both pack and charger are at 67.2V no further current flows. The charger will show charge complete once current drops below a predefined minimum, something like 100mA.

As far as I can see BMS input protection, which is usually a MOSFET, not a diode is about preventing reverse polarity or shorts circuits across the charge pins, not shutdown on over-voltage. Obviously there may be some more sophisticated designs out there but I don't think the run of mill bog standard BMS is that clever?

BTW, that is why I think putting your wheel on charge overnight in your house and then going to bed is REALLY not a good idea. If the charger fails to regulate to 67.2V one night, you might never get to find out about it! I have NEVER done that.

[Jason McNeil]

@HECCell manufacturers suggest a charging to up to 4.1v for eBikes, which would be 65.6v for the pack. To get to 80% capacity & the 4x increase in cell life-span, Justin from eBikes.ca, has a recommended set point of 4.05v /cell

[HEC]

22 hours ago, Jason McNeil said:

@HECCell manufacturers suggest a charging to up to 4.1v for eBikes, which would be 65.6v for the pack. To get to 80% capacity & the 4x increase in cell life-span, Justin from eBikes.ca, has a recommended set point of 4.05v /cell

Yes - I was l reading up the linked thread before. While 4.05V is very conservative and will definitely increase the battery life greatly based on the rider's need for longer range it's still fairly safe to charge cells to 4.1V or even 4.15V without decreasing the cell life significantly and it's up to each individual owner or specific planned ride to decide if you want / need to trade of a little bit of battery life for longer range or (most importantly) your safety especially if you're larger / heavier. I'd need to dig up the Charge Doctor datalog from few weeks back where I was charging the wheel from 6% all the way to 100% (where remaining current was about 20 mA I think) using the 5A fast charger and the point where charging changed from CC to CV mode and charging current started to drop quickly after 4A that is IMO optimal "compromise" between extending the battery life and not decreasing your range too much. For me it's using the new version of Charge Doctor by setting cut-off voltage to 66.4V which will result in 87% capacity reported by wheel / app after charge (so slightly below 4.15V per cell as the overall battery voltage is a tad lees then set cut off voltage once the charging stops). If you have pre 2.03 version of CD you can set the current cut-off to about 3.7 - 3.8A with about same result (I'll verify the exact current once I'll re-plot the charging graph). The benefit of charging the battery using CD with voltage (or current) cut-off comparing to using the 64.8V switch option on the @Jason McNeil's fast charger is that the charging is running at the "full speed" almost to the very same end (depending on your cut-off settings) why the latter will "slow" down towards the end once the charging mode changes from CC to CV but of course you'd need to invest extra money to purchase the CD. Also unlike CD the charger will actually not stop charging once the "charging" LED changes from red to green and will continue to supply some low current to the battery / wheel which in some rare cases like faulty BMS can lead to unwanted effects or even battery damage so you should never leave charging wheel unattended for extended period of time and switch of the charger or pull it off mains once charging has finished.

In conclusion - everyone shall / will find some fine balance between either maximizing your battery life by keeping your battery charger level always between 20 - 80% for it's maximum life (with full charge every 15 - 20 charges to assure proper balancing of the cells) on account of decreased range to almost half or go to other extreme with charging always to the "brim" (e.g. leaving the charger on for another 2 - 3 hours after charging LED turns green or using CD until the charging current drops below 20 - 10 mA) and riding the wheel until it "drops dead" with about 2% of battery capacity for maximum range though on account of drastically decreasing your battery life. There will be minimum users on either extreme and most will float somewhere in the middle.

Kudos to @Jason McNeil for investing his time to do all technical research in addition to his already overwhelming distributor's duties and to offer customers not only unique / bonus features with his products like fast chargers but also the technical background info to go with that via his blog and here in forums. I just wish more distributors and resellers were as proactive and dedicated to their customers as Jason.

Edited August 2, 2016 by HEC

[1RadWerkstatt]

Short info from us:

Y-Adaptery bridge all safety feature´s from BMS - Chirull has correct information

Y-Adapters are wrong and not ok....in last conclusion you risk a battery fire --> overcharging is possible and a short circut gives extrem energy free

Battery´s from us use only on first charge input one "diode" for safety reverse polarity on charging connector and charger itself.

Battery packs than parallel trough mosfets (low resistance)

 

When charger not switch off at 67,2V BMS cut charge mosfet over 4,24V at only one Cell and all is fine but only with right connection.

When you have a drift in cell´s and Y-Connection you overcharge this Cell´s with highest voltage BMS charge mosfet from one BMS swtich off and the second parallel BMS does it not and bring the Voltage to overcharge Battery during Y discharge port back....

 

1RadWerkstatt