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Msuper V3 1900, photos from Lukas gotway (MSX)


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44 minutes ago, Adel said:

Thanks @Hunka Hunka Burning Love And @Rehab1 for the info. I'll follow both of you advice to discharge the capacitors and connect the battery packs together before connecting to the board.

:blink:  Uh, it's better NOT to discharge the capacitors in order to avoid a spark I think.  That's sort of one of the take home messages.  With the caps charged, I think the control board voltage level is still closer to battery level voltage so there isn't as great a differential.  

It is the high difference in voltage that seems to illicit the spark as lots of electrons want to leap over the connector parts.  With a lower voltage difference there is less sparking potential.  That is why Litewave doesn't experience sparks as his caps likely are still charged when he swaps his packs.

That is, unless you need to handle the control board (eg. replace it or something) then discharging the capacitors might be a good idea to avoid an accidental shock to a finger.

 

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I’ve had no sparks at all after starting to make sure the packs are fully balanced before disconnecting or connecting them. I also always discharge my capacitors before doing any work on the EUC.

Balanced packs and the new connector should almost eliminate the risk. Don’t hesitate though, hovering at "almost connected" would provoke a spark even with everythin else being as it should.

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1 hour ago, Hunka Hunka Burning Love said:

:blink:  Uh, it's better NOT to discharge the capacitors in order to avoid a spark I think.  That's sort of one of the take home messages.  With the caps charged, I think the control board voltage level is still closer to battery level voltage so there isn't as great a differential.  

It is the high difference in voltage that seems to illicit the spark as lots of electrons want to leap over the connector parts.  With a lower voltage difference there is less sparking potential.  That is why Litewave doesn't experience sparks as his caps likely are still charged when he swaps his packs.

That is, unless you need to handle the control board (eg. replace it or something) then discharging the capacitors might be a good idea to avoid an accidental shock to a finger.

Hunka's right, it's the voltage difference that causes the sparking. Anti-spark plugs are the best option, but if not available, the capacitors should be charged over a resistor or the connection must be made really fast to avoid sparking. When connecting two battery packs together, it's best to charge or discharge both to same voltage, the capacitors will only draw a short jolt when they charge, but batteries with larger voltage difference can in the worst case cause the pack(s) to catch fire or explode, unless the connection is cut by the connectors destroying themselves.

The momentary power dissipation in the connectors is high enough to melt metal, as people whose connectors have melted can tell you. This is a 0.5F capacitor bank charged to 12V (around 0.01Wh) being discharged at once, the momentary power goes beyond 10kW (>10000W):

V8MpcbL.jpg

 

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56 minutes ago, Scatcat said:

I’ve had no sparks at all after starting to make sure the packs are fully balanced before disconnecting or connecting them. I also always discharge my capacitors before doing any work on the EUC.

How do you discharge the capacitors?

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7 minutes ago, em1barns said:

How do you discharge the capacitors?

  • Open wheel and disconnect the main plug from the batteries to the board (red/black cables coming from the board going into that yellow main connector, for Gotways).
  • Switch on the wheel until it goes dead due to lack of power. Capacitors empty!

I've never had any sparking (with discharged capacitors), just quickly and evenly plugged the batteries back into the board. Maybe luck is involved:efef015fe0:

 

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Ironically, not getting a big spark when connecting the battery to the main board (assuming you do not have any anti spark fitted) isn’t actually a good thing. These devices require good quality low ESR (Equivalent Series Resistance) capacitors on the battery input side (https://electronics.stackexchange.com/questions/109385/when-should-i-use-a-low-esr-capacitor).  It is this very low internal resistance of these capacitors that cause the spark as it allows them to charge almost instantly with massive current.

Those capacitors are necessary to smooth the voltage and prevent the voltage spikes that would otherwise occur and will, over time, damage components on the main board. So any main board that doesn’t give a significant spark as the battery is connected and those capacitors charge up hasn’t got very good quality capacitors fitted!

As  @esaj and other have said the correct, and only way, to prevent those sparks is to connect one side of the battery and then temporarily connect the other side of the battery via a resistor so that the capacitors charge slowly. So if you have got XT90 antispark connectors, these do have that resistor built in https://wheelspinmodels.co.uk/i/231725/?gclid=EAIaIQobChMIweK1-si02wIVxbHtCh2klwbbEAQYBiABEgLrzvD_BwE and it is important that YOU DO NOT CONNECT THEM AS QUICKLY AS POSSIBLE as they need a moment to charge the capacitors through the resister. Of course, if you have ordinary connectors, then connecting as quickly as possible is a must.

By the way, the conjecture above that the manufacturer connects with the batteries discharged to prevent a spark is unlikely as a low battery still has a significant voltage. It is much more likely they charge the capacitors first through a resistive lead.

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9 hours ago, Colorado CJ said:

I "almost" want to order the batteryless version from EWheels and swap my batteries back and fourth from my ACM2.

9 hours ago, Hunka Hunka Burning Love said:

This new batteryless option is a game changer.  If they can make their battery compartments standardized so the packs are easily switched between rides, I think they could sell additional units and bring costs down for everyone.  The only concern I have is the spark issue, but with the new anti-spark connectors hopefully that should reduce that danger.  If you could get these wheels for $1000 without the battery pack and put your old pack in, that really drops the should I / shouldn't I threshold for some people like @meepmeepmayer.  :whistling:

There really is an "official" battery-less option? HOLY ****!! When I asked Ian about this with an ACM2, he said GW wouldn't do it.

@Jason McNeil Ehmmmmmmm man *cough*... how about reopening that Euro store?:efee8319ab: Looks like your level of service is unprecedented, we could need that here, too! Or how much is shipping a battery-less wheel from the U.S. to the EU?

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1 hour ago, Keith said:

Ironically, not getting a big spark when connecting the battery to the main board (assuming you do not have any anti spark fitted) isn’t actually a good thing. These devices require good quality low ESR (Equivalent Series Resistance) capacitors on the battery input side (https://electronics.stackexchange.com/questions/109385/when-should-i-use-a-low-esr-capacitor).  It is this very low internal resistance of these capacitors that cause the spark as it allows them to charge almost instantly with massive current.

Those capacitors are necessary to smooth the voltage and prevent the voltage spikes that would otherwise occur and will, over time, damage components on the main board. So any main board that doesn’t give a significant spark as the battery is connected and those capacitors charge up hasn’t got very good quality capacitors fitted!

Close, but as with many things, not that simple in reality. Discharged low ESR caps will cause more significant current as the entire circuit has smaller total resistance, however, when the connection is done quickly, minimal or no spark should occur. But a spark can still occur with "higher" ESR (still in the hundreds of milliohms range) caps, if the voltage difference is enough to create high current, and/or multiple higher ESR caps are in parallel, lowering the total resistance. And as for example Rehab1's dead ACM board shows, it's not entirely a "good thing" to get a spark either. Upon inspection, it seems that likely the high current spike had caused a high voltage spike (like through some of the inductors in the switching step-down circuits or such?) that had fried the MCU itself.

For wheels, the low ESR caps make sense because of the need for sudden "bursts" of high current and to keep the voltage from dipping too much. The battery wires themselves have some resistance and inductance, the latter of which prevents very fast di/dt (current over time) changes, at which point the large caps on the board act as a "energy reservoir" to keep things running.

This is simplified still, though...

 

Quote

As  @esaj and other have said the correct, and only way, to prevent those sparks is to connect one side of the battery and then temporarily connect the other side of the battery via a resistor so that the capacitors charge slowly. So if you have got XT90 antispark connectors, these do have that resistor built in https://wheelspinmodels.co.uk/i/231725/?gclid=EAIaIQobChMIweK1-si02wIVxbHtCh2klwbbEAQYBiABEgLrzvD_BwE and it is important that YOU DO NOT CONNECT THEM AS QUICKLY AS POSSIBLE as they need a moment to charge the capacitors through the resister. Of course, if you have ordinary connectors, then connecting as quickly as possible is a must.

While it certainly does not hurt to connect the antispark connectors more slowly, the resistor in the connectors is fairly small ("These two-stage connectors put a 5.6 ohm resistor in series with the positive leads before making a direct connection and bypassing the resistor."). For example, rehab1's ACM board had two 1000uF / 100v aluminum electrolytic caps in parallel at the battery input. Paralleled capacitance adds up, so the total capacitance is around 2000uF (+-20% or whatever the tolerance on those were). There's a logarithmic (or is it exponential, I always mix them up) curve to the charging and equations to calculate the time it takes to charge up the capacitance with specific input values or the voltage it charges up to given specific amount of time, but for most cases, using a simple and fast "rule of thumb" with RC-constants is enough.

With 5.6 ohms of resistance and estimating that the rest of the resistances in the circuit (wires, connectors, capacitor ESR's etc) make it an even 6 ohms, and 2000 uF (= 2mF = 0.002F) we get an RC time-constant of

6 ohms * 0.002F = 0.012 seconds

Then using the "typical" table:

 

RC Charging Table

Time
Constant
RC Value Percentage of Maximum
Voltage Current
0.5 time constant 0.5T = 0.5RC 39.3% 60.7%
0.7 time constant 0.7T = 0.7RC 50.3% 49.7%
1.0 time constant 1T = 1RC 63.2% 36.8%
2.0 time constants 2T = 2RC 86.5% 13.5%
3.0 time constants 3T = 3RC 95.0% 5.0%
4.0 time constants 4T = 4RC 98.2% 1.8%
5.0 time constants 5T = 5RC 99.3% 0.7%

Already at 2 * RC, the capacitor is charged to 86.5% of the input voltage, and the current has dropped to almots one tenth from the start of charging. At 3-5 times the constant, the current is a fraction of the initial spike. With a time constant of 0.012 seconds (12 milliseconds), the capacitors are essentially fully charged before 1/10th of a second. Unless pushing the connectors in REALLY fast, it's unlikely you can get a spark with anti-spark connectors and these values. Still, like said, it certainly doesn't hurt to do it more slowly with anti-spark connectors. 

With normal connectors, the idea is to minimize the time of the "sweet spot" resistance at the connector ends, where significant current already flows to charge the capacitors, but the resistance at the connection is of a value that causes very high power dissipation at that spot. There you want to do the connection as fast as possible to prevent any sparking (assuming that you don't have anything to charge the caps more slowly beforehand with).

Ok, enough wiseassing about this... :P 

 

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:blink:  I think that was in English, but it could have all been in Swahili or Finnish.  I think it had to do with electricity or some sorcery stuff like that.  Not quite sure, but I'm agreeing with it all.  :thumbup:  Can't go too wrong betting on esaj or Keith.  My rule of thumb is when someone posts a chart, graph, or reference it kinda trumps posting a music video from a Pixar movie.

@esaj  You should end all of your posts with "<Mike drop!>"  :whistling:

 

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16 minutes ago, Hunka Hunka Burning Love said:

:blink:  I think that was in English, but it could have all been in Swahili or Finnish.  I think it had to do with electricity or some sorcery stuff like that.  Not quite sure, but I'm agreeing with it all.  :thumbup:  Can't go too wrong betting on esaj or Keith.  My rule of thumb is when someone posts a chart, graph, or reference it kinda trumps posting a music video from a Pixar movie.

@esaj  You should end all of your posts with "<Mike drop!>"  :whistling:

 

I could probably just post some made-up graphs and charts, throw in some technobabble and get away with it... ;) :whistling:

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anyone ever tried this dealer? Wheel Tech store:

https://www.aliexpress.com/item/Free-Msuper-X-seat-Gotway-Newest-Msuper-X-19inch-electric-unicycle-self-balancing-scooter-one-wheel/32865991297.html?ws_ab_test=searchweb0_0,searchweb201602_4_10152_10151_10065_10068_10344_10342_10343_10340_10341_10696_10084_10083_10618_10304_10307_10820_10821_10302_10059_100031_10103_10624_10623_10622_10621_10620,searchweb201603_25,ppcSwitch_3&algo_expid=0c2c2277-3f90-441e-a6e3-5aeaf5bacb57-35&algo_pvid=0c2c2277-3f90-441e-a6e3-5aeaf5bacb57&priceBeautifyAB=0

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On 6/8/2018 at 10:30 AM, Rhada said:

Technically yes, but my Tesla purchase from them was via their eBay store at the end of last year, which was before they also started to sell through AliExpress (which by the way now offers much better pricing). I had very good communication and service with that transaction (although the wheel did take quite a while to arrive) I have just received a pair of ACM pedals that I did order recently through their AliExpress store, so again another problem free transaction. I can tell you that I would confidently buy my next wheel from them via AliExpress and have already heard from them directly regarding placing an order for an Msuper X. At this stage, I am just waiting to hear/read reviews from some of the forum members on the wheel itself once people start to take delivery of their Msuper X.

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  • RagingGrandpa changed the title to Msuper V3 1900, photos from Lukas gotway (MSX)

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