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Energy Efficiency of EUC


Daan

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The VC3 cells are the same ones that were in your original Firewheel, Sony has a max output rating of 10A for these.

http://www.dampfakkus.de/akkutest.php?id=106

Even Solowheel's own product page has two different power rating, 1800W & 2000W. What's not certain is how the batteries are configured, since 16 of these cells in parallel is only 132Wh, with 19 cells the capacity numbers fit, but the resulting voltage is somewhat unusual...   

I'm not 100% sure, but I think Sony has at least V3 (used in Firewheel) and VTC3, which are two different types of cells. VC3 would seem to be a third different type of cell, at least I found different specs for all of these three cell-models. Haven't found much info on VC3's from reputable sites, mostly just resellers. The specs seem to differ enough to make me believe the Sony VC3 is its own cell-model, different from V3 and VTC3. But then again, it could also be just a typo on the Solowheel-pages of either V3 or VTC3, and the VC3-cells for sale could be some pirate copy of Sony-cell, that actually deliver nothing of what they promise... ;)

 

Sony US18650VC3 2000mAh

Nominal Capacity    2000mAh     
Minimum Capacity    1900mAh     
Nominal Voltage    3.7V     
Charge Voltage    4.20V±0.5V     
Cut off Voltage    2.5V     
Maximum Charge Voltage 4.25V
Continuous Max. Charge Current    2.15A
Continuous Max. Discharge Current    18A     (Some places say 20A)


Sony US18650V3 2250mAh

Nominal  Capacity  2250mAh
Mininum  Capacity  2200mAh
Nominal Voltage 3.7V 
Charge Current 2.15 A 
Discharge Cut-off voltage 2.75 V
Continuous Max. Discharge Current 10A

 

SONY US18650VTC3 1600mAh
 
Norminal Capacity  1600mAh
Minimum Capacity 1500mAh
Nominal Voltage : 3.7 V
Charge current 10A
Continuous Max. Discharge Current 30A

 

Edit: I recall reading somewhere that the Solowheel voltage is really around 55V, then it should be made from 15 cells: 15 * 3.7V = 55.5V. And then if the 155Wh number mentioned in their site is correct, and they use a single pack (15S1P), the capacity of a single cell should be around 155Wh / 55.5V = 2.79Ah => around 2800mAh. I don't know if Sony even has 2800mAh -cells, especially with high discharge rates the 1800W of power would need...

If it is 60V, then it should be 16 cells and the cell capacity should be 155Wh / 59.2V = 2,62Ah => around 2600mAh, then they could be using the 2600mAh Sony US18650VTC5's (30A continuous discharge),  but then again, why would they speak of "VC3"/"Sony VC3"-batteries on a couple of places in the spec-pages... Something doesn't add up here :P

Edit2: From the italian Solowheel-site, I got this info for Xtreme-batteries:

Battery:  Sony VC3, Lithium-ion 3.8H., 160 Wh - 1000 charge cycles 

If the "3.8H." marking there means amp-hours, I would then think there are two parallel packs with 1900mAh cells each.

Also, from the french site, I caught this (Solowheel Classic):

Battery:

  • LiFePO4 - 1000 cycles
  • 52.8V x 4Ah
  • Sony VC3 cells
  • 45 min to 90 min to fully load
  • Output: 30A max (very safe rider to catch during an emergency)
  • Input (for load): max 3A

So it would seem that at least the newest generation Classic uses the same Sony VC3-cells, which are LiFePo? Yet the VC3-specs I've found give too high voltage for it to be LiFePo?

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Good researching Esaj! B)

This may explain at least some of the specs. I know that on the Xtreme it says it has Li-ion batteries now (not LiFePo like the classic). Given Jason's remarks I may ask Inventist again to get some clarification. Actually, I saw Shane Chen is in Seattle this Sunday so I may be able to ask the man himself :) 

 

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Good researching Esaj! B)

This may explain at least some of the specs. I know that on the Xtreme it says it has Li-ion batteries now (not LiFePo like the classic).

Thanks, I've become some sort of a battery geek lately while doing research for the Firewheel custom-packs... ;) :D  Not that I can claim to be any sort of expert on batteries or cells. "Lithium-ion" or "Li-ion" seems to actually be a blanket-term that covers pretty much all the chemistries (LiCo, LiMn, LiFePo, LiNiCoAl, LiNiMnCo, LiTi... and others), except LiPo (Lithium Polymer).

Given Jason's remarks I may ask Inventist again to get some clarification. Actually, I saw Shane Chen is in Seattle this Sunday so I may be able to ask the man himself :) 

That would be nice, if you get the chance. :) I don't know if I really have any use for the info, but have a perversion of picking up all sorts of trivia from the field of EUCs :D

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I received the Charge Doctor from hobby16 today, and rode the Firewheel to as empty as I could... 2-4m/s winds, around 17 Celsius (62F) when I left, 14 Celsius (57F) when I got back. First stop at around 22.2km accelerating uphill, then a few hundred meters from my home, again going uphill, still managed to start it after walking up, and rode some hundreds of meters on more or less level street, until it finally seemed "empty enough". Plugged it into charge with Charge Doctor and captured the output. It took over 3,5 hours before the charge current dropped to 0mA (so I guess they're fully balanced now), the voltage started from 56.2V and climbed to 67.8V, where it stood for the rest of the load. In total it could cram 267.3Wh into the batteries:

Firewheel-charge.thumb.png.d9d27af6c2e3b

My total trip was pretty precisely 24.5km (15.22 miles) at an average speed of 19km/h (so not that fast riding). I began the trip by going uphill most of the time (climbed near one of the highest points around here), and it contained lots of varying riding (some fast parts, near 30km/h on empty bikelanes with good visibility, and lots of slower riding around and below 20km/h). This would give me an average usage of 10,91Wh per kilometer, or 17.56Wh per mile.

EDIT: Here's the charge-log as pure CSV-file (cleaned up some garbage from the beginning and end, when the Charge Doctor was powered up & down), in case someone wants to play with it in Excel or whatever:   20150717224700_Firewheel_charge.txt

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Sony US18650VC3 2000mAh

Nominal Capacity    2000mAh     
Minimum Capacity    1900mAh     
Nominal Voltage    3.7V     
Charge Voltage    4.20V±0.5V     
Cut off Voltage    2.5V     
Maximum Charge Voltage 4.25V
Continuous Max. Charge Current    2.15A
Continuous Max. Discharge Current    18A     (Some places say 20A)

 

I found on the Solowheel website (http://www.solowheel.com/product/xtreme) that they use "Sony VC3" batteries so those must be it. Also, it is a Lithium-Ion battery (LiIon) not a LiFePo4 battery -- that kind was only used on the 'classic' model. Don't why they switched. Given the high continuous discharge current, it means:

1 cell = 1900mAh, at 3.7V that is 7wh per cell, which is 22 cells for 155wh.

With 22 cells, we get 3.7V x 18A x 22 = 1465W continuous power

(with much higher peak power which can be 30A for example. A reply by inventist seemed to imply that limit peak power to 1800W on the main board?)

If I ever take the wheel apart I will take a look in the battery pack to see if I am right -- and hey, perhaps Shane is able to answer this this afternoon B)

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I found on the Solowheel website (http://www.solowheel.com/product/xtreme) that they use "Sony VC3" batteries so those must be it. Also, it is a Lithium-Ion battery (LiIon) not a LiFePo4 battery -- that kind was only used on the 'classic' model. Don't why they switched. Given the high continuous discharge current, it means:

1 cell = 1900mAh, at 3.7V that is 7wh per cell, which is 22 cells for 155wh -- these are probably set in parallel to get the 3800 mAh as specified by the Italian site.

With 22 cells, we get 3.7V x 18A x 22 = 1465W continuous power

(with much higher peak power which can be 30A for example. A reply by inventist seemed to imply that limit peak power to 1800W on the main board?)

If I ever take the wheel apart I will take a look in the battery pack to see if I am right -- and hey, perhaps Shane is able to answer this this afternoon B)

I'm not so sure if the VC3-specs I found are the correct ones... 

Do note that "Li-Ion" is an umbrella term for all the lithium-chemistries (LiCo, LiNm, LiFePo, LiNiMnCo, LiNiCoAl etc), except LiPo (Lithium Polymer, different than LiFePo, which is Lithium Iron Phosphate). But, the problem is that LiFePo nominal voltage is LOWER than 3.6/3.7V (usually LiFePo is 3.2-3.3V nominal), so the the specs I found for VC3 could be wrong, the nominal voltage is too high for them to be LiFePo. 

At least the newest revision of Solowheel "Classic" supposedly also uses the VC3's, and they at the same time claim they're LiFePo: 

  • LiFePO4 - 1000 cycles
  • 52.8V x 4Ah
  • Sony VC3 cells

52.8V total at 3.3V per LiFePo-cell would come to exactly 16 cells.

 

And please, do ask Shane, if you get the chance  :)

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If you speak to someone from Solowheel can you also find out how the battery-pack is configured? If not mistaken, the charger is 58v, but 22 of these cells as a single series is 92.4v (too high) & divided into two parallel sets is only 46.2v (too low). 

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I'm not so sure if the VC3-specs I found are the correct ones... 

 

I think you are right since I found the same specs everywhere; for example: http://www.evvatech.com/sdp/1015379/4/pd-4967686/11959834-2584585/Lithium_ion_battery_US18650VC3_AKKU_18650_2000mAh.html

Unfortunately, I wasn't able to find the real Sony data sheet anywhere. Ah well.

If you speak to someone from Solowheel can you also find out how the battery-pack is configured? If not mistaken, the charger is 58v, but 22 of these cells as a single series is 92.4v (too high) & divided into two parallel sets is only 46.2v (too low). 

If I get the chance I will ask B)  Not sure though as it is a general meetup so I don't know how much we can talk and ask questions.

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If only 16 cells, the capacity numbers are definitely wrong. 3.7v x 2Ah = 7.54Wh/cell x 16 cells = 120.64Wh. In reality usable capacity is always less than this formula, 

Using the case of the V3 relative, rated at 2.25Ah, has a value of 7.627Wh drained down to 3v.http://www.dampfakkus.de/akkutest.php?id=106 

 

This is quite insightful: the data on the Solowheel.fr site http://www.solowheel.fr/features/, lists the battery capacity as 4Ah & 51.8v. This strongly implies that the configuration is 2p14s for a total of 28 cells & the actual capacity is 211.12Whs for the S300/XTreme. 

Why then would they be advertising the capacity as 155Wh or 160Wh? Perhaps to make it past the Airline restrictions? These facts would also explain the extraordinary range that Daan has reported. 

5: Model S300: Push button instead Switch button

1500W motor / 51.8V 4Ah Sony VC3 Li-Ion battery (+60% extra capacity) / board V2 / Kenda tire / notch for the tire inflation / aluminum push button / black or white color (optional printed figure) / charger 58V 2A compact fanless with 2 LED: 1 red LED (power) and 1 green (not charging) or red LED (charging) / 2 built-in driving modes: soft or hard

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@hobby16, that's very interesting indeed, I was under the impression that SW were offering the upgraded 20kph max speed free-of-charge; to demand that owners payout another 70€ after dishing out $2,300 on the XTreme is a bit rich.   

Where did you hear this?   I heard there is a "faster" firmware for the classic, but that is certainly not available from Inventist themselves.  I heard that the dealer in Paris can do this upgrade, but when I asked Inventist about this they said that couldn't/wouldn't install this firmware for me.   I also doubt there is a fast firmware available for the xtreme yet.  Have you heard about one?

 

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This is quite insightful: the data on the Solowheel.fr site http://www.solowheel.fr/features/, lists the battery capacity as 4Ah & 51.8v. This strongly implies that the configuration is 2p14s for a total of 28 cells & the actual capacity is 211.12Whs for the S300/XTreme. 

Why then would they be advertising the capacity as 155Wh or 160Wh? Perhaps to make it past the Airline restrictions? These facts would also explain the extraordinary range that Daan has reported. 

ha, that is quite interesting Jason! B)  the plot thickens :ph34r:  lol.  Hmm, if I assume a drained battery with 2.75V, then 28 * 2.75V * 2000mAh = 154Wh, or if I take 3V, then 28 * 3V * 1900mAh = 160Wh.... hmm, perhaps creative calculations :D  Or, perhaps the batteries contain less lithium -- the real airline restriction is in grams of lithium (I believe 8grams?) and that is translate to 160Wh but perhaps newer technology caught up with this??

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Thanks, it's funny, I'm working on a small project to install a data-logger for just this purpose, recording exactly how much energy each eWheel consumes before 'get-off-now' is signaled & the power profile under different scenarios.
From the evidence of range experience, I would bet you a beer there's more capacity than 160Wh in it B) For Airline rating capacity, the spirit is really the energy contained within the cells, rather than the energy the riders uses. In any case, it's nice to know you're probably getting more than you expected...  

Edit: credit has to go to @esaj, in another post he already made the connection of 2p14s.

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Well, I met Shane Chen (and his daughter) today and we all went for a ride with everyone who showed up -- very fun (@hobby16: I did pass on your message :-) ). Moreover, they are really kind and friendly -- great people; Shane is really a genuine inventor with deep technical knowledge and loves talking about the fine points of the design. His daughter is super skilled in the Solowheel and tried to teach me some tricks on how to ride backwards -- we'll see if I can manage that :D Anyway, here are some interesting nuggets of Solowheel knowledge :)

  • When braking very hard, or going downhill very slow, instead of using regeneration to absorb the energy, the wheel will actually switch to reverse mode to give extra braking power -- this is why you won't get an overcharge warning when going downhill with a full battery if you go very slow.
  • The Solowheels have a custom designed BMS (battery management system) that will never cut-off the battery on its own -- instead it always sends a signal to the main board which decides what to do -- very safe design.
  • I got the impression that the Xtreme has 28 cells (2p14s) of Sony VC3's -- you do the math ;)  That explains the range too. The batteries can safely deliver 20A continuous and 40A peak current -- but since they are in parallel the batteries can deliver up to 80A peak current (which is regulated by the main board).
  • The batteries on the Xtreme still function up to 36V but the main board already starts warning for low battery at 45V -- pretty big safety margin.
  • To avoid the overcharge warning going downhill with a full battery, the latest chargers will charge a bit less than 100% to have some safety margin; later one can adjust this using the upcoming Bluetooth app. I saw a preview of the app and  it showed the percentage of the battery power left -- more useful that the current battery indicator (the blue light up front).
  • The Orbit is coming soon... perhaps in 2 or 3 months...
  • Shane said current wheels can still not catch you if you just fully lean forward for example; even 1800W motor is not enough. You need at least 3000W to make a very robust version -- with full uncontrolled leaning forward, you may need up to 10.000W to catch that. In the future with better batteries this may come some day. Also, the Orbit motor design is more efficient and more powerful; Shane quoted current motors (brushless DC) are about 50-80% efficient (depending on speed) while the new Orbit motor gets over 93% efficiency. The Xtreme is more efficient than the classic because the motor is more powerful and the cruising speed is therefore more optimal.
  • In France, they sell indeed a faster version of the Xtreme if you sign a waiver (15mph!) -- let's hope it will become available in the US too! B)

Ok, that is it for now :) 

note: anything stated above is purely my own opinion and is not an official statement made by anyone.

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Thanks Daan, Did Shane explain the reasons for under-reporting the capacity of the battery-pack? The regulations set out by the international airline authority IATA are quite clear that a battery-pack must not exceed 160Wh. Doesn't this render both the new S300 & XTreme non-airline compliant? 

https://www.iata.org/whatwedo/cargo/dgr/Documents/lithium-battery-guidance-document-2015-en.pdf

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  • The Xtreme has 28 cells (2p14s) of Sony VC3's -- you do the math ;)  That explains the range too. The batteries can safely deliver 20A continuous and 40A peak current -- but since they are in parallel the batteries can deliver up to 80A peak current (which is regulated by the main board).

Ok, so it is 14S2P, certainly not LiFePo, and so the actual battery is around 52V * 2Ah * 2 packs (from what I've seen everywhere, typically the battery capacity is calculated with rounded nominal voltage and nominal capacity) = around 208Wh. Same as S300. So not LiFePo and not 155Wh, maybe the dealers aren't informed enough, as the Solowheel-sites in different countries seem to report different numbers/claim it's LiFePo.

At 20A continuous and full voltage, the theoretical maximum continuous output from batteries is around 2kW (51.8V * 20A * 2 packs = 2072W), and double that for pulse current.

Thanks Daan, Did Shane explain the reasons for under-reporting the capacity of the battery-pack? The regulations set out by the international airline authority IATA are quite clear that a battery-pack must not exceed 160Wh. Doesn't this render both the new S300 & XTreme non-airline compliant? 

Since a single pack is around 104Wh, and it does say a battery-pack (singular) must not exceed 160Wh, it could be still ok for planes... but not sure, if it's true, then there are more wheels that are ok for flying (the one's which use 132Wh packs). If it's 160Wh for all battery-packs combined, then definitely not ok.

 

  • The batteries on the Xtreme still function up to 36V but the main board already starts warning for low battery at 45V -- pretty big safety margin.
  • To avoid the overcharge warning going downhill with a full battery, the latest chargers will charge a bit less than 100% to have some safety margin; later one can adjust this using the upcoming Bluetooth app. I saw a preview of the app and  it showed the percentage of the battery power left -- more useful that the current battery indicator (the blue light up front).

36V / 14 cells = 2.57V, which cuts it pretty close to critical voltage. Probably should avoid riding it that empty, 45v / 14 cells = 3.21V sounds safer. Overdischarging batteries can damage/age the cells faster. Not charging to full voltage is also good for the battery lifetime, even though you don't get the full capacity out of them then.

Thank you for the info! :)

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Using that logic would also mean that every EU is airline compliant, since every pack contains multiple parallels sets. 

To me the guidance is pretty darned confusing no matter how you read it. They talk about "cells", "batteries", and "packages" but I didn't see a definition for "package". There's a 5kg limit for batteries in a package. The one for "battery" says:

“Battery” means two or more cells which are electrically connected together and fitted with devices necessary for use, for example, case, terminals, marking and protective devices. 

I can see one interpretation of the F260 battery being two "physical batteries" wired in parallel, if the concern is related to the side-by-side proximity of multiple cells causing a chain reaction. However the IATA document definition would seem to exclude that possibility since the two physical clusters of cells are connected as a single unit with one BMS.

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Did Shane explain the reasons for under-reporting the capacity of the battery-pack?

Just to be clear, that post was just my personal impression of various things I heard from many people that were there -- please do not attribute this to anyone specific or official. Thanks! 

Again, my impression is that the rating is based on lithium content (i.e. like you said, "energy contained inside the battery") ; when the guidelines were written those were based on grams of lithium with 8g ~ 100Wh but technology has moved on and can do with smaller amounts to get the same 'rider' energy. Also it seemed the way things are set up that the packs are separately connected thru the main board and can be seen as two smaller batteries (which cannot be generalized to other brands btw)

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I have a bluetooth connected clamp meter but I haven't yet tried to measure consumption.

I had an idea how to measure electric car consumption:
- Measure consumption on constant velocities ( 5,10,15 km/h). Depends on how accurate you want the data to be. Interpolate the results you so have curve for all velocities.
- Measure consumption while accelerating at constant rate. Reduce the velocity/consumption you got from earlier phase. you have now consumption that is needed for accelerating.
- Measure consumption while decelerating at constant rate. Reduce the velocity/consumption you got from earlier phase. you have now consumption that is needed for decelerating. It might be negative.
- You can repeat phases 1&2 for different rates of accelerating&decelerating.

Of course this would work better for electric cars because roads don't affect their performance so much.

I'm pretty sure that the way you ride also affects a lot in consumption. If you ride smoothly, so that your body's center of mass remains at the same levels even if there are bumps, it gives you more mileage. Same thing with course corrections. If your course corrections are smooth and accurate, it gives you more mileage.

 

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New consumption test at lower speeds today on my Firewheel 260Wh. Same protocol than before  :

  1. Charge Firewheel to 100% (current drops to zero)
  2. Ride at low speed. Distance =  15.41 km,  mean speed = 12.4 km/h, values from my installed bike computer "wheelco".
  3. Charge again Firewheel up to 100%, energy measured by Charge Doctor = 149.6 Wh

To sum up results :

At 12.4 km/h mean speed, energy consumption is 9.7 Wh per km (149.6Wh per 15.41 km)

At 20km/h mean speed, energy consumption is 12 Wh per km (see my previous tests )

"mean speed" = trip distance / trip time

It was just for the purpose of numerical comparison since riding at 12.4 km/h mean speed is very very boring and quite time consuming even if sometimes, to have fun, I give a huge acceleration boost and look at the amazed eyes of bystanders.

I expected high speeds to hugely decrease energy efficiency, but given the numbers, I conclude it's not the case.

So I prefer 20km/h mean speed, with cruising speeds at 25km/h even if it incurs a 20% loss in energy efficiency, largely compensated by a gain of 60% in trip time.

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