QSMotor 4000W V3 17” Hub Motor Aprilia RS50 Conversion

Hi

I’ve been toying with the idea of converting an Aprilia RS50 for years and have finally sourced the donor bike. It’s in really good condition but I’m happy to have a go at converting to electric and then putting it back to gas later if it doesn’t turn out as expected. I know I need to cut the rear of the swing arm to get the QSMotor hub in and make up some adapter plates to secure it down, but I’ll use a spare swing arm/frame for this and keep the original so I can revert back.

Having looked around at other conversions, and done a couple of Stealth bike type eBike builds, I’ve ended up basing the build on the QSMotor 17” hub motor rated at 4,000w - I need to limit this to 4,000w so it can still be classified a 50cc moped in the UK. The bike is still registered with the DVLA as a 50cc and even has MOT for another 10 months so it should be relatively easy to change to electric on the V5 once it’s built and I’ve even got QSMotors to supply me with a certificate confirming the maximum continuous output rating of the motor is 4,000w

So the question and request for help from all you more experienced builders out there is my maximum speed design goals for this project. I want it to achieve 50 mph max which the donor bike can actually achieve as a 50cc petrol engined back as it’s been derestricted. I’ve spoken at length to QSMotors and studied the motor spec sheet for what would be the V3 motor, and understand I can easily get 50 mph out of it on something like an Aprilia RS50 (it’s a light aluminium frame) but I have to be running at 72v with a max output of 100A to achieve this speed.

I don’t have access unfortunately to anything like Leaf cells as I’ve struggle to source anything at decent cost, and so have gone to a couple of eBike battery pack manufacturers who can all produce me a 72v 30Ah - 40Ah pack using something like HG cells, but all of them are telling me if I push the pack/cells to anything above 60A max for any length of time I’ll end up with voltage sag and likely I will wreck the cells/pack quickly.

Any advice here on what I should be looking at for a battery pack? I’m not looking for massive range; 25 - 30 mile range is acceptable and average speed for this would be 25-30mph - the 50 mph design target is most likely only going to be used for 10 - 20% of the range tops. I’ve also got plenty of space in the frame for the pack itself particularly in the area where the 50cc engine is currently as this is covered by the fairings so I can get a decent sized rectangular pack sitting almost vertically low down in the bike which will help with keeping centre of gravity low, and the controller can be mounted in the area where the petrol tank is currently.

I’d also like to source a battery pack with BMS/Charger for max £900 - £1,000 - I can get the motor / controller for £600 so am looking at a total cost of parts for the conversion around the £1,500 mark.

Just to complete the picture QSMotors would supply a Kelly KEB 72601 controller with the motor. I know there are better controllers out there but looking at what I’d be running the motor at it seems acceptable. Again, any opinions/advice would be appreciated on this as well.

I’ve used a whole host of rpm/speed/tyre calculators to look at what the speed is I’m going to get at different A outputs at 72V. For reference the wheel/tyre combo is approx 18.8 inches in diameter.

Anything you guys can help with here would be most appreciated.

Hi

I’ve been toying with the idea of converting an Aprilia RS50 for years and have finally sourced the donor bike. It’s in really good condition but I’m happy to have a go at converting to electric and then putting it back to gas later if it doesn’t turn out as expected. I know I need to cut the rear of the swing arm to get the QSMotor hub in and make up some adapter plates to secure it down, but I’ll use a spare swing arm/frame for this and keep the original so I can revert back.

Having looked around at other conversions, and done a couple of Stealth bike type eBike builds, I’ve ended up basing the build on the QSMotor 17” hub motor rated at 4,000w - I need to limit this to 4,000w so it can still be classified a 50cc moped in the UK. The bike is still registered with the DVLA as a 50cc and even has MOT for another 10 months so it should be relatively easy to change to electric on the V5 once it’s built and I’ve even got QSMotors to supply me with a certificate confirming the maximum continuous output rating of the motor is 4,000w

So the question and request for help from all you more experienced builders out there is my maximum speed design goals for this project. I want it to achieve 50 mph max which the donor bike can actually achieve as a 50cc petrol engined back as it’s been derestricted. I’ve spoken at length to QSMotors and studied the motor spec sheet for what would be the V3 motor, and understand I can easily get 50 mph out of it on something like an Aprilia RS50 (it’s a light aluminium frame) but I have to be running at 72v with a max output of 100A to achieve this speed.

I don’t have access unfortunately to anything like Leaf cells as I’ve struggle to source anything at decent cost, and so have gone to a couple of eBike battery pack manufacturers who can all produce me a 72v 30Ah - 40Ah pack using something like HG cells, but all of them are telling me if I push the pack/cells to anything above 60A max for any length of time I’ll end up with voltage sag and likely I will wreck the cells/pack quickly.

Any advice here on what I should be looking at for a battery pack? I’m not looking for massive range; 25 - 30 mile range is acceptable and average speed for this would be 25-30mph - the 50 mph design target is most likely only going to be used for 10 - 20% of the range tops. I’ve also got plenty of space in the frame for the pack itself particularly in the area where the 50cc engine is currently as this is covered by the fairings so I can get a decent sized rectangular pack sitting almost vertically low down in the bike which will help with keeping centre of gravity low, and the controller can be mounted in the area where the petrol tank is currently.

I’d also like to source a battery pack with BMS/Charger for max £900 - £1,000 - I can get the motor / controller for £600 so am looking at a total cost of parts for the conversion around the £1,500 mark.

Just to complete the picture QSMotors would supply a Kelly KEB 72601 controller with the motor. I know there are better controllers out there but looking at what I’d be running the motor at it seems acceptable. Again, any opinions/advice would be appreciated on this as well.

I’ve used a whole host of rpm/speed/tyre calculators to look at what the speed is I’m going to get at different A outputs at 72V. For reference the wheel/tyre combo is approx 18.8 inches in diameter.

Anything you guys can help with here would be most appreciated.

you are not going to manage it for 1000 for the battery alone, that will cost more.

you can limit the battery amps to 55A and just make sure you got plenty of amps to trow at the motor to get as much power early.
otherwise you are trowing away a LOT of performance.
if you are going for that hard 4kW limit i would get as much volts as humanly possible and a kV rating to match so you can crank as much power into that motor from a dead stop. otherwise you would need to get way up to speed to get decent acceleration.
in my experice the police dont care as long as you dont drive faster then allowed or drive like a moron.

i would also get a KLS, much more quiet and smooth on low speeds.

Regarding speed don't worry. You can do 120km/h with these frames. As long as you have good front brake.

If you need only 80km/h you can make it with qs205 3kw. But it is 150mm axle so you would need to fabricate rear fork.
If you plan to use the same rear fork than qs273 4kw will do; to be even more dynamic with it. Roughly with 273 you can do 200A and 500A phase so running it with 100A is kinda on safe side.
If you already made your mind about controller than it is fine. If you not than you can check what controller has (FOC) field weakening. In that case you can take ~9kv hub and have better start start torque and a bit more speed with FOC when you need for short time. Of course there is someone who will tell that all windings have the same torque...

Also maybe you can get certificate for 4kw motor but instead put more kw motor (maybe 6kw1 7kw, 8kw). Just a thought... 4kw 273 will be ok.

Regarding cells. You don't need anything special if you really plan to discharge them only up to 100A. You can make battery from 18650 any shape your bikes frame needs. If you take 273 plan you battery for 200A, in case you will want to hot rod it latter. If would like to save some on battery but sacrifice cycle number consider - LiitoKala 26650 50A 5000mAh.
I got leaf 20S 72v 30AH myself. If we were neighbors we could have a deal, but now you will need find something locally if you need P&P leaf cell.
you can choose from number of available cells. If cell can constantly discharge 15A and you need 100A constant so make your battery:
21S 11P kinda low
20S 12P kinda low
22S 14P not bad
20S 16P not bad
20S 20P ok

You can make small battery (out of 300 cells or even less) with high discharge cells. Depends what you prefer; according how much big battery you need. How much speed, distance you want. Actually the more the better. If you want more or less standart stick to 20s and get as many parallel cells as you need plus few more.

Also your rim diameter is 17'' therefore 100/80-17 tire diamter will be aprox - 23.3inch (591.8mm), not 18.8inch.

So to reach 80km/h you need motor of 9kv (will reach 80km/h with field weakening enabled) - 11kv (will 80km/h without field weakening). So you can use any of these motors. If you plan to ride 80km/h say 10km distance than better choose 11kv.
If plan very occasionally run 80km/h than 9kv with field weakening is fine. 11kv would be more common choice. Majority would go with 11kv as they want speed.

It hard to advice something spefic as there is so many option to choose from.


battery for £900 including BMS and charger - doable.
2.7eu per cell * 400cells = 1080euro
or some more expensive cells like 3eu or 3.5eu per one peace.
smart BMS - 100euro (must have)
10A charger - 100eu

£600 motor and controller - doable but on low side as shipping may cost fortune.

Regarding pack AH. Lean tawords more AH than to 30Ah, actually put 45Ah. I want to say - don't make battery you bottlenek. Additional ~10AH is nothing comapred with rest bike and your weight. Plus your buddged for battery is good considering you can solder cells yourself.

Also want to note that your frame choise does not limit you to 80km/h. Considering frame you can go 120km/h as long as you have good front brake. Just saying.. for such speeds battery is drained pritty fast and everything gets more demanding as wind resistance rising fast the faster you go. Up to 70km/g it is very economic speed. So you plan to reach up to 80km/h is very economic approach. For such frame i would want 80km/ht too, maybe near up to 85km/h when fully charged.

Note: I removed my reply from your third thread on this topic, and put it here in the first one instead. If you really want help, don't make a whole bunch of threads for the same project, just use this one (especially since the others are duplicates of this one):

swiftyds said:

I’ve ended up basing the build on the QSMotor 17” hub motor rated at 4,000w - I need to limit this to 4,000w so it can still be classified a 50cc moped in the UK. The bike is still registered with the DVLA as a 50cc and even has MOT for another 10 months so it should be relatively easy to change to electric on the V5 once it’s built and I’ve even got QSMotors to supply me with a certificate confirming the maximum continuous output rating of the motor is 4,000w
<snip>
I’ve spoken at length to QSMotors and studied the motor spec sheet for what would be the V3 motor, and understand I can easily get 50 mph out of it on something like an Aprilia RS50 (it’s a light aluminium frame) but I have to be running at 72v with a max output of 100A to achieve this speed.

Click to expand...

Just so you know, that's 7200W (72 x 100) at average pack voltage (nearly 8400w when the pack is full, depending on voltage sag due to pack design and quality/age), so about twice the legal limit for your bike, as well as about twice what the motor is rated for. If the motor really is designed for 4000w continuous, then running it at 7200w continuous is going to heat it up significantly, and you may have to add cooling to it in one or more ways. See Justin_LE's thread for Definitive Testing of HEating and Cooling of Hub Motors for info on methods that have been proven to work, with test data.


This thread
https://endless-sphere.com/forums/viewtopic.php?t=85164
seems to be using the same motor and controller, if it's useful.

I don’t have access unfortunately to anything like Leaf cells as I’ve struggle to source anything at decent cost, and so have gone to a couple of eBike battery pack manufacturers who can all produce me a 72v 30Ah - 40Ah pack using something like HG cells, but all of them are telling me if I push the pack/cells to anything above 60A max for any length of time I’ll end up with voltage sag and likely I will wreck the cells/pack quickly.

Any advice here on what I should be looking at for a battery pack? I’m not looking for massive range; 25 - 30 mile range is acceptable and average speed for this would be 25-30mph - the 50 mph design target is most likely only going to be used for 10 - 20% of the range tops.

Click to expand...

Assuming 60-100wh/mile, depending on conditions, terrain, riding style, etc., then 30 miles will take 1800wh - 3000 wh; I'd assume the latter or higher for safe operating margin (to try to account for pack aging, detours, winds, etc). It may take more than that to do what you're after; you can play around with the Trip Simulator and Motor Simulator at http://ebikes.ca to help figure out your actual system's needs under the conditions you'll use it.

For a 72v pack, that's 41Ah+. But as you say, using the (possibly clone or recycled/etc versions of) "HG" cells, that may not be enough parallel cells to handle the current load. However, you could double the pack size, and thus also double it's C-rate along with it's capacity (which will potentially double your range as well).

Honestly, if you can get salvaged EV cells, you'd be better off...but if you can't, heavily overbuilding an 18650 pack could work too, as long as the pack builder is reliable and actually uses genuine cells and builds the pack correctly and well. (there's just a lot more potential failure points in a pack made of small cells).

Many thanks for the responses and apologies for over posting the same post!

I don’t know how I managed to get the diameter for the hub/tyre combo wrong - basic error there, particularly as I’ve got the donor bike in front of me and can clearly see it’s 23inches+!

I’d missed the other post using the same motor/controller as it was a smaller wheel but that’s proved very helpful. I’m also a lot more comfortable now as I’ve heard back from QS and they can produce me a 4kw motor with more windings to produce 50mph at 60A max.

Now the next issue I have is that I’ve discovered my swingarm drop out/gap for the rear wheel on the Aprilia RS50 is only 180mm which I can tell is going to be too small for the QS 17” which I believe needs a 200mm drop out/gap. I don’t want to go with a eBike motor which would be a smaller drop out so a bit stuck now. I’m trying to see if I can get a later model Swingarm for an Aprilia RS4 50 which can be fitted to my 2005 model and I understand is larger gap. I’m also trying to contact Manny the guy who was building a similar project and was using the same model type Aprilia RS50.

Thanks again for all the help here

Ask QS what Kv and windings they will make for you.
It will be interesting to foresee what dynamic to expect out of nominal 4kw hub.

Regarding smaller wheel. You too acquire smaller rim 14inch, 16inch, 17inch and adjust you wheel OD (overall diameter) buy choosing different tire sizes
100/80-16
120/70-16

flippy said:

...
you can limit the battery amps to 55A and just make sure you got plenty of amps to trow at the motor to get as much power early
...

Click to expand...

Sounds not realistic. How you can achieve that?
You take 11kv 4kw hub, tire OD 23"
Set battery Current 55amps, phase 500amps.
And expect good start, acceleration?

Although the motor is rated at 4KW it peaks at just under 8KW and others who’ve used this even in 16 and 17” motorcycle rims are claiming decent acceleration if the battery pack can output enough As for take off, and top speed in excess of 80 kmh.

I’ve managed to find a battery pack that would consist of 2 Lifepo4 38.4v 30Ah units in series that would give me 76.8v in total at 30Ah but the cells are capable of 10c without a problem so 300A max for short bursts of acceleration and to help getting up to top speed. Total pack capacity would be 2.3 KWh.

If you go back to my original post here, I’m only looking to get up to max speed of 50 mph (80 kmh) for approx 10-20% of my range of 25-30 miles (so 6 miles in total but in reality with traffic etc more likely 3 miles at top speed).

The only issue (there are always issues so should really refer to them as challenges as there is a way around everything !) is that the Lifepo4 packs are 17kg each so 34kg for the pack - over 2x what the weight would be for a Lithium Ion pack.

The combined weight of the 50cc engine, chain, sprockets, various ancillaries like radiator (it’s water cooled) and a full tank with fuel (all of which would be removed) is 35kg - 40kg so pretty much the same like for like but I was hoping for weight saving here to improve acceleration and top speed.

300A max for short bursts sounds very good. 34kg heavy but I'm sure this pack has its own advantages. Is that how these cells look? see pic.

Of course it is good motor. Wheel size is just a matter of Kv and vs. As you know small wheel wins over bigger because of mechanical advantaged ie better thrust. Not torque (Nm), but better thrust (kg, pounds).

You can do 23inch OD with 16 or 17 inch rim. You can do the same OD with 16 or 17 inch hub by choosing different tires. 120/80-16 100/80-17 etc... Just a though that you are not stuck only to 17 inch rim. Actually can you do 23inch OD with 14'' hub, but 1400mm tire might be too wide for your preference.

I've ridden way less of a motor - qs273 28mm. Even that was fun to ride. I'm not saying that it is not capable of decent
performance. I just noticed that you wrote, "...limit the battery amps to 55A and just make sure you got plenty of amps to trow at the motor to get as much power early..."
I understand what you mean, but this is not quite true what you wore about setting 55a battery amps and throwing a lot phase amps. That is: when you set 55A battery amps and a lot lot i.e. 500a phase amps you have no enough battery amps to generate these 500 motor amps. Where do you gonna get a lot motor amps if you set 55A battery amps... You will get up to 200a motor amps no matter what you set phase amps to be when you have 55A battery amps. Controller is like any power converted. It can generate certain power if you supply enough power to convert that certain power. It decreases voltage and than increases amps and vs.
In other words: If you want good acceleration, you need battery amps to be twice higher than 55A with 9kv.
If you get 13kv you will need even more battery amps for good acceleration (almost) as good as 9kv and will have higher top speed.

If you got 300A for short bursts than there is no point limiting it to 55A. Just set 120A batt and max phase or whatever controller will be capable and will have good ride whenever you need overtake or something. Anyways these max numbers are only for few seconds.

Many thanks - it’s actually this pack that I can get hold of......

I’ve just discovered the individual cells are these .ifr26650.

swiftyds said:

I’ve been toying with the idea of converting an Aprilia RS50 for years and have finally sourced the donor bike.

Click to expand...

It seems like a very nice and suitable frame for an electric build.
Plenty of space available, you'll just have to build a custom sub frame to support the battery. You won't have too much work to do, that's a good start.

swiftyds said:

Having looked around at other conversions, and done a couple of Stealth bike type eBike builds, I’ve ended up basing the build on the QSMotor 17” hub motor rated at 4,000w -

Click to expand...

Seems like a very good choice, 4000W is plenty, even if it doesn't sound like it is.

swiftyds said:

So the question and request for help from all you more experienced builders out there is my maximum speed design goals for this project. I want it to achieve 50 mph max which the donor bike can actually achieve as a 50cc petrol engined back as it’s been derestricted. I’ve spoken at length to QSMotors and studied the motor spec sheet for what would be the V3 motor, and understand I can easily get 50 mph out of it on something like an Aprilia RS50 (it’s a light aluminium frame) but I have to be running at 72v with a max output of 100A to achieve this speed.

Click to expand...

Yes, but it can be less than 72V if your controller can do flux weakening.
But I suggest you to go as high as you can regarding voltage, as long as you can find a good controller at an affordable price.
For a 4000W motor, I think the maximum power you can use for a controller should be around 20 000W. For instance, my bike is using a 3000W motor and is happy to run with a 16 000W controller. Doesn't heat much, but I'm at the very limit of what my 3000W can take reliably.

50mph will be no problem at all, at 72V you can expect even much more if your controller can do flux weakening. My bike reaches 120km/h (75mph), @72V and 120 battery amps.

swiftyds said:

I don’t have access unfortunately to anything like Leaf cells as I’ve struggle to source anything at decent cost, and so have gone to a couple of eBike battery pack manufacturers who can all produce me a 72v 30Ah - 40Ah pack using something like HG cells, but all of them are telling me if I push the pack/cells to anything above 60A max for any length of time I’ll end up with voltage sag and likely I will wreck the cells/pack quickly.

Click to expand...

I would recommend you to use the same pack I'm using (A123 40ah, LiFePO4). They are a bit heavy but they can deliver a lot of current without sagging much, plus they are very reliable and can last a long time. Maybe their only drawback is that they don't really like being cold (their voltage will drop a bit during winter, but you can come up with some clever way to warm them up if you want to).
I'm not entirely sure, but I think you could install two of these batteries in your frame, that would give you 72V and 80Ah, which would allow you to have a really great range (more than 120km for sure). Or just one if you want to keep the bike light (one battery is 25kg).

swiftyds said:

I’d also like to source a battery pack with BMS/Charger for max £900 - £1,000 - I can get the motor / controller for £600 so am looking at a total cost of parts for the conversion around the £1,500 mark.

Click to expand...

Last time I checked for someone on the forum I came onto this link:
https://www.ebay.co.uk/itm/28s2P-A123-AMP20M1HD-A-Prismatic-Pouch-Cell-for-electric-vehicle-3-6-kW-hr/143114951981?hash=item215250dd2d:g:mPEAAOSw5xhcVo7b

I think it matches your target price. Just add a ANT blueetooth BMS and you'll be good to go.
Don't believe the specs on the ebay page, this battery is capable of way more than whatever is stated in the descpription, some people on the forum made extensive testings of those cells and they are well know for being awesome. I have it on my bike for more than a year and couldn't be happier.

swiftyds said:

Just to complete the picture QSMotors would supply a Kelly KEB 72601 controller with the motor. I know there are better controllers out there but looking at what I’d be running the motor at it seems acceptable. Again, any opinions/advice would be appreciated on this as well.

Click to expand...

I never tried this controller myself, and I don't really know much about it. Kelly controllers are good spec wise, but they don't monitor the battery currents very well, if at all, which can sometimes be a problem because you might have BMS cutoffs.
Also, I'm not sure this one does flux weakening.
From what I see on the specs here: https://kellycontroller.com/shop/keb/

280A/phase will be weak. In my opinion if you want something decent 450A/phase should be the minimum. With your 4000W motor you can go to 600A/phase.
I use a Sabvoton controller which does a bit more than 500A/phase, but I cannot recommend it anymore since it seems the new version are not as reliable as the old ones used to be. Try to get a controller in the 500-600A/phase range, preferably capable of flux weakening if you want to be able to tweak your top speed.

So to sum up, my advice would be:
-Go for the motor you planned, just find a way to enlarge your swingarm (maybe by bending it slightly?)
-Go for the A123 battery, at whatever voltage you want between 72 and 96V, it's a no brainer.
-Go for an ANT bluetooth BMS in 300A version
-Find a good controller that can do flux weakening and battery current monitoring. If your battery voltage is 72V, then find a controller capable of at leats 500Amps/phase, if its 84V then maybe 350-400A/phase could be enough, if it's 96V then even lower should be fine.
Try to find a sinewave controller as they are quite nice to ride, especially under the rain (precise throlttle control).
Of course, find a controller you can program, so that you can pass the inspection (I don't know how the inspection is supposed to work in UK, but if you have a programmable controller then you can just lower the power output to pass it, then go back to full power once you passed).

Based on these specs, your motorbike would be equivalent to a good 250cc sportbike, or a low power 400cc.

Thanks for the link to the battery - looks like a nice pack and it seems to be holding up well for you.

I’ve looked again at the other Forum member who fitted the QS Motor 4kw hub into the same Aprilia RS50 frame and swingarm - they cut a slot in the rear of the swingarm that widened it enough to take the motor and then used plates either side to lock it down. Looks like it’s a way around the reduced width and so long as I can replicate the plates I should be OK.

Will look again at the controller based on what you’ve been getting out of the 3000w motor.

For UK as the bike is already registered it’s a paper exercise to convert to electric from gas - so long as the paperwork backs up the 4kw limitations of the motor then there shouldn’t be any inspection nor change in moped classification.

I’ve looked again at the controller and made a change to my order - I’ve gone for Kelly KLS7245H which includes Bluetooth support and is also sinusoidal so should be a bit smoother on take off. I understand it’s been used with the 17” QSMotor 4kw hub motor before and should wire up easily enough.

swiftyds said:

I’ve looked again at the controller and made a change to my order - I’ve gone for Kelly KLS7245H which includes Bluetooth support and is also sinusoidal so should be a bit smoother on take off. I understand it’s been used with the 17” QSMotor 4kw hub motor before and should wire up easily enough.

Click to expand...

Not a bad choice but you could have gone a bit higher like for instance the 7250H, which is only 8 dollars more expensive but goes to 400A/phase, or even the 7275H which does 500A/phase for around 50 bucks more, according to this link:
http://www.cnqsmotor.com/en/article_read/Brushless%20Controller,%20KLS7245H,24V-72V,350A,SINUSOIDAL%20BRUSHLESS%20MOTOR%20CONTROLLER/819.html

I'm not sure since I never actually tried it, (sometimes you get unexpected results in real life despite the theoretical figures), but IMHO 350/phase is a bit on the weak side.

For your reference, this is the one I'm using on my motorbike:
https://www.aliexpress.com/item/36-FEET-200A-Controller-Sabvoton-SVMC72200-controller-for-Electric-Bicycle-Motor-Bruless-DC-Controller/32827301253.html

I’ve asked them to come back to me on the higher A/phase rated version - It’s probably overkill for what I need right now but no harm future proofing the build if I can

Thanks for the quick response and your other comments so far

Can you do me a favour when you have time - could you post up a couple of pictures of your motor fixings to the swingarm on your bike? I know I need to modify the rear of my swingarm and have seen how Manny did this on his RS50 conversion but would be good to see how this is mounted in a wider swingarm.

swiftyds said:

I’ve asked them to come back to me on the higher A/phase rated version - It’s probably overkill for what I need right now but no harm future proofing the build if I can

Click to expand...

I don't think it will be overkill as long as you are using a good battery.
And if it turns out to be, you can change the settings in the controller to lower the power a bit, upgrade the bottleneck component and then go full power later.

swiftyds said:

Thanks for the quick response and your other comments so far

Click to expand...

Glad I can help

swiftyds said:

Can you do me a favour when you have time - could you post up a couple of pictures of your motor fixings to the swingarm on your bike? I know I need to modify the rear of my swingarm and have seen how Manny did this on his RS50 conversion but would be good to see how this is mounted in a wider swingarm.

Click to expand...

Sure, but I don't think it will be very useful to you since I have a swingarm purposely made for a hub motor in the first place.
I'm using the standard QS motor plates, secured in place with the standard nuts, tightened very hard.

View attachment 2

This kind of stuff:



I think it should be included with your motor whenever you'll receive it.
It is ok for relatively low power, for instance it works fine on my bike because my controller has a relatively slow start. But it's not great when it comes to controllers who can deliver a lot of power instantly from standstill, in which case it cannot handle the power for very long and ends up being grinded by the axle.

This happened to one of my friends, we tried using those but they didn't hold and the motor started to rotate a bit inside the plates, so we had to design a clamp and attach the clamp to the swingarm. Here is how it looked like:



The front part with the two holes attached to previously existing holes in the swingarm, and the axle is sandwiched at the back between the two pieces, with two strong bolts. We machined that out of aluminum 7075 T6 aluminum.
It works very well and is able to handle the 50 000W we push to the motor during takeoff. You might want to do a similar system for your bike, it works well and its relatively easy to do even with basic tools.

Thanks for the pictures - yes I have to machine some plates anyway for fitting the motor to the Aprilia Swingarm. I’ve already sourced another swingarm that I will use off the bike to design the mounts.

I will check with Robert at QSMotor if the mounts come with it but as you say they probably won’t be of use anyway given my swingarm.

The motor is ordered and being manufactured now. Should be 3 - 4 weeks by the time it’s with me, in which time I need to source the battery.

Unfortunately the link you sent me is in US and they can’t ship outside of US so I’m still trying to find something suitable, most likely Lifepo4 still but not too heavy. The Valence packs are available to me in the UK but at 72v they would be 35kg. I know Li-on wouldn’t be that much lighter. I will keep looking as I can’t seem to find any Leaf cell pouches in the UK right now

swiftyds said:

Unfortunately the link you sent me is in US and they can’t ship outside of US so I’m still trying to find something suitable,

Click to expand...

Aw, that sucks.
Maybe you can check Aliexpress.
I just made a search real quick and found out that some vendors seem to propose these A123 cells, you can try and ask them if they can send you a complete pack (they probably can, send them a picture of what you want and take your time to explain clearly in simple, easy to understand words).
https://www.aliexpress.com/item/No-taxes-Original-A123-20Ah-3-2V-lifepo4-li-polymer-rechargeable-battery-A123-20000mAh-3-2V/32999041678.html?spm=2114.search0604.3.7.361b23efWKC9DJ&ws_ab_test=searchweb0_0,searchweb201602_6_10065_10068_319_10059_10884_317_10548_10887_10696_10192_321_322_10084_453_10083_454_10103_10618_10307_10301_10821_537_536,searchweb201603_80,ppcSwitch_0&algo_expid=f67f4bc7-4bf4-4072-bfde-80b7f4d900b6-1&algo_pvid=f67f4bc7-4bf4-4072-bfde-80b7f4d900b6

I purchase almost all my stuff on taobao, which is the chinese side of aliexpress and never had any problem, but I live in China so I don't know how this works out with UK.

You can also try to contact A123 directly, apparently they sell their 18650s on line, but maybe they can ship you a pouch pack if asked nicely
Here's the link:
http://a123batteries.com/

tighten those axle nuts until they snap off and then back off a quarter turn.
dont use and spring washers or whatever, jsut simple flat washers.

also put a witness blob on the axel and nut that cracks if the nut/axle moves. if you miss a moving axel you will mess up your axle and swing arm not to mention the phase wires.

I’ve gone back to look at the Valence Power u-Charge pack. These are LifePO4 cells with each module made up of 144 cells.

I can source 2 modules that are 38.4v/30AH each which in series would give me 76.8v / 30AH. The vendor tells me that the cells are rated at 10C and they have run a 20 minute test on the pack at 60A without any voltage drop/sag.

The size of the overall pack would be 35cm x 32cm x 20cm but as I posted earlier the weight is 34kg. I think I’m going to go with this pack at least for a starter as it will fit in the frame fine and I know these have been used in EV projects already. It’s also a decent price at < £500 with charger.

Any thoughts from folks here on whether you see any challenges here?

swiftyds said:

I’ve gone back to look at the Valence Power u-Charge pack. These are LifePO4 cells with each module made up of 144 cells.

I can source 2 modules that are 38.4v/30AH each which in series would give me 76.8v / 30AH. The vendor tells me that the cells are rated at 10C and they have run a 20 minute test on the pack at 60A without any voltage drop/sag.

The size of the overall pack would be 35cm x 32cm x 20cm but as I posted earlier the weight is 34kg. I think I’m going to go with this pack at least for a starter as it will fit in the frame fine and I know these have been used in EV projects already. It’s also a decent price at < £500 with charger.

Any thoughts from folks here on whether you see any challenges here?

Click to expand...

Probably too weak. I suggest you to keep digging, it's not like you're in a hurry to get the battery pack, you have plenty of other things to build first, this one can very well be the last.
So I'd recommend you to not rush and purchase unsuitable battery, keep your 500 pounds for something more worthy.
Just my advice after having a quick look at their specs, they don't seem to be able to deliver the required currents for long, so they might heat, and I don't really think serialed BMSs is a suitable solution for such high powers...

Ok but can you help me understand what it is with the spec given the cells are 10c and it’s been tested at 60a continuous for 20mins without any sag?

Also the BMS in the module is just for balancing on charging so I can use my own BMS or rely on the controller to limit voltage and display etc to monitor the battery packs when discharging.

I just want to get my head around what I should be looking for if this isn’t suitable and this is all good education for me.

Thanks

Thanks for all the feedback I’ve received which I’ve taken onboard and changed my controller and also revised the batter pack spec.

I’m sticking with the QSMotor 4000w v3 but switching the controller to a Sabvoton SVMC72150 / 150A battery amps with TFT display and bluetooth (the issue I missed on the Kelly KLS controller was that the Amp figures quoted were motor / phase amps). I’ve got contacts in the UK who are reliably running this controller on an Enduro Frame eBike set up using the QSMotor 205 3.5t hub motor at 150A battery power and achieving 90mph+ I know there are some comments out there about newer Sabvoton controllers being unreliable but everything I’ve seen on builders using them in the UK is that they’re proving reliable.

For the battery I’ve decided to invest in a new high power Lithium Ion pack using Samsung Q30 cells - 72v 40Ah with a smart BMS and which can put out 160A.It should give me a decent range at the average speeds I will be going, plus it will easily fit in the Aprilia frame and weighs less than 15kg. I’ve selected a UK builder for the pack at a very reasonable cost and they’ll provide a 12 month guarantee - the also guarantee genuine Samsung Q30 cells.

I’ve also sourced a new Aprilia RS50 swingarm to modify which will allow me to set the motor up off the bike, test everything then fit it to the bike.

Will include some pictures once all the parts start arriving