Planning Scooter Conversion

Technical discussion on converting internal combustion to electric
Post Reply
Pumba
Noobie
Posts: 8
Joined: Thu, 22 Aug 2013, 21:23
Real Name: Olly
Location: Canberra

Planning Scooter Conversion

Post by Pumba » Thu, 22 Aug 2013, 23:32

Hi everyone, hoping for a bit of advice on my first conversion: an electric Vespa.

I'm an electrical engineering student, so have a small amount of knowledge, and am eager to learn more. Eventually I'd like to convert a car, but I figure starting with a scooter might be a good stepping stone, while I gain some knowledge, and money Image

I've already got the Vespa, just in the process of registering then selling the motor.
Image

I'm in the planning stage, trying to figure out what will work best, will probably drop the money for the parts in about 6 months.

I've seen Soyachips Vespa conversion on this forum and have gotten some good ideas from it, however for my conversion I'd like to use a hub motor, for simplicity, and it will leave maximum room for batteries. I plan on having two equally sized battery packs under each cowl of the Vespa for equal weight distribution, and putting the other components under the seat with the gas tank removed.

Here's an initial selection of the main parts:
6KW 72v 10" hub motor
200A Kelly Controller
Headway 15ah cells
MiniBMS (not really sure about this, suggestions?)

I've calculated I can fit about 60-70 Headway cells maximum under the cowls total (a bit more than 30 under each), but will do more precise measurements soon. This leaves me with 2 options: 1) Run 24S2P giving me 72v 30ah (2.1kwh), or 2) Run 32S2P giving 96v 30ah (2.9kwh). The motor is specified for 72v, but I can only fit in the above to battery configureations, and I think option 1 might limit my range a bit (I'm hoping for over 50km).

My main question is would it be ok to run this motor at 96v instead of 72v? Will I get increased performance? There's a performance graph on the website, but it's a little confusing. I would also like to be able to achieve highway speeds (110km/h) for a short period, so was thinking the higher voltage might help with that.

Also does any one know whether ACT or NSW is easier to get a conversion registered, or are they all pretty much the same? I'll need to make a new swing-arm for the motor so I'm assuming I need an engineer certificate.

Thanks!






User avatar
jonescg
Senior Member
Posts: 2149
Joined: Thu, 21 Jan 2010, 23:05
Real Name: Chris Jones
Location: Perth, WA.

Planning Scooter Conversion

Post by jonescg » Thu, 22 Aug 2013, 23:48

How much do you want to spend? What kind of over-spend are you willing to accept? Use this number to temper the other numbers Image

Was the scooter always able to do 110 km/h? I think you might find those speeds a bit unsteady, and very hungry on the amp-hours. My gut feeling is to keep the motor within it's limits at first, but design your machine so it may be easily upgraded later on.

You will need an engineers certificate for any conversion, and they will inspect the motor mount and swingarm as part of that.

AEVA National Secretary, WA branch vice-chair

User avatar
Bluefang
Groupie
Posts: 90
Joined: Wed, 13 May 2009, 22:37
Real Name: Derek Hohmann
Location: Gold Coast, Queensland

Planning Scooter Conversion

Post by Bluefang » Fri, 23 Aug 2013, 02:05

Be careful with changing the swing arm and rear brakes as it may mean you will have to get a brake test done on the bike. If you want to lower the financial burden you could always try having a look at http://www.endless-sphere.com/forums/vi ... 31&t=40859 and the other motors John has. I have used one as a mid drive on a bike at 130+V and can say it delivers the power I am also using his bigger 13" motor from the same manufacture on a motorbike, but with either of the 10" motors I think you will struggle abit at 110km/h

That will be extremely scary at 110km/h but good luck either way

User avatar
Johny
Senior Member
Posts: 3672
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Planning Scooter Conversion

Post by Johny » Fri, 23 Aug 2013, 02:58

Hi Olly and welcome to the forum.
Pumba wrote:My main question is would it be ok to run this motor at 96v instead of 72v? Will I get increased performance?
The controller is the limiting device for voltage and I see the Kelly you chose is rated at 120 V so it will be fine. I doubt that 96V will hurt the motor but you can always keep it within limits with the controller.

Not sure what the question is about a BMS but you should definitely have one. Headway sell a 16 cell BMS and while they have had a chequered past, the 12 BMSs I run have all been (and are still) fine. For 2P 15AH cells you will need at least the 180mA bypass current that their BMS provides to balance them in a reasonable time.

Pumba
Noobie
Posts: 8
Joined: Thu, 22 Aug 2013, 21:23
Real Name: Olly
Location: Canberra

Planning Scooter Conversion

Post by Pumba » Fri, 23 Aug 2013, 04:11

Thanks for replying everyone :) I'd like to spend about $6000 on electric parts, but anything under is a bonus if it's possible. How much does the registration cost? I've heard engineer certificates are about $1000?
The scooter currently has a top speed of about 100km/h. It has 8" wheels, but after the conversion they will both be 10" (a fairly common conversion for extra stability). I wont be doing highway speeds for long, I understand it will chew through my battery, just want it to be available as there are a few highways around (probably only for 1km distance).

Thanks for the motor suggestion Bluefang, haven't seen that one before, looks interesting. It will be a city scooter, but I would like the option of highway speeds for a short period if possible.

That's good to know about the motor, just wanted to make sure I wasn't going to be putting in lots of extra energy, and for it all to just come out as heat! I emailed Kelly, and they said that the continuous current rating is about 80A, and peak is about 150A. Will this be any different at 96v? Will it be less efficient?

I don't know what my question about the BMS is really either, just wondering if anyone had any recommendation. I've looked at the Headway ones before. One thing that worried me was that they say they have a maximum current rating of around 80A. While I probably wont be using more than that anyway, my battery pack will be capable of 300A peak, and 160A continuous, and if I ever want to transfer the parts to another project I wouldn't want the BMS to be the limiting factor.

So do these components seem adequate for my budget and needs?


User avatar
Johny
Senior Member
Posts: 3672
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Planning Scooter Conversion

Post by Johny » Fri, 23 Aug 2013, 15:25

Pumba wrote:I've looked at the Headway ones before. One thing that worried me was that they say they have a maximum current rating of around 80A.
You can order just about any current rating - they just change/add the shunts on the BMS. I actually don't use the current limit on my BMSs - I use them for low/high cell voltage monitoring and balancing. I rewired my packs to bypass the current limit shunt (and the pack cut-out). Since you are doing your own it would be easy just not to use the current limit in the BMS - whatever brand you decide to use. You would, however, have to provide a signal from the BMS(s) to alert that there was a problem (cell low/high).
So do these components seem adequate for my budget and needs
To be honest I can't make much sense of the motor curves but they appear to indicate that speeds in excess of 100km/h won't be a problem.

Can anyone comment - is 67NM at the wheel adequate for a Vespa style scootor?

Pumba
Noobie
Posts: 8
Joined: Thu, 22 Aug 2013, 21:23
Real Name: Olly
Location: Canberra

Planning Scooter Conversion

Post by Pumba » Sat, 24 Aug 2013, 05:36

Johny wrote: You can order just about any current rating - they just change/add the shunts on the BMS.
Ah ok, it seemed weird to me they wouldn't make a bms that can handle their own batteries power!

antiscab
Senior Member
Posts: 2181
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Planning Scooter Conversion

Post by antiscab » Sun, 25 Aug 2013, 03:07

Would go for a bigger kelly than 200A - remember you can back it off in software if it is too much

The other thing to watch out for is starting current is usually lower as the controller will be operating in "discontinuous conduction mode". having a bigger controller will mean starting torque is closer to the peak torque for a given motor current limit.

overvolting the motor is fine, it will bump up your top speed

it takes about 7kw to do 100kmh continuous

i don't see a charger listed, but these are probably the best bang for your buck:
http://ev-power.com.au/webstore/index.p ... w-pfc.html
http://ev-power.com.au/webstore/index.p ... w-pfc.html

other voltages avail as special order from tc charger

BMS:
I would use a BMS that can disconnect a charger on high voltage.
you can power the kelly controller logic side via a bms, to the bms never has to deal with high current

67Nm is a bit gutless, but that's only at 125A. 400A I would expect to be ~130Nm (not 3x due to saturation effects)

Vectrix wheel torque is (rated at) 390Nm (peaks at 70kmh), for reference, but that weighs 340kg with rider......

I suggest using a main fuse sized to your traction wiring (150A would be a good size, with 25mmsq wire) and at least an accessories fuse that's somewhat smaller (5A is usually plenty for 96v)
http://www.evworks.com.au/index.php?category=13

for traction wire you could also use 5 x 6sqmm wire - its cheaper and easier to deal with.

shame you can't cram more battery under that seat :(

Matt
Matt
2011 Blade Electron mk6
2007 vectrix - 145'000km
1998 Prius - needs batt
1999 Prius - needs batt

User avatar
jonescg
Senior Member
Posts: 2149
Joined: Thu, 21 Jan 2010, 23:05
Real Name: Chris Jones
Location: Perth, WA.

Planning Scooter Conversion

Post by jonescg » Sun, 25 Aug 2013, 04:36

I can recommend some great cells, but they are rather expensive. Depends on what you want out of the bike though.

I'm still a little disturbed that scooter did 100 km/h Image
AEVA National Secretary, WA branch vice-chair

Pumba
Noobie
Posts: 8
Joined: Thu, 22 Aug 2013, 21:23
Real Name: Olly
Location: Canberra

Planning Scooter Conversion

Post by Pumba » Sun, 25 Aug 2013, 06:32

Thanks for all the advice antiscab! A lot of good information.

Will that controller limit acceleration? It should be good for 200A continuous and 400A peak, while the motor will only take 150 A peak.

I'm looking at miniBMS, Batrium, and headway-headquarters BMS's, I think they are capable of shutting off the charger, but will keep that in mind.

More batteries would be good, it seems space is the limiting factor for motorbike/scooter conversions. I might be able to fit 64 A123 20ah pouch cells, which would increase range by 25% (3.8KWh vs 2.8KWh).

Pumba
Noobie
Posts: 8
Joined: Thu, 22 Aug 2013, 21:23
Real Name: Olly
Location: Canberra

Planning Scooter Conversion

Post by Pumba » Sun, 25 Aug 2013, 06:37

jonescg wrote: I can recommend some great cells, but they are rather expensive. Depends on what you want out of the bike though.

I'm still a little disturbed that scooter did 100 km/h Image


Which cells are they? I think Headway or A123 should be more than enough, the motor wont be able to handle all the current they can provide Image

The vespa has an upgraded px150 engine that puts out about 10Hp, it's quite scary popping wheelies at lights!

User avatar
jonescg
Senior Member
Posts: 2149
Joined: Thu, 21 Jan 2010, 23:05
Real Name: Chris Jones
Location: Perth, WA.

Planning Scooter Conversion

Post by jonescg » Sun, 25 Aug 2013, 06:48

EIG make a Lithium-NMC pouch cell which has superior energy density and respectable discharge rates. If range is your cup of tea, these would be the ideal cell. The same number of kWh would only occupy half of the volume of Headways and weigh about 40% less. See our sale thread in the Parts/Vendors section. They work out to be about twice the price of CALBs though.

You'd still be able to pop (controlled) wheelies at the lights Image
AEVA National Secretary, WA branch vice-chair

antiscab
Senior Member
Posts: 2181
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Planning Scooter Conversion

Post by antiscab » Sun, 25 Aug 2013, 08:38

Pumba wrote: Will that controller limit acceleration? It should be good for 200A continuous and 400A peak, while the motor will only take 150 A peak.


you won't know if it will limit it till you build it, but 400A should be enough (i had read 200A in the original post which gave me cause for concern)

the peak current of the motor would be limited more by demag of the magnets i would suppose

for what it's worth I ran the "1500W" 48v motor on my old emax at 400A motor current (battery current went as high as 260A) with a kelly 400A 72v controller.

Although that motor did eventually eat it's hall sensors, that was more likely due to the continuous power being too high (it got too hot - 1500W motor being run at 3000W continuous)

in short, in terms of short term power output, the motor can go much further than 150A. I would suggest the actual short term limit is somewhat higher than 400A

it's the continuous output you need to be more concerned with

Matt
Matt
2011 Blade Electron mk6
2007 vectrix - 145'000km
1998 Prius - needs batt
1999 Prius - needs batt

Pumba
Noobie
Posts: 8
Joined: Thu, 22 Aug 2013, 21:23
Real Name: Olly
Location: Canberra

Planning Scooter Conversion

Post by Pumba » Tue, 27 Aug 2013, 17:09

jonescg wrote: EIG make a Lithium-NMC pouch cell which has superior energy density and respectable discharge rates.
Hadn't heard of them before, but they are impressive! Also quite hard to find a retailer, and expensive! Think I'll stick with Headway or A123, unless I manage to increase my budget dramatically Image

Pumba
Noobie
Posts: 8
Joined: Thu, 22 Aug 2013, 21:23
Real Name: Olly
Location: Canberra

Planning Scooter Conversion

Post by Pumba » Tue, 27 Aug 2013, 17:23

antiscab wrote:in short, in terms of short term power output, the motor can go much further than 150A. I would suggest the actual short term limit is somewhat higher than 400A

it's the continuous output you need to be more concerned with
Matt

Thanks, I'll bump up the controller to something slightly bigger. Is there a way to limit the continuous current to the motor in the controller programming? Or do I just have to be careful not to floor it for too long?


I'm considering buying my batteries from BMS Battery, as they seem the cheapest (for Headway at least) and have a reasonable reputation from what I can tell. I've also seen some very cheap cells (Headyway and A123) on Alibaba. Has any had any experience buying such cheap cells? I certainly wouldn't buy any large number without doing thourough testing of a few, and even then it would be a gamble as to their quality, just wondering if anyone has any experience.

Thanks

User avatar
Johny
Senior Member
Posts: 3672
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Planning Scooter Conversion

Post by Johny » Tue, 27 Aug 2013, 18:08

I located Headway on Alibaba and dealt directly with them.
I would be wary of buying cells any cheaper than BMS Battery - they appear sell for less than Headway already. I've shied away from BMS Battery in the past due to their high shipping rates but I've not wanted any quantity I guess.

User avatar
Richo
Senior Member
Posts: 3189
Joined: Mon, 16 Jun 2008, 00:19
Real Name: Richard
Location: Perth, WA

Planning Scooter Conversion

Post by Richo » Tue, 27 Aug 2013, 20:49

By the time you get them shipped, pay duties and taxes and exchange rate I doubt it would be cheaper than what ev power claims to sell them for.
http://ev-power.com.au/webstore/index.p ... -cell.html
Help prevent road rage - get outta my way! Blasphemy is a swear word. Magnetic North is a south Pole.

User avatar
Johny
Senior Member
Posts: 3672
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Planning Scooter Conversion

Post by Johny » Tue, 27 Aug 2013, 21:31

Excellent point Richo. I hadn't realised that EV Power sold them.
BMS Battery want $1529 for 64 cells and $427 is the minimum price for shipping on that order (I just dummied it up). That's $1956.
EV Power's price is $29.75/cell which is $1904. Shipping can't be that much more.

User avatar
Johny
Senior Member
Posts: 3672
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Planning Scooter Conversion

Post by Johny » Tue, 27 Aug 2013, 21:33

...and that is NOT including duty etc and the port fees as it's over $1000 so customs takes notice.

Pumba
Noobie
Posts: 8
Joined: Thu, 22 Aug 2013, 21:23
Real Name: Olly
Location: Canberra

Planning Scooter Conversion

Post by Pumba » Wed, 28 Aug 2013, 00:51

Good point about the extra fees, I'll have to look into that a bit more. When I try to buy cells from ev-power, it says the maximum allowed is 4? Maybe they're out of stock now.
Looks like you can get Headway 15ah cells for 20AU on alibaba ($1300 for 64 cells), plus shipping and taxes. Might be able to get them to say their value is under 1k for customs... heard it's a fairly common thing for them to do

Thanks for everyone's help, I'm feeling more confidant about the build, can't wait to get it started!

Post Reply