Question for Aussie Matt

Gday Simon,

atm, when i limit my discharge to 30AH, i get 40km at 60-70kmh. (range doesnt seem to vary alot, as better conditions tend to result in a higher top speed rather than more range).
the cells have experienced some capacity loss of around 3AH (around 10%) over this time (though this is based on a bench test of one cell that was operating far enough below the rest of the pack, the BMS wouldnt let me charge).
i might be able to get more information on this when i get a bench tester that is capable of 50-100A, unlike my current one which only does 20A.

the end of discharge voltage also falls, so i now limit my discharge depth to 30AH.
i have reinstalled my paktrakr, so on the next long range run i can see if its just one cell whose capacity has fallen, or a number of them.
my usual twice daily rides are between 15-20km (which sees 10-20AH drawn from the pack).
so i dont have to use the scooters full range very often

after 15'000km, everything is still going as it should.
ive recently re-installed my paktrakr, so im getting some per-cell data-logging now.
every 4-5000km i have to balance the pack again, as one cell (and it always seems to be a different one) goes out of balance. This requires a 60v, 0.5A powersupply overnight. not a huge problem.
the cause of this problem is my charger float stage voltage is quite high enough to do 15cells (its off by maybe 0.2v)
rods BMS modules need above 3.6vpc before they start to balance.

the hub motor is rated to 1500w at i assume to be 60kmh.
i currently feed it around 2500w continuous, and have been doing so for the past 13'500km (since i went to 19cells, 57v under load).
i have changed the current limit on the controller to 125A, so i get a peak of near 6000w under acceleration - i highly recommend this mod to anyone. this mod is only effective at speeds under 50kmh, above which im limited by pack voltage.

acceleration wise, going to 6000w is about the best thing ive ever one.
top speed wise, i should have used 20cells to get the full 70kmh.
if you need full 45mph, id suggest getting 21cells or more.

im still using the original emax controller. the only thing i have done to it is solder a bit of copper wire across the internal shunts to raise the current limit.
in theory i should have changed the ripple caps to higher voltage ones, but the original ones are surviving fine.

the cells do a whole lot better when its hot i must add.
when temperatures are down around 20 deg c, i see 2.8-2.9vpc at 40A.
now that temperatures are up around 35 deg c, im seeing 3.1vpc at 55A.

the motor does run hot at the higher than rated loading, but it hasnt failed yet. PJD has a motor thats loaded just as hard, and has done more miles than i have, his hasnt failed either as far as i know.

as far as how heavy is the scooter...i cant say, i havent ever measured it.
it does however feel much lighter, and the centre of gravity is much lower. as a result it is now much easier to move around.

the scooters evalbum page is: http://www.evalbum.com/1499

hope this is helpful,

Matt

PS. are converting an emax aswell, or another scooter?

Hi,

glad to hear you found a use for the Paktrakr.

I included it in the design of the Vectux M-BMS but could not afford to buy it at this stage.

Maybe later. Do you know if the Paktrakr could be connected "remotely", to long hippie-cables connected to the cells via 15kOhm resistors and 20Aa fuses? That would make it easy to retro-fit it to the Vectux.

Gday Mik,

yeh, i was a bit disappointed to have to shelve a $500 piece of equipment, so im happy to put it back into service.

i highly recommend putting a switch inbetween the batteries and first wire of each sub-module of the paktrakr if you do ever get around to installing one.

im not sure how the paktrakr modules would respond to high resistance between the modules and cells.
each module pulls 3ma from the first 5v worth of cells (so 5 cells for nimh, or 2 cells for Lithium) to power itself.
and the module with the paktrakr head unit pulls 9ma. so for those cells, the measurement would definately be stuffed up.

im guessing you are asking this because you dont look forward to pulling your vectrix apart again?
the wire runs between the modules and the batteries, and the paktrakr head unit are quite long to start with.

is the reason for the 20A fuses so you can perform balancing on those wire runs?
if not, i would ditch the resistor, and use say 0.25A fuses. (if a short occurs, these should interrupt the current without literally exploding, as long as you use thin wire).

Matt

Hi Simon,

how much range are you after?
two 1500w motors would probably run more efficiently than my single one.
the other reason my energy usage is somewhat above average is that i ride throttle wide open *all* the time.
at what speed are you intending to ride at?
what range are you after?

the bms units on my bike are the orignal ones. they are bulky, and were hand made by rod in his workshop.
these old units added 25mm to the height of the cell.
the new units are very small (they dont rise above the terminals, so height isn't increased) and are mass manufactured.

the reason i mount the cells upright has more to do with battery box geometry than anything else.
as far as i know, if you mount the cells with any of the smaller sides to the ground, the cell will work fine
if you lay them flat, im less sure how they would fare.
i know of only one application where the cells are layed flat:
http://photos.evahakansson.se/#home

its a relatively new bike conversion, so any cell deterioration wouldnt be evident yet.
you could also join the thundersky yahoo group, and ask a bloke named victor (i forget his last name).
Victor has been using thundersky cells basically since the "beginning".

another suggestion with TS cells is to mount the cells with pressure plates on the end of each string of cells.
mine dont have this, so i would be interested to see how much these improve performance.

the DC-DC i use is original with my emax. the only other way to do it on a scooter with hub motors is to use a separate 12v battery.
you could try and find out from the xm3500li guys what dc-dc is on their bike, since they run 60v.
the emax dc-dc is only rated to 48v.

Matt

im not sure how the paktrakr modules would respond to high resistance between the modules and cells.
each module pulls 3ma from the first 5v worth of cells (so 5 cells for nimh, or 2 cells for Lithium) to power itself.

That would be a problem. I designed the Manual BMS (M-BMS) for the Vectux in such a way that it is safe for me and others, like the original Vectrix is. You need a lot of tools and time to get to the parts which carry dangerous voltages and currents, or a major accident, like a truck running over the battery compartment.
The 15kOhm resistors (in line with the fuses and the rest of each tab) are limiting the maximum current that will flow at maximum battery charge level to less than lethal currents - that is below 10mA.
150v / 1500Ohm = 10mA. (Usually there would be 2 resistors = 30kOhm, one on each cable, but just to be sure to be sure...)

I would be dead now if I had not put the resistors in, because I got a little electric shock the other day, from right to left hand, across the heart, with about 136V, but current limited by the resistors. The shock was a lot weaker than what you get when touching a cattle fence, but it was quite clearly there. At that limited current level you would probably be able to control muscle action = let go of the live part, even if a piece of wire made really good contact by piercing the skin, or touching an open wound, like on an inured EV scooter rider lying in a puddle under his bike....

The problem in relation to the PakTrakr: 5V / 15kOhm = 0.333333mA and would not be enough for the PakTrakr.

im guessing you are asking this because you dont look forward to pulling your vectrix apart again?

You bet!

is the reason for the 20A fuses so you can perform balancing on those wire runs?

Yes, once someone invents something that can do it. The cables are over-sized for currently available technology!

if not, i would ditch the resistor, and use say 0.25A fuses. (if a short occurs, these should interrupt the current without literally exploding, as long as you use thin wire).

Matt

I do not really understand what you man with that, sorry...

I want a balance between the ability of individual cells to open the fuses if shorted, and maximum current carrying capacity for balancing and for reconditioning or testing of cells without having to remove them from the pack. A low current rating fuse will introduce a lot of measurement error during charging or discharging / reconditioning through the M-BMS.

If needed later on, I could connect the Pakrakr to the cell tabs inside the battery housing. Because the tabs are already installed now it would be relatively easy.

Hi Simon,

if you *need* 60km, id suggest designing for 100km.
if you *need* 80kmh, design for 90kmh.

whether 60 or 72v would be better depends on the hub motor you choose.

the aerodynamic nature of the vehicle has a far greater effect on range than weight does (unless of course your destination is uphill from your current location).

where are you located?
if you are in perth, i can lend you 9x 12v 20AH agm batteries, so you can work out real world energy usage.
that way you have a better idea of how much battery you would use.
if you are in other parts of Australia, then i can put you in touch with someone who can lend you batteries.

Matt

having just read through another of your threads,

i see you are in Tasmania.
Ill ask around.

btw, are you a member of the AEVA?

Matt

if the short circuit current is above the interrupt current rating of a fuse, the blown fuse may arc, and not break the circuit, or if it does break the circuit, it may explode and destroy things around it.
automotive blade style fuses are particularly bad, since they are only intended for low voltage.

this type of failure mode is far more prevalent in higher value fuses.

re the paktrakr, unfortunately i dont really see a way around this.
you may have to pull the vectrix apart again to install the paktrakr.
the upside is the paktrakr modules also record temperature.

Matt

Hi Simon,

it seems our presence is all that great in Tas:
http://www.aeva.asn.au/forums/forum_posts.asp?TID=737

only two members.
the AEVA is the Australian Electric vehicle association.
basically the aim is to put all the EV ppl in Australia in touch with each other.
comes in handy when you need to borrow tools and odds and ends.

sounds like a ufn project you have on your hands.
are you affiliated with any kind of college or university over there?
what kind of grant are you getting? very interested to hear the outcome of this.

id be happy to show you my electric vehicles when youre next in WA.
hopefully my mr2 will be finnished then.

Matt

good effort with the grant...i would never have thought of the arts community as a place to get a grant.

a fellow postal worker, awesome.
i work in parcel sorting here in Perth.

yeh those honda ct110 will definately be hard to top.
theyve only been in production for 20 years. :p

i wonder if you will need a motorbike licence to ride your creation?
over here we're really short on posties, so much so now we're hiring people to do the rounds on push bikes.

Matt

you need the width in the motor to get a high enough torque.
so no, they wouldn't be modifiable.

you might have a hard time finding a thinner motor with enough power.
perhaps a pancake motor might be more what you are looking for?

Matt