What's really required?

Technical discussion on converting internal combustion to electric
hipo_ev
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What's really required?

Post by hipo_ev »

Long time reader, first time poster - Hi :)

A few questions - sorry up front for silly questions.


I have a basic understanding of what I require, but what I do not know are the exact requirements (ie. amp ratings of contactors and fuses).

What I am looking to build is a hi performance EV (from a Subaru WRX), one that has at least equal performance to my 2002 Subaru WRX STi (ie. approx 0-100kmh in 6sec and 0-400m in 13sec) - I'm hoping for better then this, but this at a minimum would be an acceptable start.

My ICE car needs 200kw (~250kw at motor) to do this, but it would weigh more then the EV once finished, so I suspect at least 220kw would be required.

Some simple maths (excuse any mistakes - please correct for me if I am wrong):
w = a * v
w = 1400a * 144v
w = 224kw

So far, what I have on the list is:
48x Sky Energy 180aha lifepo5
48x Cell modules (balancers)
1x Netgain Warp11
1x Netgain Warp-Drive 160v 1400a controller
1x Warp-Drive interface
1x Warp-Drive water Ccooling kit (standard duty)
1x HETA throttle
1x Zivan NG3 charger
2x Inertia switch
1x Emergency stop button (low volt)
1x Brake booster vacuum kit
1x Power Steering kit
1x DC-DC

Now what I need to know is what rating contactor and fuses do I use? From what I can tell from other conversions, most use contactors and fuses that are rated quite low (200a-400a) - but would they be suitable for a high performance EV that will frequently draw higher then this under acceleration?

I have no idea what will be amps would be drawn to be honest, but if it is to run at least 13s 0-400m, then the contactors and fuses need to be able to support the current draw needed for at least 13 seconds.

AFAIK, the Sky Energy 180a cells are rated at 4c continuous discharge and 12c burst (10sec) discharge , which would equal 720a continuous and upto 2160a burst.

So considering White Zombie and other dedicated drag EVs are drawing most (if not more) of the rated amps available from their controllers (2000+), then would I also be able to draw the full 1400amps under acceleration (at least for 13 seconds) with the controller and battery pack I am considering?

All responses appreciated.

Thx.












Last edited by hipo_ev on Mon, 08 Feb 2010, 07:22, edited 1 time in total.
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woody
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Post by woody »

Hi HiPo,

Welcome!

I think you're onto a good thing with copying White Zombie.

Have a look at the White Zombie history page, work out which setup in the past gave him the performance you're looking for.

He's mostly had lead-acid batteries, but you're probably going to start with a heavier car than him which will make up the difference.

An imprezza is about 1300kg to start with, Datsun 1000s maybe 900kg?
Did you have a donor car in mind?

Another thing to consider is range - how far do you want to drive? If it's only 400m at a time, then Sky Energy may not be the answer - something with a higher C rating (20+) may be better - you can have a smaller pack and/or less voltage drop.

What are your other goals?

i.e. do you want to road register, carry passengers, air/con , AWD, go around corners fast?

The lighter the car you start with, the easier is to get quick, e.g. 70s datsun, corolla, escort.

Looks like fun :-)

cheers,
Woody
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack
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Post by hipo_ev »

Hi Woody,

Thanks for the quick reply mate :)

I originally got interested with EVs after seeing the Tesla several years ago and the performance it offers, and now after a couple of months of reading I now am ready to build an EV with similar performance - so I'd say the Tesla roadster is more of a benchmark to then White Zombie is.

However, the reason why I mention White Zombie is because it is more "real world" of an EV DIY then trying to reproduce a Tesla :)

Basically, the EV I make has to meet the following 5 criteria at a min:
0-100kmh in 6 seconds
0-400m in 13 seconds
100km per charge (standard driving conditions, one passenger)
Be road registerable
Seat 4 adults

Now obviously I doubt I'd get 100km of range per charge if I was constantly WOT, but that is the goal under standard driving (ie. daily commute)

The car I am looking at is a 1994-96 Subaru WRX, it has wet weight of approx 1230kg, is a 4door sedan, and has constant AWD. It comes with a 5speed manual, but I am considering swaping in a modified Subaru impreza auto gearbox - however I have not decided fully on transmission type and/or gearing.

I have seen this model WRX come down to close on 1000kg in race spec (all carpet etc removed) so I suspect that I should be able to come close to this with everything not needed removed (radiator, engine, gearbox, lots of wiring, ecu, exhaust, power steering unit, ac unit, etc) - my goal weight is 1100kg once complete.

The car will retain power steering and AC (for comfortable daily driving) but will not use the oem (read: heavy) pully driven units, instead they will be replaced with powered versions (as per my previous list).

I guess where my project halts, is with what rating contactors and fuses to use, and if I should use fuses, or mains-type circuit breakers. I just can't get my head around using 400a contactors if the EV will possibly draw 1400a!

Maybe there is someone in OZ (hopefully Adelaide) who has undertaken a more performance orientated EV build that you know of, which I could check out or look at the specs of their build?

Thx.





Last edited by hipo_ev on Mon, 08 Feb 2010, 10:08, edited 1 time in total.
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Post by EClubman »

Hi HiPo,

You will need better batteries and a bigger controller if you want to get those sorts of times with a car that heavy.

As a comparison, my car (650kg Clubman, Zilla 1K-LV, ADC 9", 156V Odyssey PC925 lead acid batts) has managed 16.8 in the 400.

Your car will weigh twice as much with only 40% more power - that says you will be slower down the track.

If you want to go fast, don't muck around. Get a Zilla 2K and some high power lithium batteries (A123, LifeBatt, Kokam etc).

Also, if you are dead set on the Imprezza, check out Cliff Rassweiler's car at www.proev.com - he uses two motors - one front and one rear.
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Post by lithbattboss »

If you want to build a high performance EV (plenty of power + long range) you certainly wouldn't choose a low performance lithium battery (less than 5C) eg, Thundersky, Sky Energy,etc. It just doesn't make sense!
You would use a very high discharge rate cell so you really only have two choices if you want to use LiFePO4. So your choice is either A123, or LiFeTech XPS Power cells.

Since you wanted a practical example you might like to check this Porche conversion done by Jeff McCabe-

http://www.evalbum.com/736

Check the performance figures using the old grey 40138cells which we discontinued a few months ago.
As a comparison our new X1P Power cells have 3 times the continuous discharge power rating of the grey cells used in this Porche.
The grey 40138 cells were rated at 10C compared to our new X1P Power cells which are rated at 30C continuous and 35C peak.

I am supplying cells locally for a Porche EV and possibly a couple of Subaru conversions shortly (both projects in Qld)so I will be pleased to publish the performance figures when these conversions are complete and on the road.

Of course you may want to choose LiPo so long as you take plenty of precautions due to the more hazardous nature of LiPo.

In the end it all comes down to dollars.
High performance A123 or LiFeTech batteries will cost far more than low rate Chinese lithium cells (in the same way that a high performance ICE sportscar (Ferrari,etc)will cost far more than your average family passenger car (Ford, Holden, etc)


Last edited by lithbattboss on Mon, 08 Feb 2010, 10:58, edited 1 time in total.
Where power matters.
XPS Power cells 25C discharge for high performance applicatiopns.
www.lifetechlithium.com
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Post by hipo_ev »

Hi EClubman,

Thanks for the reply. I originally considered the Zilla 2K, but I read they had a long waiting list (6 months?) whereas the Warp-Drive controllers were ready to be shipped. If I didn't have a budget, I'd go for a Kokam or A123 pack, but I am limited to $25k (ie. car has to be complete, drivable and registered for $30k - and this will have to includes the cost for the car and all EV components).

In your clubman, how many amps do you draw during a 0-400m run? Do you have a log?



Regarding your clubman's performance - first the motor:

You use a 9" motor, I will be using the Warp11, 11" motor, which offers much more torque. If we assume your ADC 9" has a similar output to the Impulse 9" your torque @ 1000a is around 233Nm, whereas the Warp11's torque @ 1400a is around 625Nm - almost triple the torque.



Second the battery pack:

From your battery specs, they are only 28ah, whereas the Sky Energy lifepo3's are 180ah.

From what I can find, your batteries are 925a for 5 seconds and then step down about 100a every 5 seconds, whereas the SE 180ah's can support 2160a for 10 seconds, after-which the safe draw is closer to 700a.

So even though your vehicle is lighter, your motor is only providing approx 1/3 the torque, and your battery pack would be providing less than 1/2 the amps to your controller that the same volt SE180ah pack could. Also, your batteries would be about 3/4 what your controller supports before 10 seconds had passed.


Saying that, from what I can tell, overall pack voltage is more important for 0-100kmh and 0-400m times - is this correct? Because if so, the Warp-Drive can be upgraded by firmware to 260v and even 360v as required.

This would then potentially support (simple maths, please correct if wrong):
w = a * v

160v
w = 1400a * 160v
w = 224kw

w = 1400a * 260v
w = 364kw

w = 1400a * 360v
w = 504kw

I'd however need to purchase the high voltage version of the Warp11, which "only" puts out 563Nm of torque at 1400a instead of 625Nm, as well as over double the amount of cells for my pack.


What do you think? I am running so many things through my head and don't won't to make the wrong choice.

Thx.







Edit: Lithbattboss, I understand what you are saying, but I am limited in budget as per my post above. Basically, the battery pack will have to cost <$15k AUD max to stay in budget (and that's pushing it).

I'm not after super high performance, just enough to do 0-100kmh in 6 seconds and 0-400m in at least 13 seconds.

If (for example) White Zombie could do 0-100kmh in 4 seconds and 0-400m in 13 seconds with a 11" motor and a 1200amp controller, with a Hawker Genesis 16ah SLA pack, then surely a lifepo3 pack offering higher burst discharge (over twice as much amps) and a continual discharge of 700amps running through a higher 1400a controller can support this (albeit I might need higher pack voltage)?

What would an equivalent 160v 180ah pack cost from you that could sustain a similar draw of 2000a for 10s and 700a continuous?



Last edited by hipo_ev on Mon, 08 Feb 2010, 11:52, edited 1 time in total.
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Post by antiscab »

hipo_ev wrote: Hi EClubman,

Thanks for the reply. I originally considered the Zilla 2K, but I read they had a long waiting list (6 months?)


welcome to the forum :)

I have a zilla 2k EHV here in Perth im selling if you are interested.

but im getting ahead of myself here :)

0-100 in 6, and 0-400 in 13 isn't possible for a conversion of that size with just $30k (the 0-400 will be the hard one)

sky energy cells do seem to be good for ~10C for 10sec, from the anecdotal reports ive seen (thundersky are good for around 7C)

~AUS$15k will get you a pack of 96 x SE 100Ah (307v nominal, 100Ah) 300kg
that will give you your range no worries.

max power at the batteries will be around 2.3*1000*96 = 220kw.
1000A@220v

the next thing is that without timing advance (which generally means your motor is too small) a warp 11HV is only good for 288v.

im tempted to use kostov data here, as they provide motor ratings closer to the sort of power we're after. the closer the real data is to where you need to extrapolate to, the more accurate it will be.

id suggest 2 x kostov R20

at 2000A motor side, each motor will give ~720Nm.

i suggest ditching the gear box, and driving each diff directly.

the setup would enter the power plateu when motor power in reaches 220kw. mech power out would be around 110kw (at big amps, motor efficiency sucks)

the setup would exit the power plateu when motor voltage reaches pack voltage.

shift the motors to parrallel, and the power plateu would then extend further out to around ~4300rpm, when each motor is seeing 220v and 500A.
torque at each motor is 180Nm.
power out for two motors combined is ~164kw mech for 220kw elec in.

what diff ratios do you have to choose from?

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
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Post by antiscab »

a better solution may be to put high rate cells (A123 or lifebatt) in parrallel with some sky energy cells.

that would save on weight, but not so much money.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
antiscab
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Post by antiscab »

more calculations:

0-100kmh in 6 sec for 1380kg needs ~89kw for the whole 6 sec, or linearly, ~177kw peak.
so thats entirely doable.

0-400M in 13 sec for 1380kg, would suggest power plateu starting at 45kmh (100kw mech) ending at 180kmh(164kw mech).

price list time?
zilla 2k: 6k
batteries + BMS 15k
charger 5k (32A at ~300v)
motors 5.5k
other stuff like labour, contactors etc 3k

abit over at 35k, but im sure theres stuff i missed.
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
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Post by antiscab »

hipo_ev wrote: AFAIK, the Sky Energy 180a cells are rated at 4c continuous discharge and 12c burst (10sec) discharge , which would equal 720a continuous and upto 2160a burst.


this bit stuck out,
the "continuous" 4C rating is actually for ~30sec.
the 12C rating is for ~10ms. (its more for determining max ripple from the controller)

although 7-10C can be pulled for ~10sec, this costs service life.
i don't know how much pulling big amps reduces service life though.


Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
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Post by Richo »

hipo_ev wrote: I'd however need to purchase the high voltage version of the Warp11, which "only" puts out 563Nm of torque at 1400a instead of 625Nm, as well as over double the amount of cells for my pack.


Would the WRX gearbox handle 563-625Nm?
So the short answer is NO but the long answer is YES.
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Post by hipo_ev »

Hi Matt,

Cheers for the info and reply :)
antiscab wrote:
0-100 in 6, and 0-400 in 13 isn't possible for a conversion of that size with just $30k (the 0-400 will be the hard one)
What calculations do you use to work this out?
antiscab wrote:
the next thing is that without timing advance (which generally means your motor is too small) a warp 11HV is only good for 288v.
The Warp11 HV comes with timing advance by default - is that what you mean? Regardless, they are still limited to 288v as you mention.

I can only afford to run a 160v setup atm, but wanted to go the HV (288v max) for options down the road (in case I needed to increase the pack voltage to achieve my performance and range goals).

I haven't really considered the Kostov motors, but will look into them over the next few days. Are they a better motor compared the the Warp11 HV - considering I'm only looking to run a 160v pack, and most likely only ever upto 240v if the budget 6-12months down the road.

I'm not sure if you have seen this info, but check out the bottom of THIS page, it lists torque at various amps - this is what I have been basing my current choice on.
antiscab wrote:
i suggest ditching the gear box, and driving each diff directly.
ATM my budget would only support a single motor - and since the Subaru car I want to use is constant AWD, the only way to take advantage of that AWD system with a single motor would be to utilise the transmission in the car. Also the other reason I was considering a transmission is for reverse (removes extra contactor complexity and costs for reversing the motor).

There is quite a bit of transmission support for the WRX (from it's rally and drag racing history), so I'm not too fused about using one as I can get a pretty beefy setup quite cheap. I guess the only thing I'd need to look at are gear ratios?
antiscab wrote:
the setup would enter the power plateu when motor power in reaches 220kw. mech power out would be around 110kw (at big amps, motor efficiency sucks)

the setup would exit the power plateu when motor voltage reaches pack voltage.

shift the motors to parrallel, and the power plateu would then extend further out to around ~4300rpm, when each motor is seeing 220v and 500A.
torque at each motor is 180Nm.
power out for two motors combined is ~164kw mech for 220kw elec in.
Not sure what you mean by power plateau. What is it exactly and how is it calculated?
antiscab wrote: what diff ratios do you have to choose from?

Quite a few, as before the WRX has quite a lot of aftermarket support, so I shouldn't have a problem finding an appropriate setup - what would you suggest as a decet ratio to start with for my performance goals?


antiscab wrote: more calculations:

0-100kmh in 6 sec for 1380kg needs ~89kw for the whole 6 sec, or linearly, ~177kw peak.
so thats entirely doable.

0-400M in 13 sec for 1380kg, would suggest power plateu starting at 45kmh (100kw mech) ending at 180kmh(164kw mech).
As above, what is meant by power plateau? Where can I find more info on that? Also, what calculation are you using to determine kw required to run 6sec?
antiscab wrote: price list time?
zilla 2k: 6k
batteries + BMS 15k
charger 5k (32A at ~300v)
motors 5.5k
other stuff like labour, contactors etc 3k

abit over at 35k, but im sure theres stuff i missed.

My current list:
$13,992.00 - 48x Sky Energy 180aha lifepo5
   $861.00 - 48x Cell modules (balancers)
   $250.00 - 48x buss bars
 $4,500.00 - 1x Netgain Warp11 HV
 $3,000.00 - 1x Netgain Warp-Drive 160v 1400a controller
   $350.00 - 1x Warp-Drive interface
   $350.00 - 1x Warp-Drive water Ccooling kit (performance)
   $550.00 - 1x Warp 11 forced air coooling kit
   $175.00 - 1x HETA throttle
   $115.00 - 1x Netgain speed sensor kit
 $1,855.00 - 1x Zivan NG3 charger
    $40.30 - 2x Inertia switch
    $11.00 - 1x Emergency stop button (low volt)
   $150.00 - 1x BEP heavy duty single pole battery switch (550a continuous, 2500a 15s max)
   $435.00 - 1x YT Stabletech vacuum kit
   $950.00 - 1x Power Steering kit
   $495.00 - 1x Power Steering kit
   $750.00 - cable, lugs, fuses, circuit breakers, connectors, etc
   $480.00 - 2x Gigavac GX14BCA 750v 500a contactors
    $75.00 - 1x Nanfeng contactor
------------------
$27,534.30 - total
------------------
I'm approx $2.5k over budget without a vehicle, but if that is everything, then I guess I will have to go over a little more to find a suitable car as well. Is that everything that is needed, or have I forgotten some things?

Also, as per my original question, I'm not sure about the last three things on the list - I'm totally stuck when it comes to what amp rating the contactor and fuses will need to be.

Cheers for taking the time to read through my posts :)

Thx.
Last edited by hipo_ev on Mon, 08 Feb 2010, 18:39, edited 1 time in total.
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Post by Richo »

hipo_ev wrote:
Is that everything that is needed, or have I forgotten some things?


Labour
Motor adaptor to gearbox
Motor frame to engine mounts.
Battery box
So the short answer is NO but the long answer is YES.
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Post by Richo »

1 x Gigavac won't do.
For 10sec they are rated to 710A.
Taking off from a standstill the current from the batteries will be low.
It will only be the top end when you draw the high current.
So even on a 6sec accelleration only 2-3 seconds will be at high current.

What are you using the nanfeng contactor for?

Since the batteries are 180Ah x 10C then this is 1800A.
For a fuse common sense would say somewhere between 1500-2000A.
But it depends on the fuse type as to how long before they blow at a given current.
The bussman fuses do go higher that what evworks generally stock.

This is why HV AC systems seem more feasable for high end power.
220kW@565V=390A
So the short answer is NO but the long answer is YES.
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Post by antiscab »

Hi hipo_ev,

hipo_ev wrote:
antiscab wrote:
the next thing is that without timing advance (which generally means your motor is too small) a warp 11HV is only good for 288v.
The Warp11 HV comes with timing advance by default - is that what you mean? Regardless, they are still limited to 288v as you mention.
the netgain HV motor uses interpoles, which means its stock timing is neutral for the 288v rating. if wanting to run more volts, this can be achieved by advancing the timing, but doing so reduces lower rpm performance.
hipo_ev wrote:
I can only afford to run a 160v setup atm, but wanted to go the HV (288v max) for options down the road (in case I needed to increase the pack voltage to achieve my performance and range goals).

I haven't really considered the Kostov motors, but will look into them over the next few days. Are they a better motor compared the the Warp11 HV - considering I'm only looking to run a 160v pack, and most likely only ever upto 240v if the budget 6-12months down the road.
if you can only afford a 160v setup, then id recommend getting a 160v motor to get the most out of the system (kostov do make 160v motors incidentally)

kostov having been using interpoles longer than other DC manufacturer that caters to the EV market.

White zombie originally ran a 11" kostov, until they fireballed the comutator.

running a motor with less than rated voltage lowers the rpm at which you reach maximum power point (and reduces power).

with a gearbox, this is less of an issue, but there are disadvantages to having a gearbox aswell.
hipo_ev wrote:
antiscab wrote:
i suggest ditching the gear box, and driving each diff directly.
ATM my budget would only support a single motor - and since the Subaru car I want to use is constant AWD, the only way to take advantage of that AWD system with a single motor would be to utilise the transmission in the car.
so the subaru system doesn't have independant diffs for front and rear?
i would have thought having constant awd would make ditching the gearbox easier....(i don't know subarus all that well tbh)
hipo_ev wrote:
Also the other reason I was considering a transmission is for reverse (removes extra contactor complexity and costs for reversing the motor).

There is quite a bit of transmission support for the WRX (from it's rally and drag racing history), so I'm not too fused about using one as I can get a pretty beefy setup quite cheap. I guess the only thing I'd need to look at are gear ratios?
best gear ratios depend upon the specific motor, and what controller and batteries you have.

if already keeping the transmission, then fair enough for using it for reverse (less resistance in the motorside connections)
hipo_ev wrote:
Not sure what you mean by power plateau. What is it exactly and how is it calculated?
a motor controller generally acts as a buck converter - that is - it steps down the pack voltage to the motor voltage effectively trading volts for amps.

so at stall (motor not spinning), motor side is say 10V 2000A, battery side is 200V 100A.
this is peak torque (assuming no timing advance trickery)

say you limit battery current to 1000A.

that means, when motor voltage reaches 100V (motor voltage increases with rpm) and motor current is still 2000A, battery side is 200V 1000A.

at this point, the controller starts operating in battery current limit, effectively limiting the power going to the motor.

this will continue until motor voltage reaches 200V.

since the controller can only step voltage down, this is the voltage limit.
when the motor spins faster, and the controller can't supply more volts, current (and thus power) falls.

this is the end of the power plateu.

once past the power plateu, power falls off rapidly.

id upload a picture, but the forums are on the fritz :(

the mech power at the end of the pwoer plateu in my example happens to be given to you by the motors performance graph, almost (192v, 500A, 72kw mech)

now that ive had a closer read of that motors specs, im less confident on the mech power at the start of the plateu.
at massive amps, i tend to just call the motor ~50% efficient, without other data.

i have other data now, so ill have another crack at it:
here is where the other data came from
139v 250A 3900rpm 30.3kw mech 4.45kw loss
160v 250A 4600rpm 35kw mech    5kw loss

this indicates between 0.8kw and 1.39kw of the loss at 3900rpm 250A is resistive.
the resistive component is the one that goes nuts when we crank the amps up.
at 2000A, this loss is 64x greater than at 250A.
so there is between 51kw and 89kw in resistive losses at 2000A.
still better than the 220kw in = 110kw out i suggested earlier.

the tricky thing is, series DC motors are harder to extrapolate, as their losses are more complicated. so you aren't going to know for sure what you have until *after* you have built it.
hipo_ev wrote:
antiscab wrote: what diff ratios do you have to choose from?

Quite a few, as before the WRX has quite a lot of aftermarket support, so I shouldn't have a problem finding an appropriate setup - what would you suggest as a decent ratio to start with for my performance goals?
for optimising 0-100 time, 100kmh = end of power plateu
for optimising 0-400M time, at 400M = end of power plateu.

the performance curve is different for every setup, but:

for the zilla 2k + 2 x kostov R20 + 96 x sky 100Ah setup i was talking about earlier:

400M: 180kmh = 4300rpm
205/50R16 wheels gives 1561.9 rpm at 180kmh
so optimal ratio is ~2.75:1

0-100: 100kmh = 4300rpm
20550R16 wheels gives 867.7rpm
so optimal ratio is 4.96:1
note: with that ratio, 0-100 is ~3.9sec, but 400M is like 17 sec.

with a gearbox you can have both, but if that means ditching a motor, all the power values are lower.
how much lower...ill get around to calculating when im more awake :)
hipo_ev wrote:
antiscab wrote: more calculations:

0-100kmh in 6 sec for 1380kg needs ~89kw for the whole 6 sec, or linearly, ~177kw peak.
so thats entirely doable.

0-400M in 13 sec for 1380kg, would suggest power plateu starting at 45kmh (100kw mech) ending at 180kmh(164kw mech).
*snip*
Also, what calculation are you using to determine kw required to run 6sec?
E = 1/2M*V^2
E/6 sec = ave power required.
since im assuming its linear, max power occurs at 100kmh, which is 2 x ave power.

i made an excel spreadsheet for coming up with this:
0_to_400_in_x_sec.xls

ill tidy it up a bit later, but for now those are the calculations.


hipo_ev wrote:
My current list:
$13,992.00 - 48x Sky Energy 180aha lifepo5
   $861.00 - 48x Cell modules (balancers)
   $250.00 - 48x buss bars
 $4,500.00 - 1x Netgain Warp11 HV
 $3,000.00 - 1x Netgain Warp-Drive 160v 1400a controller
   $350.00 - 1x Warp-Drive interface
   $350.00 - 1x Warp-Drive water Ccooling kit (performance)
   $550.00 - 1x Warp 11 forced air coooling kit
   $175.00 - 1x HETA throttle
   $115.00 - 1x Netgain speed sensor kit
 $1,855.00 - 1x Zivan NG3 charger
    $40.30 - 2x Inertia switch
    $11.00 - 1x Emergency stop button (low volt)
   $150.00 - 1x BEP heavy duty single pole battery switch (550a continuous, 2500a 15s max)
   $435.00 - 1x YT Stabletech vacuum kit
   $950.00 - 1x Power Steering kit
   $495.00 - 1x Power Steering kit
   $750.00 - cable, lugs, fuses, circuit breakers, connectors, etc
   $480.00 - 2x Gigavac GX14BCA 750v 500a contactors
    $75.00 - 1x Nanfeng contactor
------------------
$27,534.30 - total
------------------
I'm approx $2.5k over budget without a vehicle, but if that is everything, then I guess I will have to go over a little more to find a suitable car as well. Is that everything that is needed, or have I forgotten some things?


as stated earlier, you will need more contactors.
the gigavacs are probably fine for a 1400A controller, you may be struggling to keep the battery side above 1000A.

Matt
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Post by hipo_ev »

Richo wrote: Labour

own labour is free :)

And getting a few mates to help out here and there only costs beer and a bbq :p
Richo wrote: Motor adaptor to gearbox
Motor frame to engine mounts.
Battery box

I've got a mig, andenough tools to do the engine mounts and battery box, and a mate is an engineer and can do the adapter and any coupler I need at mates rates.

But yeah, I'll have to add this to the list though so I have a full picture of what's needed.
Richo wrote: 1 x Gigavac won't do.
For 10sec they are rated to 710A.
I've listed two of these - based on the specs I read, the GX14BC and GX14BCA are rated at 500a continuous and break at 2500a - would they not be suitable?

What would you suggest?
Richo wrote: Taking off from a standstill the current from the batteries will be low.
It will only be the top end when you draw the high current.
So even on a 6sec accelleration only 2-3 seconds will be at high current.
Ah, I always thought it was the other way around, and during take off from stand-still is when the most current is drawn. Cheers.
Richo wrote: What are you using the nanfeng contactor for?
Most EV schematics I have checked use a lower amp contactor before the DC-DC. Is it needed? I also saw one schematic with a contactor after the charger?
Richo wrote: Since the batteries are 180Ah x 10C then this is 1800A.
For a fuse common sense would say somewhere between 1500-2000A.
But it depends on the fuse type as to how long before they blow at a given current.
The bussman fuses do go higher that what evworks generally stock.
Ah ok thanks. I did look for higher rated fuses, but most of those even using Zilla 2Ks are using <1000a fuses? From what I gathered, I assumed they got a fuse to suit the max continuous current draw only - and not the max burst draw?

Thanks for the info Richo.
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Post by hipo_ev »

wow, thanks for all the info Matt - much appreciated.
antiscab wrote: if you can only afford a 160v setup, then id recommend getting a 160v motor to get the most out of the system
np. I initially was going to just go the standard warp11 and was only considering the HV because I wasn;t sure if I needed to go higher V to meet my performance goals.
antiscab wrote: White zombie originally ran a 11" kostov, until they fireballed the comutator.
I read about that and that is one of the main reasons I was thinking of going the Warp11 - the Warp11 is suppose to have a more robust commutator?

antiscab wrote: so the subaru system doesn't have independant diffs for front and rear?
i would have thought having constant awd would make ditching the gearbox easier....(i don't know subarus all that well tbh)
They have a rear diff, but I am pretty sure the front "diff" is actually part of the transmission.
antiscab wrote: best gear ratios depend upon the specific motor, and what controller and batteries you have.

if already keeping the transmission, then fair enough for using it for reverse (less resistance in the motorside connections)
ah ok np. I guess I won't know what to do with gear ratios etc until I have everything running and see what each gear feels like and go from there. I have read that some EV DIYers have had all but 3rd and 4th gear removed from their EV - in the WRX I can get dog gears for 3rd & 4th pretty cheap, so I could leave out 1st & 2nd and choose suitable 3rd & 4th gear ratios once I know what each gear feels like.
antiscab wrote: a motor controller generally acts as a buck converter - that is - it steps down the pack voltage to the motor voltage effectively trading volts for amps.

so at stall (motor not spinning), motor side is say 10V 2000A, battery side is 200V 100A.
this is peak torque (assuming no timing advance trickery)

say you limit battery current to 1000A.

that means, when motor voltage reaches 100V (motor voltage increases with rpm) and motor current is still 2000A, battery side is 200V 1000A.

at this point, the controller starts operating in battery current limit, effectively limiting the power going to the motor.

this will continue until motor voltage reaches 200V.

since the controller can only step voltage down, this is the voltage limit.
when the motor spins faster, and the controller can't supply more volts, current (and thus power) falls.

this is the end of the power plateu.

once past the power plateu, power falls off rapidly.

id upload a picture, but the forums are on the fritz :(

the mech power at the end of the pwoer plateu in my example happens to be given to you by the motors performance graph, almost (192v, 500A, 72kw mech)
Thanks for explaining that :)
antiscab wrote: i have other data now, so ill have another crack at it:
here is where the other data came from
139v 250A 3900rpm 30.3kw mech 4.45kw loss
160v 250A 4600rpm 35kw mech    5kw loss

this indicates between 0.8kw and 1.39kw of the loss at 3900rpm 250A is resistive.
the resistive component is the one that goes nuts when we crank the amps up.
at 2000A, this loss is 64x greater than at 250A.
so there is between 51kw and 89kw in resistive losses at 2000A.
still better than the 220kw in = 110kw out i suggested earlier.

the tricky thing is, series DC motors are harder to extrapolate, as their losses are more complicated. so you aren't going to know for sure what you have until *after* you have built it.
Yeah I suspected that. All I have been doing is looking at other builds with the warp11 and hoping my performance will be similar. There are a few I have seen that can do 0-100kmh in 6-7 seconds, but none list 0-400m. Most of these though, use SLA battery packs of around 144v-160v.

antiscab wrote: for optimising 0-100 time, 100kmh = end of power plateu
for optimising 0-400M time, at 400M = end of power plateu.

the performance curve is different for every setup, but:

for the zilla 2k + 2 x kostov R20 + 96 x sky 100Ah setup i was talking about earlier:

400M: 180kmh = 4300rpm
205/50R16 wheels gives 1561.9 rpm at 180kmh
so optimal ratio is ~2.75:1

0-100: 100kmh = 4300rpm
20550R16 wheels gives 867.7rpm
so optimal ratio is 4.96:1
note: with that ratio, 0-100 is ~3.9sec, but 400M is like 17 sec.

with a gearbox you can have both, but if that means ditching a motor, all the power values are lower.
how much lower...ill get around to calculating when im more awake :)
lol, thanks for taking the time - I didn't mean to keep you awake :)

How did you calculate what speed equals what rpm?

A stock 94-96 WRX has 205/50/16 wheels, with a final diff ratio of 4.444, however this can be changed if required.

So 4.444 would be good for 0-100kmh, but would be poor for 0-400m - I assume that is only in direct drive?

TBH, when it comes time to work on gear and diff ratios, I'll be back in here anyhoo :p
antiscab wrote:
E = 1/2M*V^2
E/6 sec = ave power required.
since im assuming its linear, max power occurs at 100kmh, which is 2 x ave power.

i made an excel spreadsheet for coming up with this:
0_to_400_in_x_sec.xls

ill tidy it up a bit later, but for now those are the calculations.
Cheers for the link - I'm sure it will be very helpful :)

antiscab wrote:
as stated earlier, you will need more contactors.
the gigavacs are probably fine for a 1400A controller, you may be struggling to keep the battery side above 1000A.

Matt

I thought I would, any ideas on what I could use that won't blowout my budget too much?

I noticed some ppl either run 2x contactors in series for failsafe, but I also noticed that some put a smaller contactor in series in the middle of their battery pack - what is the best method for wiring in a separate contactor for failsafe?

Cheers again for all the info guys.

Thx.
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Post by Richo »

hipo_ev wrote:
Richo wrote: What are you using the nanfeng contactor for?
Most EV schematics I have checked use a lower amp contactor before the DC-DC. Is it needed? I also saw one schematic with a contactor after the charger?

The contactor isolates the traction pack.
A second contactor seems redundant.
Some DC-DC have a voltage free contacts that just need shorting together to turn on.
So a small 12V relay would be fine for these.
It really depends on the DC-DC.
hipo_ev wrote:
Richo wrote: Since the batteries are 180Ah x 10C then this is 1800A.
For a fuse common sense would say somewhere between 1500-2000A.
But it depends on the fuse type as to how long before they blow at a given current.
The bussman fuses do go higher that what evworks generally stock.
Ah ok thanks. I did look for higher rated fuses, but most of those even using Zilla 2Ks are using <1000a fuses? From what I gathered, I assumed they got a fuse to suit the max continuous current draw only - and not the max burst draw?

More calcs on manf data would be needed if this is the case.


edit: fix typos
Last edited by Richo on Tue, 09 Feb 2010, 05:10, edited 1 time in total.
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Post by Richo »

I have started a new thread on fuse selection as it's really it's own topic
Fuse selection thread
So the short answer is NO but the long answer is YES.
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Post by antiscab »

hipo_ev wrote:
antiscab wrote: White zombie originally ran a 11" kostov, until they fireballed the comutator.
I read about that and that is one of the main reasons I was thinking of going the Warp11 - the Warp11 is suppose to have a more robust commutator?
the warp11 does have bigger brushes (IIRC) than the kostov 11.
FWI, the kostov failed in white zombie partly because they were running higher than rated voltage (like 300v into a 192v rated motor).

hipo_ev wrote: lol, thanks for taking the time - I didn't mean to keep you awake :)
im a night worker who is frequently awake at odd hours due to caffeine :p
hipo_ev wrote:
How did you calculate what speed equals what rpm?

A stock 94-96 WRX has 205/50/16 wheels, with a final diff ratio of 4.444, however this can be changed if required.

So 4.444 would be good for 0-100kmh, but would be poor for 0-400m - I assume that is only in direct drive?
take wheel size: xxx/yy/zz
circumference = (xxx*yy*2/100 + zz*25.4)/1000 M
rpm at wheel = (kmh/3.6)*60/circumference

yes that would only be direct drive.

if using a transmission, i would make "gear 1" 1:1 (since the diff ratio is already good for 0-100), and "gear 2" ~2:1.
antiscab wrote:
as stated earlier, you will need more contactors.
the gigavacs are probably fine for a 1400A controller, you may be struggling to keep the battery side above 1000A.

Matt

I thought I would, any ideas on what I could use that won't blowout my budget too much?

I noticed some ppl either run 2x contactors in series for failsafe, but I also noticed that some put a smaller contactor in series in the middle of their battery pack - what is the best method for wiring in a separate contactor for failsafe?

[/quote]

the contactors that break the circuit when bad things happen need to heavy *really* high break current ratings, so are naturally bigger.

all the contactors in the circuit must be able to conduct the RMS current for full charge of the battery pack.

since the middle contactor doesn't have to switch under load, it can be smaller.

the middle contactor is included (actually there should be more than one middle contactor) is there to break the pack up into smaller voltages.

calculated power and accleration for 1400A controller, 48x se 180Ah, warp 11:

max battery power is ~1400A@120v = 168kw (controller limited)

torque at 1400A will be greater than 565Nm (although the motor is in saturation, increasing current will still increase torque by a greater amount since both fields are getting stronger).

gotta break out my graphics calculator to work out more :)


Matt
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Post by antiscab »

back to calculating motor output:

so at 0rpm, you have a bit over 565Nm (1400A motor side)

72v 452A 1442 rpm 182.25Nm becomes 148.8v 452A 2980rpm 182.25Nm
at ~2980rpm you have 182.25Nm (148.8v 452A motor and battery side, controller operating "full on")

at 1400A battery voltage will be around 120v.
using the 72v 452A 1442rpm data point:
12-v 452A ~2400rpm.
since when operating full on, reducing speed to half, increases torque 4 fold.
so 565/185.25 = 3.1x
sqrt(3.1) = 1.76
2400/1.76 = ~1363rpm
max power point would be around ~1363rpm a bit over 565Nm(1400A 120v motor and battery side)

the result here is worse than in the kostov example because it is low voltage and controller limited.

low voltage means that a great proportion of the voltage going to the motor is lost to resistance.

controller limited means the battery is only utilised to its full potential when the motor is at max power point.

0-100 and 0-400 to follow.

Matt
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Post by antiscab »

actually, come to think of it, the resistance component of votlage drop doesn't increase when you increase rpm (at least not by a significant amount).

so assuming half the losses at 72v 452A 1442rpm 185.25Nm is resistance, that means the votlage drop is ~5v.
that means at 148.8v:
143.8/67 = 2.14xrpm
3094rpm 182.25Nm 148.8v 452A.

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Post by hipo_ev »

Thanks for the calculations Matt, very much appreciated - I have another question for you now :)

I was readying about WZ and how it has dual motors and his Zilla can switch from parallel to series to improve hp. Is this possible to reproduce using a single motor but switching the traction pack from parallel to series?

Just say, for example, that 64 SE130 cells were used in total. And you had two banks each with 32 cells in series and then used the Zilla to flip the contacts to switch from parallel to series during acceleration at a specific RPM, would that improve performance and acceleration the same as though you were switching dual motors from parallel to series?

In the scenario I describe, with a single motor, the following is for the traction pack.

All cells in series:
64x SE130
217.6V nominal
130A C1
520A C4 max continuous

2x 32cells in parallel:
2x 32x SE130
108.8V nominal
260A C1
1040A C4 max continuous

That works out be $13,516.80 just for the cells and approx $4,800.00 for a HV Warp 11.

Or would it be better, performance wise, to just use that same money to buy dual 9" motors and cells? The Kostov Dual R20 9" motors are around the same price as a single HV Warp 11, so it would cost the same either way.

This is with the SE130 cells, obviously performance would be better if I was to use A123 cells or similar. But since my budget is limited, and I am trying to keep total cell cost down <$15K (including BMS) I can only afford to buy either 45 SE180 cells, or 64 SE130 cells (and this is what gave me this idea to run parallel and series).

Saying that, I could even go 84 SE100 cells if that would improve things even more, but I'd have to split into 3P and suspect that, even though total available A is increased, the lower voltage this provides would not be worth it.

ie:
All cells in series:
84x SE100
285.6V nominal
100A C1
400A C4 max continuous

3x 28cells in parallel:
3x 28x SE100
95.2V nominal
300A C1
1200A C4 max continuous

I thought it might also be worth mentioning the weight difference between the different traction pack options (cells only, not including misc parts and holders):
84x SE100 = ~260kg pack weight
64x SE130 = ~282kg pack weight
45x SE130 = ~252kg pack weight

Anyhoo, just thinking out aloud and was wondering if it is not even worth the hassle.
Last edited by hipo_ev on Thu, 04 Mar 2010, 10:31, edited 1 time in total.
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Post by Electrocycle »

whether the cells are in series or parallel their total KW output is the same.
The controllers can't switch cells between series and parallel (as it would change the input voltage) and there would be no benefit - since it can already convert volts to amps for high current low rpm use.

The series / parallel switching with motors means you can spread out the power band - to maintain power over over a wider rpm range.
It won't improve your peak hp, but it will improve your average hp as long as the batteries can keep up.
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Post by antiscab »

hipo_ev wrote: I was readying about WZ and how it has dual motors and his Zilla can switch from parallel to series to improve hp. Is this possible to reproduce using a single motor but switching the traction pack from parallel to series?
Series/parrallel switching is used where the motor controller isn't large enough.

take two motors, for example.
each can take 288v 1000A (peak)
but your controller is 288v 1000A.
and your batteries can only put out 1000A at 288v.

if you put them in series, the controller can apply full current, but only half voltage.
if you put them in parallel, the controller can apply full voltage, but only half current.

the batteries can only supply half the max power for the two motors anyway.

so you start in series, and switch to parrallel to get the best of both worlds.

if you originally started out with a 288v 2000A controller, than series/parallel shifting doesn't help you.

switching the batteries around won't help in this regard (at least not my a significant amount).

in both cases, go for high voltage traction battery. it gives you better options controller wise.

if you have say 100 x 100Ah cells,
the battery would be good for ~600A @ 250v.
if you combined that with a HV zilla 1k, then you could run *any* motor, since the controller can buck the volts to amps for lower voltage motors, or apply full voltage for higher voltage motors.

if you went with 45 x 180Ah cells,
the battery would be good for 1080A @ 112.5v
The controller can trade volts for amps, but not the other way round. so that would limit you to low voltage motors, so only the warps, or ADC, etc.
hipo_ev wrote: Or would it be better, performance wise, to just use that same money to buy dual 9" motors and cells? The Kostov Dual R20 9" motors are around the same price as a single HV Warp 11, so it would cost the same either way.
im more inclined to use the kostov motors, as they give more performance information. theres only rumours to go off for the HV warp 11.

aside from that, i don't know which would be better, due to the aformentioned lack of data.

Matt
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