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EV Conversions


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dyrodium
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EV Conversions

Since moving to perth I've been giving EV's some serious thought, with the roads being dead flat - driving every day only about 15-20min each way and petrol fluctuating to 1.65/L every 5 seconds... and I've inherited what I think is the perfect donor car for converting...

So, questions aimed at Dumhed and Glen mostly, but Brett you probably have a great deal of knowledge too Smile

How much outlay should I expect for a basic conversion? 10K? I would need a range of ~30k each day.

Vehicle is a diahatsu move - plan would be to remove the back seats to create a battery tray.


What are good cells to go for these days now A123 is gone? Headway seem OK.

Motors - series DC, burshless, what options ? The car weighs sfa but I'd love to be able to troll the crap out of all the wankers in Perth.

What then needs to be done to get it roadworthy and such...

Just trying to sus out if it's worth the bother. Would be fun tho. Laughing
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Post Fri Jul 25, 2014 12:14 pm 
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Glen
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Depends on how much battery you need but the price of the cells means it will never make much sense financially. Shouldn't be too hard to EV swap that if you just want to throw money at a project Laughing

Something like the CALB cells would be good imho. You need too many individual headway cells which makes balancing/bms and rework a major pain in the butt.

Big series wound or DC motor would be the budget options. Others use Vector controlling VFDs on AC motors, but getting rather pricey and complicated there.

Gotta have an electric demister, power steering pump and air con/heater setup if you want to keep that. Otherwise engineer has to sign off on the work done.
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Post Fri Jul 25, 2014 12:34 pm 
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DumHed
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a lot of the Australian EV people are in Perth - so I would be pretty tempted to keep an eye out for second hand gear, unfinished projects, or even complete cars.
They come up for sale pretty often and will save you a huge amount of time and money.

Check out the AEVA forums (http://aeva.asn.au/)

and EV Works (http://www.evworks.com.au/)
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Post Fri Jul 25, 2014 12:53 pm 
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Knightrous
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There is a wicked little Toyota Sera that was converted to electric in Perth.

Build thread here: http://www.toymods.org.au/forums/engine-driveline-conversions/46573-no-pistons-no-fuel-no-worries-toyota-sera-ev-conversion-begins%85-print.html

He would be probably the best bloke to chat to as he went through the whole engineering and rego process which included covering air conditioning and electric power steering.

50FWHP of winning.

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Post Fri Jul 25, 2014 2:40 pm 
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Valen
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For EV's the battery cost roughly works out at buying your next 10 years worth of fuel up front. (if you include the cost of electricity as well) at least last time I checked.

The key "figure of merit" is the watt hours per mile/per kilometer from there you can work out how much battery you need.
if you assume 250wh/mile or 155wh/km you can work out the battery size.

so roughly
30km *155 = 4650 watt hours.
make it 5000 for a bit of margin

so if you hit up
http://www.ev-power.com.au/-Sky-Energy-Batteries-.html you can see the cells
say 60 ah

60ah*3.2v = 192 watt hours per cell
5000/192 = 26 cells
which is also 83 volts which is nice.

http://ev-power.com.au/webstore/index.php/12v-lifepo4-batteries/calb-lifepo4-cells/ca60fi.html
for a ballpark price of $94 per cell
so about $2400 on batteries.

then you need BMS $14 each + the monitor call it $800

charger nfi

speed controller

drive motor

some sort of heating for the front demister

$$$ for engineering certs.


Your 10K budget sounds like its in the right ballpark, but yeah see if you can get into the community over there, they will be able to show you the engineers who have done it before which should make things much easier.

in terms of "go" you get 6C from that pack which is 83v(pack) * 60(ah) * 6(c) = 30 Kw
so not that super awesome

if you go headway you get 20c pulse (in theory) but Andrew and Glen would know more in practice.

15Ah * 3.2v = 48Wh/cell so you need 104 cells. (presumably you would arrange them to get something in the 80v out range for a dc motor, though 300v means you could go ac induction)

332.8v * 15ah * 20c = 99840
or call it 100kw or 133 horsepower
that'd do the job at least off the line for the princely sum of $3120
http://ev-power.com.au/webstore/index.php/12v-lifepo4-batteries/hw-lifepo4-cells/headway-40160s-15ah-cell.html


Now strictly for the giggles
http://www.hobbyking.com/hobbyking/store/__14609__Turnigy_nano_tech_5000mah_10S_25_50C_Lipo_Pack.html

36 volts per pack, 5ah = 180wh per pack
so 28 packs or $3360 (though you may get a discount)
1008 volts (one would presumably run some in parallel lol) * 5ah *50c = 252000
so 252kw or 336 horsepower.

That would be suitable for blowing the doors of pretty much anything on the road if you could get the power down.

It will increase the cost for your traction motor and speed controller "just a touch" and the cell life probably won't be as good, (by like 8 years) but still, it'd be fun right?
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Post Sat Jul 26, 2014 11:03 am 
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Spockie-Tech
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Jakes comment about "buying the fuel up-front " is a good summary of E.V.'s

We used to say the same thing with Electric Heli's vs Nitro Heli's.

The Nitro motors are cheaper than equivalent powered Brushless+ESC+Battery+Charger combo, but you pay a lot more for fuel each time you run the motor, whereas the Electricity to recharge your batteries is much cheaper.

For accurate TCO (Total Cost of Ownership) comparison, You also need to take into account lifetime/deterioration and repairs and maintenaince/consumables (oil, plugs, and filters) of your combustion motor (and its many auxillary systems, cooling, exhaust etc) on one hand,

and the same of your The EV systems. Which mostly dont suffer anywhere near as much deterioration/consumables as a combustion motor system. Mishaps discounted, your Motor, ESC and Charging systems dont deteriorate at any appreciable rate and dont require any consumables.

Of course, the eternal phrase - Batteries not included. They *do suffer deterioration and require eventual replacement.

So, your EV costs all come down to what you choose to use battery wise.
Which is determined by your expectations of performance and range.

If you have a small lightweight car and you are happy with a top speed of 70/80 km/hr (wind resistance increases dramatically at high speed increasing power consumption) with modest acceleration and only need to commute <50km to work and can recharge during the day, then you can get away with relatively cheap and heavy (so a small kw/hr pack) lead acid batteries.

Effectively what you have is what is called a N.E.V. (Neighbourhood Electric Vehicle) which will get you to the shops and work and back, which covers about 90% of most peoples travel requirements. and is largely inefficient travelling (lots of slow, idling, repeated accel/decel time, in traffic)

If you want to head off on an interstate trip, tow a trailer, or load up the family for a day trip to the nearest city/beach/mountain, then you fire up the Dino-Juice burner and use a vehicle that is designed for sustained high power/load travelling and isnt spending most of its time chugging away at the lights doing nothing useful.

If you want to combine both functions in the one vehicle, then you are looking at large lithium (or maybe NiMH) battery packs, bigger motors, gruntier speed controllers and faster higher current chargers and the cost starts spiralling upwards.

One cheap work around is to put an auxillary battery pack in a trailer you keep at home when doing N.E.V. work, and just hook up when you need longer range on occasion allowing you to cart a smaller battery pack for ordinary use.

You can save some dollars building your own ESC from the open source plans available out there, and a simple cheat used by some on a budget is to use a contactor that engages for full-power, bypassing the ESC altogether and allowing you to use a lower rated ESC for part throttle operation but still giving you full power for climbing hills.

If you are looking for professionalism of course, just buy a 'Zilla or supposedly the Kellys have improved a fair bit these days.

Depending on useage patterns, you can register the Dino-burner on limited-use "Club" registration and insurance, which lets you use it a couple of times a week and pay full reg for the EV. Thus not have to pay two lots of full reg/insurance for owning a NEV and a Fuel-Burner.

OR you can just shell out the $$ and buy the latest Tesla Model S.
http://theoatmeal.com/comics/tesla_model_s

That option isnt likely to appeal to a Robot Builder though Smile
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Post Sat Jul 26, 2014 4:24 pm 
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dyrodium
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Ahh this is why I love this community so much, you guys are such a wealth of knowledge. Razz

Very true, it is a bit naive to approach EV's from a 'saving money' angle, not gonna happen. However really I'm keen to do it for the trolling factor of the vehicle, and the fun of a big EV project.

Haha running with hobbykring cells... Considering a Lipo EV is a driving bomb, I think I'll pass .... >_>

I really don't think SLA will cut it for the performance I'd be after, it's only a small car and it'll be weighed down hugely. 3K ish for batteries is do-able.

Very cool to hear that Perf has a big EV community, will hit that up. Very Happy
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Post Sun Jul 27, 2014 12:20 pm 
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Spockie-Tech
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quote:
Originally posted by dyrodium:
Ahh this is why I love this community so much, you guys are such a wealth of knowledge. Razz



Opinions anyway, considering that none us has actually built road-registered EV's (possibly DumHed ?),
I dont know that Id call it *knowledge* Smile


quote:

> Very true, it is a bit naive to approach EV's from a 'saving money' angle, not gonna happen.



It *can, you just have to take the long view and design carefully, The deck is stacked against lone builders, because they are doing difficult, unique custom one-offs which require skilled engineers rather than just factory assemblers and you're buying gear in any significant quantity to attract bulk discounts, unlike manufacturers, who buy in 10k lots.


quote:

Haha running with hobbykring cells... Considering a Lipo EV is a driving bomb, I think I'll pass .... >_>



Whereas a big tank of liquid petrol is.. what ? we're just *used to that Smile


quote:
I really don't think SLA will cut it for the performance I'd be after, it's only a small car



Which is why SLA *is an option. Unless you define performance to equal long range + high speed + high load.

Remember - The Peukert Value is the thing to consider when sizing batteries. SLA's can do OK, provided you dont try to discharge them too quickly.. (Robot Wars and our 3 minute matches are about the nastiest thing you can do to an SLA Smile ) Most are rated at a 20 hr discharge. Design a car and pack combo that eats them up in 1 hour and you are wasting a lot of capacity to internal heat. (you could use them as your demister ! Wink )

If you size the pack and motor power consumption appropriately, then given their low purchase and replacement cost and lack of BMS (Battery Management System) requirements, they can be a good choice for a low powered lightweight NEV. Ive read of quite a few of them that perform quite well on a pack that cost less than $1k, instead of upwards of $3k, so dont write them off to get started, unless you have plenty of money to play with and want to go for the newest expensive tech straight off the bat.

Lithiums *are undoubtably better, but they are more fragile, require BMS, trickier chargers, a *lot more expensive, and have unproven lifetimes at this time. (AFAIK). so whether they will prove to be better for 2 or 3 years, then down to 50% and please-replace-me status only time will tell.

What I would like to see is the new Low-Self-Discharge (LSD) Nickel Metal Hydride Technology (Sayno EneLoop) scaled up to EV cell size. Surely that pesky Ovonics Patent has expired by now ?

Take a look at White-Zombie from Plasma Boy Racing - http://www.plasmaboyracing.com/whitezombie.php
He ran SLAs for a long time in his drag Car and did remarkably well because he matched the pack size to the current draw properly. He eventually upgraded to lithiums, but it cost him 5x as much to go 1 second faster.

I plan on Electrifying the Ge-Min-E as my next Automotive project once the Charger is finished. (getting close !), so I keep half an eye on interesting developments in the EV scene. Be keen to see how you go.

Good Luck
regards
Brett
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Post Sun Jul 27, 2014 4:13 pm 
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Jaemus
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Another thought, considering that tin can Diahatsu is probably only about 1% safer than a motorcycle, have you considered doing a motorcycle? I suspect a cheaper overall conversion and total cost, probably not much less range since it all scales down reasonably (but not completely) linearly.

This is of course exactly what Dumhed did so I'm sure he can offer some advice there
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Post Sun Jul 27, 2014 9:46 pm 
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DumHed
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yeah it's pretty cheap to do a bike compared to a car, but it's a lot less practical as a day to day vehicle.


I wouldn't bother with SLAs at all - they tend to have a life span of 6 months to 2 years - so lithium actually works out cheaper in the long run, as well as giving *much* better performance.

My old bike, which was fully road registered and pretty practical for my use at the time, had a $230 battery pack - but it had fairly low performance and about 15k's max range.
I don't think the battery would last much longer than a year either - it was working pretty hard.

My second bike - which has never been road registered but is being used as a bit of a test bed, currently has a ~$1500 battery pack, but easily pulls wheelies and should have a range of 60-80km.

here's the info on my old bike: http://www.evalbum.com/1492
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Post Mon Jul 28, 2014 8:47 am 
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Spockie-Tech
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quote:
Originally posted by DumHed:

I wouldn't bother with SLAs at all - they tend to have a life span of 6 months to 2 years - so lithium actually works out cheaper in the long run, as well as giving *much* better performance.



OK, Good Point Smile

There *are SLA's that will do fairly well in an EV, Being Deep-cycle rated, and if you can limit them to <80% Depth of Discharge (DOD) and not run them nearly flat, they will last 5+ years, but such batteries do tend to be more expensive that your garden variety SLA's, so probably the margin over the getting-cheaper Lithiums is closing.

but keep in mind I havent seen any evidence of hard-worked Lithium Packs lasting more than 2 or 3 years yet either, and the replacement cost is higher.

Anyway, if $10k for a conversion doesnt scare you off, then its probably a moot point, youre up in lithium land with that kind of price ticket anyway.

Im still hoping something will appear with the Patent Expiry on large format NiMH batteries soon too. they are proven long life, less violent that lithium, much cheaper and offer fairly good power/weight/price ratios.
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Post Mon Jul 28, 2014 12:02 pm 
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Valen
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watch out for the range calcs on bikes, the reports of the wh/km out of them seem to put them into the lower range of cars.
(kinda the same as fuel really, a good fuel efficient car is similar to a bike on fuel consumption)

Regarding the fire aspect, having seen a few car fires in the wild I sure as crap would rather sit next to a lipo cell cooking off inside its nice steel box vented to outside than having burning fuel running under the car ;-> so really it'd be calendar and cycle life that would dissuade me from lipo power.

Andrew what sort of wh/km were you getting on your bike? I was looking at making a "cruiser" for cassie but the batteries really killed it.
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Post Mon Jul 28, 2014 3:28 pm 
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DumHed
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I don't remember - but I think from power point to road was something like 140wh/km

Charge efficiency was horrible on the SLAs though.
I think people have gotten down under 100wh/km but as you say - they are comparable with a small car if you're doing any sort of speed.
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Post Tue Jul 29, 2014 10:50 am 
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