Ah! now you're talking. I was wondering what those strange "kg" figures were all about

Hey, welcome to the forum. That's an interesting project you have there. However, I can't find a battery cell to match your power & weight requirements. Did you select a cell brand/model yet?

JR

 

I was reading somewhere... let me find it. Basically not your standard LiFePO4 but rather Lithium-polymer or LiPos. Many websites list these as having wh/kg above 130, some as high as 180 (those are too expensive, at $1.30/wh). To get into my target weight for batteries I am looking for 3.7V 100AH LiPos with at least 130 wh/kg. I have only started looking for them today so I have not found anything yet. I have seen other members talking about LiPo on this site so maybe they will know where to get them.

I would run 110 cells at 3.7v for a pack voltage of 407 @ 100 AH. My peak power draw will draw about 1-2C (depending on motor), with cruising being around 0.3C. Should be within the guidelines for those batteries.

 

Hmmm recovering waste heat alone won't cut it for GTA weather there won't be sufficient BTUs to safely operate the car here and keep in mind that you are required to have the vehicle inspected and meet standards in order to register it as a EV plus don't forget the clockwork OPP safety blitz

While a big direct drive high torque AC motor would be nice don't discount a smaller motor & reduction gearbox just yet and perhaps consider a smaller battery pack for around town and a towable BP for those extended trips up the 400 and beyond.

 

I will also be installing heated seat covers - they don't use too much power and they really help in cold weather.

I know about the inspection but isn't it as simple as just getting a mechanic to review the car and verify that the brakes/lights work, and that the car is physically sound?

I want to fit everything internally, however I will most likely make a system to allow me to easily lift out some of the batteries when I am just cruising around town. The problem with smaller DC motors is that they are usually air cooled. When I am cruising I will be using around 14-15KW of power, and even if the motor and controller are 90% efficient at converting that to mechanical motion I will still be getting 1500W of heat to dump into the cabin for free!

Also, AFAIK larger motors are more efficient because they are running at a smaller % of their maximum power? A 60kw motor will have less loss running at 15KW than a 30kw running at 15? Also, I'd like to have a little bit of power in this machine....

 

The MOT won't care about heated seats specifically your defrosting system must be functional at all times and that means all windows must remain clear while operating the vehicle.You certainly won't have the required heat on a cold frosty morning or during extended stop & go driving, you can do a topic search for more info.
The inspection won't be as simple as bringing in a factory car but you need to consult the certified mechanic that will handle the inspection for details, the car will be treated as a modified vehicle, floor & structural modifications, battery, inverter & motor mounting, wiring, ride height etc will be inspected plus you need to look at anything that may place any EMS person in danger while responding to a vehicle accident.

What specific motor/inverter are you considering?

 

Hmm this discussion remnds me of my threads

http://www.diyelectriccar.com/forums/showthread.php?t=62916

on recycling the motor heat from say - an ac50/curtis combo

...and on making a really long range vehicle

http://www.diyelectriccar.com/forums/showthread.php?t=62916

My idea for going long was starting with an aerodynamic coupe with a smallish frontal area, and putting batteries in place of the small bench seats. Accepting a heavier & longer vehicle (which is only going to hold 2 people like a SMART!) means less town range but on highway where wind resistance counts ... could do ok.

Bear in mind it's all theorycrafting - listen to the guys who actually have have built stuff before you listen to me.

The 4 seater requirement makes things harder. I guess that means stuffing batteries under the hood, and in the trunk.

You're also planning to use higher energy battery chemistry than iron phosphate. Bear in mind you are putting these cells in the crumple zone, you need to research here and make sure these alternative chemistries still possess sufficient safety.

You know this 4 seater thing reminds me of the situation with laptops - on some models, you could slot an additional battery into the DVD drive bay to get a longer runtime.

If only there was some way to do the same with our EVs... slot additional batteries in to the trunk or rear seats when we're making a long journey.

Airliners have to make tradeoffs too, they can't take off with full tanks AND full pax AND full cargo holds.

 

I am definitely okay with having to put an extra battery pack in the back seat to make the longer trips. I will only need the 4 seat capacity on short trips.

I think that I will run a 240V pack voltage, using 80AH 3.7V cells. I will put 65 of these cells into the car, and have a second battery pack with another set of 80AH 240V that be installed in the back seat for long runs. (parallel or series? better to boost the pack voltage to 480V?)

This will give me 20kWh pack normally, and a 40kWh pack in extended range mode.

EDIT: Also, there are other ways to prevent frost from forming.... Frost only forms if you have warm, humid air inside the car, as the water will condense on the cold windshield and freeze. If the air inside the car is also cold/dry it will be hard for frost to form. I can drive the car with the air inside being 5C with a heated seat, sweater and heated steering wheel.

 

If you want maximum range, don't forget overall system efficiency. You want to use the most efficient motor and controller you can find.

Up to 30% of the battery's power can be wasted as heat through the motor, controller, contacts, and cables.

Voltage is important too. Although it really won't make much of a difference with the motor's overall efficiency, it helps a little. And it can make a big difference in the controller's efficiency by cutting down on current. Your cables will also run much cooler. And if you increase the voltage to the point where it cuts the current in half, you can use much thinner cables, which saves weight as well.

 

I want to go high voltage, but I don't want to make the car too dangerous! Is their a problem with using extremely high voltages such as 800VDC?

If I can find the right batteries I will try and have two packs at 400V/50AH each, and so the question is, serial or parallel? 800V is a LOT of voltage, but if I could handle it safely it would mean only drawing around 15 Amps at cruising speed and 50A at acceleration (when only 1 pack is installed double the current, but that's still only 2C peak).

As for efficiency, I figure I should be able to have a VERY efficient drive train by using a belt-driven direct drive? With a ratio of 4:1 it would be right around perfect, leaving me with 5,000 RPM at 90 km/hr (56 mph)

 

Oh my. That's a lot of volts.

When I recommended high voltage, I was referring to 240 or 480 instead of 120. If you are pulling 200 amps at 120V, you will drop down to 100 amps at 240V and 50 amps at 480V... which is nothing for 2 gauge wire to handle.

I think 800V would be a tad bit too much. On the flip side, you can probably wire the batteries together with 10 gauge wire

There are several problems with that much voltage. First of all, you will need totally enclosed components (which is not a big deal anymore... everyone makes them). Secondly, capacitors are hard to come by at that voltage, which makes building a controller hard.

The EP-1000 controller that I have is available for up to 450 volts, but that's because the capacitors don't come too much bigger than that (not that you can fit inside the control box, anyways).

I would keep it at 480 max for any setup (except for maybe an AC motor). Plus, it makes charging so much easier, because 480 volts is available in most commercial locations in the USA. This will allow you to charge with a transformerless onboard charger, which weighs next to nothing. Just make sure everything is double insulated

 

Okay, I will keep the voltage below 480V. How will I keep the two packs of batteries evenly charged when running them in parallel? Considering that the pack permanently installed into the car will get much more use, how will I level out both packs to be even when I go to install the second one for longer trips?

 

You can't really, which is why it's a bad idea. Keeping all the cells in use all the time helps them age equally and it lessens the load on the cells by spreading it out over a larger pack. Shallow cycling the cells is the best way to prolong their life. There is no point in buying all that battery capacity and leaving half of it sitting on the shelf most of the time.
As for higher voltage, accessories become harder to find and more expensive as your pack voltage increases. Chargers, DC/DC converters, heaters, etc.

 

Do you think that I could fit all 300kg of battery in the car without having any protrude into passenger space? I would really like to be able to take other people with me in the car.

I thought I would remove some to make a more efficient ride, but I guess the charge balancing issue would be too much. Maybe if I made a switch, and then halfway through my journey I pull in for a snack at tim hortons and flip a breaker, switching power from one pack to the other.

I just can't see fitting 100 x 3.7V 200AH cells into a tercel's trunk/hood. I suppose if I get really creative I might be able to do it. Anyone here have experience with putting a lot of batteries into a small car?

 

I don't think the 200 ah LiPo cells you are talking about even exist. Even if they do, 100 cells at 200 ah's gives you a larger pack than a Tesla, which can do over 200 miles.
Also, spending the kind of money you are talking about on a Tercel doesn't seem to make a lot of sense.

 

Oops, sorry. I meant 100AH.

37kWh pack.

What would be a good modern body to do this with? I don't want to spend too much on the donor car, but I want it to last a long time. I am also looking for a very low drag coefficient car, the 1999 4Door Tercel has 0.32!

Also, the idea with the budget is to spend as much as a nice ICE car would cost, and get a really nice result. This would be my only car, and I want it to last for 5+ years of light driving (with the occasional road trip). Is there a place to get a new glider? That would absolutely perfect I think. It's just too bad the ontario government no longer hands out it's incentive for conversions... $8k in pocket would have been useful to say the least!

 

.32 seems about average, you can do better. http://en.wikipedia.org/wiki/Automobile_drag_coefficient#Typical_drag_coefficients
For a car with more room but a lower cd I'd look at a Gen3 or Gen4 TransAm, 1982-2002, but they are heavier, or a Toyota Camry or Corolla. Aero is more important than weight for long distance steady state driving.

 

AMAZING!

I have just spent about 30 minutes reading through the Ontario governments rules on the incentive for electric cars ($8,500 rebate) and I think that there may be a loophole. The rebate may be able to be achieved if I use a new glider as the base, and call it a demonstration car for the company "charliehorse55 electric cars" The rules state:

Applicants can apply for an incentive for the purchase or lease of automobiles that:

- meet all Canada Motor Vehicle Safety Standards;
- are registered in Ontario, where the registration in Ontario represents the first time the vehicle has been registered in any jurisdiction;
- are plated in Ontario;
- have a Gross Vehicle Weight Rating of less than 10,000 lbs (4,536 kg);
- are propelled by an electric motor which draws electricity from a battery of not less than 4 kWh in capacity;
- are capable of being recharged from an external source of electricity;
- are manufactured primarily for use on public streets, roads, and highways;
- have at least four functioning wheels; and
- are not low speed vehicles

And

Grants are not available for the following types of vehicles:
- vehicles that were converted to electric or plug-in electric from internal combustion engine ** If I am using a glider it never had an ICE installed!
- conventional hybrids that do not allow charging from an external source


Additionally:

Demonstrator vehicles including prototypes and other limited production run vehicles may be registered as an offical electric vehicle if **making them eligible for green plates and incentives**
- meet all program criteria (noted above)
- less than 500 km on the odometer at the time of purchase or lease.

 

I don't know about getting a new glider from an OEM but maybe a kit car body would also qualify?

 

What is a kit car body? Any good recommendations for one with low drag/4 seats?

Cost?

Thanks

 

Anyone here have experience with putting a lot of batteries into a small car?

Not a lot, but a moderate amount: http://www.evalbum.com/3060. I could have set the main battery box a little lower and kept the rear seat. I can also increase the width of the small rear box with 8 cells to fit 20 there, and might just squeeze 2 more in the main box for 50 total, 180Ah, so nominal 160V, 28.8kWh. But that would be it with a rear seat. The Tercel is larger so you might fit more under the hood than the 8 I could fit there with all the other stuff - charger, controller, DC/DC...

The Swift also has a Cd = 0.32, a stock curb weight of 1895 lb, 907 kg, and a bit smaller cross sectional area than a Tercel. I estimate that with the max 28.8 kWh I could fit, it would have about 100 mile range at 55 mph, 90 km/hr, and 80% DoD, about 2/3 of your goal. I don't think you can do it with a 37kWh pack. I would think you would need to use about 36 to 37kWh, so about 80% of a 45 to 46kWh pack. That is going to be very difficult to fit with the back seat in place.

I suggest you go to a junk yard with a tape measure and look for a Tercel, and any other donor you might consider, and estimate how many cells you could fit along with all the other stuff you need to put in. Get dimensions for controller, motor, charger, DC/DC, brake vacuum pump, and figure what space you need for relays, contactor, etc, then see what you can fit.

 

Canada hates kit cars....

http://www.tc.gc.ca/eng/roadsafety/tp-tp2436-rs200804-menu-685.htm

 

After a lot of research, I am making more progress on the design of the car. Components:

AFM-140 BLDC Motor - 95% efficient at my cruising speed
BRUSA High Voltage 200kW motor controller - 97% efficient
250 * 60ah Thundersky batteries - 475kg, +25kg for charger/BMS in batteries, 48 kWh - wired all in series. 950V peak voltage after charging, 750V during peak current draw.
Direct Belt Drive - 3.5:1 ratio of motor to drive shaft - this gives me a top speed of 165 km/hr and 0-60 in 5.5 seconds. Belt drive is usually somewhere between 98 and 99% efficient.

I have realized that since the electronics will be a serious investment, I should get a pretty nice donor car as well, so that it will last for a long time before the frame rusts away. I like the Toyota Camry XV40, as it has a low cd of 0.27, as well as a high curb weight of 1600kg.

Looking at a car like the Metric Mind's conversion of the Audi A6, I should be only adding the weight of the motor/controller, as the engine + transmission + exhaust + fuel tank + sound dampening weigh around 500kg. The Audi A6 has a slightly higher curb weight of 1750kg.

The main problems I need to solve are:

Belt tension
I don't want to destroy the motor's bearings by putting too much horizontal force on the motor shaft. I also need a way to adjust belt tension. I am thinking to make a motor mount that both secures the motor and provides support to the shaft. This mount will have a small amount of vertical freedom controlled by a strong bolt. By adjusting the bolt the distance between the motor shaft and differential will be changed.

950V DC/DC Converter and 120VAC inverter
I haven't looked into either of these categories too much, I hope that something is available. I may considering doing it in two stages - find an inverter to generate 120VAC, use that directly for the 120V plug. Then, use a modified PC power supply as my +13.8V source, powering it from the 120VAC as well.

950V Battery Charger
I have found a single one so far, a BRUSA charger. However they don't like to sell to enthusiasts (Metric Mind has them however) so some alternatives would be nice. I will continue to investigate my options.



Finally, to answer why I'm using such a high voltage, it's because I'm going to be using direct drive. With the AC motor I have chosen I need at least 600V pack voltage. Since the next step up for most components is 1200V, it makes sense to use a voltage as close to that limit as possible to minimize losses. On the flip side, I can wire my pack together with AWG 5!

 

Greetings

For your reference, here are my estimates.

1999 Miata
20kw battery
120 km @ 90 kmh

The power to maintain 90kmh is 16 kw. This all assume my calculations are correct.

Rob

 

1999 Miata
20kw battery
120 km @ 90 kmh

The power to maintain 90kmh is 16 kw. This all assume my calculations are correct.

120 km (72 miles) at 90 kmph (54 mph) requires about 1.33 hr. At 16kW that is about 21 kWh. My Swift only uses about 10-11kW at 55 mph, so I think the 16 kW may be a bit high, but don't know the relative weight and drag.

 

Overall:
I will use this car as a daily driver around Toronto, but I will also occasionally need to drive it around 180km to visit my parents and go skiing in Collingwood. I want a 250km range during ideal conditions

Cruising speed of 56 mph for 150 mile range

Ability to drive 120 miles in poor/cold weather - at only 50 mph if required

building for your 'max' range is going to add a LOT of expense for only occasional use. I would suggest you build to match your daily use, and rent/borrow a different vehicle for long trips.

I am assuming your 'daily' needs are probably in the typical 50 mile range, or less.... The added cost to bump that up to 150 miles just in batteries would pay for buying a cheap used diesel and converting to veggie oil.