Daihatsu Charade EV project, advise please.

Technical discussion on converting internal combustion to electric
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Miles
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Daihatsu Charade EV project, advise please.

Post by Miles » Mon, 03 Aug 2015, 02:53

Thought I would introduce myself as I am new here. I'm Miles, currently living in the Huon Valley Tasmania and have just bought myself an abandoned EV project.
It is a 1985 Daihatsu Charade. The EV conversion was completed a decade ago with lead acid batteries, but the vehicle has been left for a while and the 500kg of lead acid were knackered so they have been taken to the recyclers.

The car has an Advanced brand DC motor model 203-06-4001, which can operate between 72-96V DC. Controller is Curtis PMC Onroad 96-144V 500A and the charger is a nerdy home wired job, which I'm not even going to attempt to understand.

The motor has been setup with the clutch still operational between box and motor. I think someone had an alternator in place running off a belt from one of the driveshafts to charge the accessories battery.

I have decided to use LifePo4 batteries or something similar and am currently researching them. I know a bit about gel and lead acid batteries as I recently engineered my own off grid power supply, but this is a whole new ballgame for me. Lithium seems to be quite expensive so I am at a crossroad in the decision making process.

As the motor is rated 72-96V, I'm wondering how well it will propel the vehicle at 72V rather than the 96V it has been set-up for? At 72V it gives a continuous 12.1KW w/max 31.5KW and at 96V it gives a continuous 14.4KW w/max 51KW. I live in a very hilly part of the country so am a little worried lower power might be an issue. Charades aren't quite as light as the micros people so often convert, but I'm pretty sure this model was 655kg stock if my net research serves me correctly.
At 72V I'll be needing a new controller and I'm wondering if the money saved on batteries would get a new controller to run at the reduced 72V?
I guess I need to decide on all this before buying a charger.

I'm also thinking about a regen system due to the hilly terrain here, I think it would be quite useful. This is something I currently have no knowledge on.

Thanks in advance, Miles
Last edited by Miles on Wed, 05 Aug 2015, 13:01, edited 1 time in total.

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Daihatsu Charade EV project, advise please.

Post by Miles » Mon, 03 Aug 2015, 03:14

Sorry, I forgot to mention that it is my ultimate hope to get a travelling distance of at least 80km before recharging. This is how far the return journey is from my place to the Hobart CBD. It is a hilly drive and the hills are steep and long by Australian highway standards. There is hardly a level stretch of road and I'm thinking a regen system would really assist? I'd have to say that myself and many other people that drive this stretch of road often angel gear it down hills to save fuel. Not uncommon to be doing 80km/hr at the top of a hill and be climbing to 130km/hr at the bottom. (I would never go that fast obviously as it is illegal...) I'd really like some advice on what AH batteries I would need to cover this journey.

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Post by jonescg » Mon, 03 Aug 2015, 03:52

Your DC motor will mean no regen - not without a fair bit of additional features, and these can start to get complicated.

After reading your first post about a direct drive vehicle, I was going to suggest AC all the way, but it also depends on your budget.

If you want range, and lots of it, you will need something more energy dense than LiFePO4. It's pretty good for the price (90-100 Wh/kg) but if you need to go 80 km and it only gives you 70, then it kind of doesn't matter how cheap it was.

Consider Leaf cells if you want an OEM option, otherwise there's some pretty impressive cylindrical cells out there offering well over 220 Wh/kg. Pouch cells which use lithium cobalt chemistries are out there too, and these offer 180-190 Wh/kg although there are some pouches with well over 200 Wh/kg, just very low C-rate.

The Ah you want will be determined by the voltage you want to run. If you stick with the DC motor, you will be limited to about 160 V. Which means a 25 kWh pack using 160 Ah worth of cells.

If you go with AC, you can run up to 400 V, or as high as 720 V. This means the same capacity (25 kWh) would call for 80 to 40 Ah cells respectively.

AC is more expensive, but always worth it in my opinion.
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Post by Miles » Mon, 03 Aug 2015, 05:08

I'd rather stick with the DC motor that was installed. If I had to ditch that, I'd probably just start a project on another model I'd much prefer to convert.
This project is my first one and I'd like to get it up and running for minimal cost with as many of the already used components. It's really a project so I can learn more about EVs and how they work.

If it's going to be an overly expensive exercise to use batteries better than lifepo4 then I might have to adjust to not achieving my range and resort to recharging on the journey, which is an option, but an inconvenience.

Why is regen easier to engineer with AC rather than DC?
Last edited by Miles on Mon, 03 Aug 2015, 04:33, edited 1 time in total.

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Post by Miles » Mon, 03 Aug 2015, 05:11

Where can I buy leaf cells from? What Ah do they come in and what's the cost?

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Post by jonescg » Mon, 03 Aug 2015, 05:50

In that case, just get it on the road at the lowest cost possible; but still avoid lead.

See how big the useful battery volume is first. Then decide what will fit, and determine if the mass is excessive. If not, buy the appropriate LiFePO4 pack and enjoy your largely completed EV. If it is going to be too heavy, reduce the capacity until you have an acceptable mass, and go from there.

If you are new to the whole EV thing, then I suggest that you make sure the vehicle has a good coulomb counter like a Cycle Analyst, or equivalent. At the very least you need to have the amps being drawn while driving, and the pack voltage displayed clearly in front of you. Even these simple devices, combined with a clock and a reliable odometer will give you plenty to work with.

Regen can be done with DC motors, but only permanent magnet DC motors or (if I recall correctly) shunt-wound motors. If the armature is spinning due to an applied torque (like the road on the wheels, down a hill) power will only be generated if there is a strong enough magnetic field maintained in the stator, like from neodymium magnets. In the case of AC, the inverter (controller) is able to provide the necessary magnetic field to the stator.

AC is smooth, quiet, efficient, water resistant and maintenance free. But the inverters are disproportionately expensive compared to DC.
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Daihatsu Charade EV project, advise please.

Post by zeva » Mon, 03 Aug 2015, 08:04

Miles wrote: Sorry, I forgot to mention that it is my ultimate hope to get a travelling distance of at least 80km before recharging. This is how far the return journey is from my place to the Hobart CBD. It is a hilly drive and the hills are steep and long by Australian highway standards. There is hardly a level stretch of road and I'm thinking a regen system would really assist? I'd have to say that myself and many other people that drive this stretch of road often angel gear it down hills to save fuel. Not uncommon to be doing 80km/hr at the top of a hill and be climbing to 130km/hr at the bottom. (I would never go that fast obviously as it is illegal...) I'd really like some advice on what AH batteries I would need to cover this journey.

A vehicle like that is likely to average about 150wh/km around town, though hilly terrain could make it a lot worse. Your motor is Series DC type, which doesn't support regenerative braking. Angel gear in a petrol vehicle is pretty much the same as zero throttle in an EV (without regen), so you can just roll down a lot of hills. But regen is very useful on steep hills where you'd otherwise have to use brakes (and be wasting energy).

You might as well stick with a 96V battery so you don't have to replace the motor controller. 72V wouldn't really give any advantages - for a smaller size pack, better to just run smaller capacity cells at 96V.

So let's assume 200wh/km, allowing a third more energy for those hills. If you want 80km range, you'll need 80km x 200wh/km = 16Kwh battery pack. At 96V, that means 16000/96 = 166Ah batteries. So a close match might be 32x 160Ah Winston LiFePO4 cells.

Bear in mind that 200wh/km was a bit of an estimate. It's hard to predict exactly how much energy a given vehicle will use per km. As Chris said, it'd be a pity to build the thing and not have it meet your requirements! (Though you could always add a few extra cells for more range later if necessary.)
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Post by Miles » Wed, 05 Aug 2015, 20:53

Thanks very much to everyone for the helpful advise so far. All this info is really helping me learn a lot more about EVs and the calculations are coming in very handy. I can see things becoming quite expensive if i stick to wanting a range of 80km in hilly terrain without the option of regen. I'm considering perhaps scaling back on the size of a battery pack and perhaps just using the car for all the trips and tasks in my local town which is only 6km away.
So If I need a 160Ah pack at 96V to cover 80km, how far am I going to get with say a 100Ah pack or a 60Ah pack? Is it a simple percentage or the original calculation? ie 100Ah=50km, 60Ah=30km
Last edited by Miles on Wed, 05 Aug 2015, 10:56, edited 1 time in total.

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Post by evric » Wed, 05 Aug 2015, 21:26

If you have hills, the 60Ah pack would get stressed by the large motor current when going up hills - especially at a low voltage of 96V. If you want your pack to last a while... I would suggest 160Ah.
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Post by Miles » Wed, 05 Aug 2015, 22:25

evric wrote: If you have hills, the 60Ah pack would get stressed by the large motor current when going up hills - especially at a low voltage of 96V. If you want your pack to last a while... I would suggest 160Ah.


So 100Ah isn't going to cut it either?

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Post by 4Springs » Thu, 06 Aug 2015, 00:40

I converted my vehicle originally using lead-acid batteries. I then upgraded to lithium after that. One benefit of doing this was that I could calculate exactly how much power I used to travel a certain distance. So when I was designing my lithium pack I had a good idea how big it needed to be. When I paid for my expensive battery pack I only spent exactly how many dollars I needed.
So do you have any information on how much power the car originally used? What we are after is something along the lines of:
"After travelling 40km it took 8 units of electricity (8kWh) to charge up".
In this example 8000/40 = 200 Wh/km (amazingly the same as Ian's estimate!).
If you have that information you will be able to make much more accurate predictions about your lithium pack.

As an example:
Brumby as lead-acid was 250-300 Wh/km depending on terrain.
I wanted a lithium pack that would let me travel 60km comfortably. So 60*300=18,000Wh = 18kWh.
My lead-acid pack was nominally 144V. I knew my controller would handle up to 170V. I looked at the available lithium cells and settled on this combination:
48 cells, nominally 3.2V per cell = 154V nominal. This will be closer to 170V when charged fully.
I chose the 130Ah cells. So 154*130=20,000 = 20kWh. My pack is nominally a 20kWh pack. It cost me roughly $8,000 at the time (and a lot of time and effort because I made the BMS myself).

The lead-acid pack was about 500kg. The lithium one is about 250kg. So the calculation above to ensure I could get 60km of range was conservative.

When I tested the completed vehicle I found that I had reduced my consumption to about 220-270 Wh/km. So in theory my 20kWh pack will get me 20,000/220=91km.
In practice the one range test trip that I took was 108km reasonably slowly on flat roads. This took 24kW to recharge, so my pack is more like 24kW than the theoretical 20kW.

Ian's estimate of your consumption was 200 Wh/km, which you'll notice is less than mine uses. This sounds right, the Charade will be better than my vehicle which is relatively heavy and aerodynamically poor. But this is on the flat - it would be quite different going up those hills.

Are you going to the Launch in Hobart on the 15th? It would be great to have a chat!

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Post by Richo » Thu, 06 Aug 2015, 20:49

Miles wrote:I can see things becoming quite expensive if i stick to wanting a range of 80km in hilly terrain without the option of regen.

Yep your looking at the initial cost which most people balk at.
In the long run (battery life) lithiums work out cheaper than lead acid.
Miles wrote:I'm considering perhaps scaling back on the size of a battery pack and perhaps just using the car for all the trips and tasks in my local town which is only 6km away.
And that is the most common solution - change range requirements.
Which is much easier than getting more money Image
Miles wrote: So If I need a 160Ah pack at 96V to cover 80km, how far am I going to get with say a 100Ah pack or a 60Ah pack? Is it a simple percentage or the original calculation? ie 100Ah=50km, 60Ah=30km

Pretty much as it's only an approximation.
The concern will be to watch the "C" rating.
As you decrease your pack size the demand on the batteries will increase to produce the peak motor power.
So at some point rather than getting cheap prismatic lithium cells you may need to change to more expensive "performance" cells.

For example lets say you need 50kW for the motor.
A 16kWh pack needs to have a ~3C rating.
Change your range to 6km or ~2kWh and you now need 25C.

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Post by Richo » Thu, 06 Aug 2015, 21:07

Miles wrote:I can see things becoming quite expensive if i stick to wanting a range of 80km in hilly terrain without the option of regen.


Don't over emphasize the importance of regen.

Lets consider regen at an improvement of 10%.
A 16kWh pack costs ~$8640
So the value of regen at 10% would be $864.

Now to get regen you need to change your motor, controller, adapter plate and coupler.
I doubt this could be done for less than $3500.
For the same $3500 in batteries and using your same DC setup you would get an increased range of ~40%.

If it was a NEW build and you had purchased nothing then a regen system might be an option.
But it still would only give some 10% improvement over a comparable DC system.
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Post by chocman » Fri, 14 Aug 2015, 02:45

I got a land rover perentie that is manual. Can I place a dc brushless motor on the inner wheels? To augment/supplement the acceleration

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