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Forum Index : EV's : My latest EV project
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| galderdi Regular Member  Joined: 12/08/2016 Location: AustraliaPosts: 99 |
Hi all, I have previously had two unregistered EVs for grass roots motorsport. But now Motor Sport Australia is having a hissy fit about EVs so I can't use one there. So I decided to start again and this time make a road registered EV. It is to be themed off the Porsche 550 Spyder made famous as the car James Dean died in. Here is the target:  This is where mine is up to:   Obviously I am forced to make some changes partly to satisfy the legal requirements and partly to make it achievable. I started in March 2021 so I am fairly pleased with my progress so far. I am targeting March 2023 to have it on the road. |
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| Davo99 Guru  Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
That surprises me. I would have thought they would have been all over EV's with the current mentality of the world. What is their objection to them? What sort of batteries and capacity and Motor output are you looking at? Will this not be expensive to have certified and are you limited in conditions on rego or anything? Be interesting to follow your Project. |
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| galderdi Regular Member Joined: 12/08/2016 Location: AustraliaPosts: 99 |
Thanks The objections from Motorsport Australia are vague and unstructured. They tried to claim that I needed to go through some fictitious extra EV process to have them allocate a class. But that is BS because the event was a regularity where there are no classes. So they were just running scared. They just latched on to any excuse to kick me out. They wouldn't even give a refund for my entry. I had been competing in EVs under them for more than 4 years before they even realised. There was no written rules. I interpret all this as just being scared and ignorant. They wouldn't even talk about it. I still hear of other EVs occasionally competing but they are only getting away with it because Motor Sport Australia don't hear about it......RANT OVER....for now I am in two minds regarding power. I have already re-purposed my 8 inch DC motor for this project. My first option (fall back position) is to re-use my existing controller with a new battery. It would run at 172v and 1000amps. It realistically provides about 90-100KW. This would give me exactly the same performance as my previous car. That performance was great up to 80kph but mediocre after that. So my latest thinking is to upgrade the batteries and controller to achieve slightly higher voltage to improve the performance between 80 and 120. I'm not sure what voltage the motor will handle so that would require some testing before I could quote any specifics. The car is only 550KG assuming I stick to the original option so it will be awesome to drive. I originally hoped to make it AWD and based off a Locost chassis design. But my engineer talked me out of that direction because of the engineering costs. He recommended the current chassis because it is a known quantity. He has already certified many of these before. So long as I don't alter the chassis it should just need some inspections. That direction reduced the engineering costs by many thousands. It will be fully registered with no restrictions. Oh and I forgot to add the link to my full set of progress pics: https://flic.kr/ps/3W7voH Edited 2021-09-17 14:57 by galderdi |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 458 |
Looks very impressive. Building a home made vehicle and getting it registered in Oz is also a very big move. 90 to 100 kw seems plenty for such a small car. Are you using a gearbox? Is the lack of power above due to the motor running out of revs or does the torque curve fall off at that speed? Wow dragging 1000 amps form a battery bank is a lot of current. I am guessing that your range would fall off fast if you tried to run flat out and pull that much current. What range are you aiming for with this car? I have not long ago added a capacitor bank to my stand alone solar. I did it to help with starting currents as we have a 24 volt 660 amp hour battery bank but the inverter struggled with starting an air compressor. With the capacitor bank it fires it up easily. I added a 500 farad 24 volt bank which is capable of supplying 1900 amps. Just wondering if you are using capacitors in parallel with your batteries to assist in high acceleration or regen situations? Anyway nice photos, very nice work, good luck with registration Pete |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I was watching some EV Vids recently. The owners must get driven Nuts with people asking why don't they put a solar panel(s) on them to charge them up? There were HUNDREDS of comments like this over a half dozen vids or so I watched. People have No idea about solar, electricity, batteries or anything else electrical. Seem to think you throw a Solar panel on something and that's all you need for endless energy and you can power a vehicle or charge a battery like the thing will pump out 100Kw. What was most laughable was how many indignant commentors took the position of the EV builder being stupid because they had overlooked that obvious suggestion that the superior intelligence commentor had seen as obvious. Ugggh! Godoh, I was looking at Traction/ Forklift batteries last week on Fleabay. The prices have dropped a LOT. I take it due to lockups and shutdowns they are trying to move some of the things. There were 48V, 600Ah packs going for $1200. Easy to re configure and give you an extra double the capacity you have now for a very good price. Don't know if you need or would like more capacity but if you were thinking of it, seems now might be the time to look into it for a potential Bargain. |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 458 |
Thanks Davo, we are OK with the battery bank we have now, ours are VRLA batteries, pretty expensive but we only have a very small house, and an oversize solar system to allow for all the foggy mountain weather we get. Sounds like the sellers are trying to get rid of floor stock, that price seems very low. Thanks Pete |
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| galderdi Regular Member Joined: 12/08/2016 Location: AustraliaPosts: 99 |
Godoh: The 90 to 100KW is no problem. Both power and torque taper off quickly as revs rise. Just the opposite of what you experience in a combustion vehicle. Yes there is a gearbox. In 1st gear you have the gearing advantage but run out of revs at about 50kph. In 5th you loose the gearing advantage and still run out of revs at about 110kph. The problem is back EMF which resists high revs. The way around it is higher voltage. I did the math on super capacitors. To make a noticeable difference you would need enough capacity in the capacitors to cover the upper portion of the power curve for a typical period of acceleration. This would mean about 4 sets of capacitors. That is too much space and weight for my purposes. With Super capacitors amps are no issue but capacity is an issue. 1000amps is from the controller to the motor not from the batteries. The Controllers always take the power from the batteries in the form of maximum voltage (172v in my case). At low RPM and full acceleration they lower the voltage and increase the amps (within the power limits of the system). So at initial acceleration the output is around 1000amps and 90volts (90Kw) and the input would be 523amps at 172v (still 90kw). The 1000amps output 523amps input literally only lasts a portion of a second before it begins lowering dramatically. As the revs increase the controller decreases the output current and increases the voltage until the maximum voltage is reached. At that point the system reaches the limit of speed. Increasing the input voltage allows the system to achieve higher revs equalling higher speed. But it comes at the expense of added battery weight. Davo: Thanks for the tip. I haven't looked at those yet. But I will. I doubt they will suit my requirements though. I have very small physical space and low weight requirements because it is such a small car. So I can't afford inefficient batteries. I have some in mind that would fit in the space (I think) and would weigh about 100KG. They will give me about 14Kwh which I think will give me about 150km of range if driven responsibly. Am I missing something though 48v at 600ah is 24kwh. That would be massive and $1200 is very cheap. |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 458 |
Hi Galderdi, I have 660 amp hour cells in my solar system. They are VRLA but weight about 35 kilos each. I am assuming that the traction cells would weigh similar so the overall weight would end up around 840 kilos. I would think that is way too heavy for a car. The ones I saw on ebay were second hand, hence the price. I paid around $3500 for a 12 volt bank of BAE cells, of course they were new. Sounds like the motors you are using are acting the same as a Series wound DC motor. If it were possible to have a Compound motor then the torque curve could be flattened. Anyway sounds like you are on top of it all and from what I have seen are doing a great job. I have dreams of building an electric car one day. Deciding on what car to do it to is the problem. I live in a place where all wheel drive or 4wd is pretty important in winter, and a good long lasting body of the car would also be needed. Oh well dreams Cheers Pete |
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| galderdi Regular Member Joined: 12/08/2016 Location: AustraliaPosts: 99 |
Thanks Pete My previous two EVs didn't need much range and I used a 7Kwh portion of a Chevy Volt pack. That cost $2,500 but that was quite a few years back. That pack is about 65Kg from memory. I need at least 10kwh to make the car even remotely usable. I need to keep the battery weight to about 100kg otherwise I risk exceeding the weight for the vehicle and the engineer may insist on more tests/cost. Yes this is a series wound motor. I considered changing to an AC motor. But there is a big gap in the market between those running on around 170v up to 350v and up. 170v would not give me any real advantage and I can't fit batteries to support 350v. I figure I will stick with my current setup and I can always upgrade at a later date when different options become available. A Subaru Brumby might be a good option for you. AWD and a ute giving options for battery installation. Plus it's old enough to not face the component integration issues most modern (2000 or later) vehicles face. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I wasn't thinking of your requirements so much for your Vehicle as Godoh's for his Home. You certainly wouldn't want to be carting round 1100Kg of batteries in a sports car! I presumed you would understandably need something more light weight and power dense like a Lipo derivative. LA is still a very viable Tech for many things, I don't think mobile application's is one of them however! :0) Yes, it is cheap for the reserve you get and makes the Commercial lithium battery derivatives look like a joke IHMO. There seems to be a LOT of deliberate Misinformation about Traction Batteries parroted by the lipo obsessed, which I believe is the apt term for the way many go on. We have discussed the Fork batteries here for home use and the reality is they are VERY cost effective with few drawbacks for STATIONARY/ off grid application. When one considers a power wall is 12Kwh useable and costs $15K and a $1200 (plus ancillaries) 24Kwh pack gives 19Kwh useable, it puts things into perspective. Double your spend on another Forklift pack and you have 38Kwh Reserve and you would rarely have to dip below 50% DOD if that ( They are rated to 80% DOD which is often maligned) and they are going to have a Very long life and give a lot of reserve. If one threw a generous size solar array at the things which would also be cheap as chips now, I'd say people in the typical weather conditions of Oz, (Barring maybe tassie or mountain areas) would rarely have to rely on a generator. To this end, I'm currently playing with an idea for running inverters mainly off solar. It's hard ( and expensive) to find controllers that will supply the kind of amps an inverter will pull. My idea is to have a Smallish/ low cost Controller and by pass it with heavy loads. I bought some Battery charger boards off Fleabay. They simply switch on and off at a set voltage parameter. Using a large array and small batteries with a decent Inverter, The voltage monitor bypasses the controller when the voltage drops, say when the inverter is running. When the batt voltage comes up after being fed whatever amps the panels can produce ( possibly hundreds) the voltage monitor drops the 500A relay and the charging is all handled at a much lower rate but the controller. I don't see a need to run through a controller when there is big amps being pulled that can come straight from the panels. There are panels that are suitable for both 24 and 48V setups so it's relatively straight forward. The Chyneese Hybrid Inverter/ Chargers I have been looking at will charge at a rate less than they will supply so create a negative drain on the batteries even if there is sufficient solar input available to power the load. This way would by pass that road block and keep the batteries seeing as little discharge as possible. Would be interested to hear what sort of batteries you are intending to use and the reasons behind them. Seem to be different ones coming out much more regularly these days. |
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| galderdi Regular Member Joined: 12/08/2016 Location: AustraliaPosts: 99 |
Cool, thanks for clarifying. I haven't narrowed my options just yet. I am still tentatively aiming for Mar 2023 on the road so I don't want to purchase the batteries too soon and have them sitting on the shelf all that time. One option I am considering are 45 x LiFePo4 3.2V 100Ah. Giving about 14kwh. Based on early measurements they will fit. I do need to redo those measurements as I now have the motor and gearbox in place. They will be about the 100kg I require. The plus side is LiFePo4 are resistant to fire. They to do burn, but not in the same explosive way as many other chemistries. But the down side is they are only rated for 300amp bursts. I can probably go a shade higher because it would only be a second but I will still be struggling to support the 1000amps I spoke about earlier. Having said that I have driven my previous EV set to 500amps output and it was ok but not all that inspiring. By my calculations I would expect 300amps input to support about 573amps output and limit the power to about 51Kw. Not ideal. So I am hoping I can find a better option in the next 12 months. I think if I can find a combination that would support 400amps in I could squeeze about 750amps out. That would be a good compromise. |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
Hi Greg, Nice work, been watching your previous build for some time.  I did see a documentary a few weeks back about electric cars, mostly interested in the drive-train they have mostly moved to high voltage very high speed motors (small in size) and then gear it down a lot, seems to be working well, sort of reminds me of these cordless drills (angle grinders) that are geared down and provide a lot of torque. Years ago messing around with old car generators using them to power model electric trains, the 12v volt generators used to run quite well on 24v, they would always rev to a certain speed and go no further, at the time this suited the purpose. Later on as an experiment we lowered the field voltage using a resistance bank, the result was less power to start up, but the motor would rev out a LOT higher and was not held back anymore, next idea was to switch the resistance onto the fields after the initial speed was reached, this worked but found it too fast and unsafe for the train track. Not sure if this helps or not, just an idea. Your Aluminium work is looking good. Cheers Aaron Off The Grid |
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| galderdi Regular Member Joined: 12/08/2016 Location: AustraliaPosts: 99 |
Thanks mate. all information is good information. Circling back to the battery question. Another leading option are Nissan Leaf cells. They are rated to 540amps peak. Pretty much the same rating as the cells I am currently using. But my cells are too small and too old. So leaf cells are a good candidate. |
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| galderdi Regular Member Joined: 12/08/2016 Location: AustraliaPosts: 99 |
Another cell that I am tending back towards is the Headway. These are still a LiFePo4 cell and are rather small at 10ah each. But they handle great current output at 100amps each. So if I string 8 sets in parallel I'll easily handle my current requirements and will give me 11.5 kwh of capacity. They also have the added advantage of more flexible packaging. I can design the housing to make use of every tiny corner of the allocated battery area in the car. 8 sets would weight 125KG so still around my target weight. |
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Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1057 |
We did this when I was at Uni back in the 90's. Played with a big DC motor. We would lower the field current to make it go faster & raise the field current to slow it down. Had to record & plot everything. The reason being (if I remember correctly) is that with a lower field current, a lower back EMF is generated & the armature current rises, speeding up the machine, if possible to regain the equilibrium & vice versa. Brian ChopperP |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
It would have been the mid to late 90's when we (my father and I) experimented with this. Just had a look at a small forklift motor 24v 2800rpm series wound, its a bit of a power waster unloaded, but might make a solar powered something out of it. Those Headway cells are pricey, (Hi drain cells seem to have a short life) they may be had cheaper from Alibaba or Made In China outlet, the manufacturer may be listed there, quite often thats where these local suppliers get them from, A few catches though, usually sold in bulk and shipping would have to be arranged yourself or by some middle man or broker arrangement or whatever they call it, don't forget customs charges as well, could be cheaper than the horrific shipping charges seen on Aliexpress. Would not be surprised if that all changes. Cheers Aaron Off The Grid |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
So much on there I would buy for reasonable Freight Costs. I don't know what their Shipping scam is. I'f wait a month like everything else to get it if the shipping costs were justifiable. Don't know if they are idiots or just think people in the west are. I was looking at some engines earlier in the year which had Freight at about 3x the cost of the engine. Contacted 4 Different companies selling them and got insulting offers from all. One company seemed to think that doing $32 off a a $1600 shipping quote on a $400 engine should make me as thankful as if they gave me a teenagers Kidney's or something. US fleabay is the same. Moronic shipping charges. Couple of years ago I got something sent from Canada. Forget the exactly Figures now but it was something like $10 more for the product and $70 less in shipping than from the US site. When it arrived I saw it had been sent direct from the US anyway. |
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| galderdi Regular Member Joined: 12/08/2016 Location: AustraliaPosts: 99 |
  Yes Headway cells are a little pricey going by price per Kwh. But They suit my requirements. I explored the idea of ordering from China. It is a problem when talking about lithium as freight companies are super cautious. I'd rather deal with someone local. I won't name names but my previous battery supplier let me down so I won't be going back to them. I made a bit more progress over the weekend. The left door frame is coming together. I need to make a new sill panel first so I have a good point of reference for the lower edge. Then I can add the skin. I also completed the motor mounts. Edited 2021-09-27 13:39 by galderdi |
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| galderdi Regular Member Joined: 12/08/2016 Location: AustraliaPosts: 99 |
Here is the latest on my door. It isn't attached just yet but you get the idea.   |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
You made/ modified that yourself? DAMN impressive! You clearly haven't done your trade as a panel beater in the last 10 Years. All they know how to do is unbolt something and replace it now. When they ring wreckers, not only want the suitable Panels, they want them in the right colour with a perfect paint job. None of the Johhny come latelys would have the skill or patience for real and quality work like this. Hard enough finding a Painter that can actually paint. Brilliant Job! |
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