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This needs to be engineered and is not a home project.
All EV conversions are engineering exercises, and they're almost all done by unqualified hobbyists. The size of the vehicle doesn't change any of the technical issues, but it does escalate the cost (which will be huge).This needs to be engineered and is not a home project.
Yes, big vehicles with big tires have a high first-gear reduction. A small car might only be 15:1, but the tires are half the diameter. A current Ford F-150 pickup has a 4.69:1 first gear, multiplied by torque converter ratio (because it's a torque converter automatic, but the bus is a manual so 1:1), multiplied by a 3.55 or 3.73 axle ratio, for 17:1 or so, but it still has little tires compared to the bus. As I said, it's the same design challenge as any other conventional vehicle (especially like a truck with live beam axle), with appropriate specifications used. The solution will be a huge battery, large controller, large motor, and substantial reduction gearbox (or skip the reduction and use a huge motor from TM4)... which will be no more difficult to design and build than a conversion of an MG Midget, but vastly heavier and more expensive.~40:1 total reduction in first gear.
Yes, and that is true of any conversion; being large or a bus doesn't change that. Requirements for commercial licensing and business profitability would be significant, just as they would be for someone wanting to convert their car and use it in a place with stringent licensing requirements or use it as a taxi. DIY converters make economically-driven decisions which compromise the safety and performance of their conversions every day.Engineering is much more than technical, Brian. It includes working within constraints to solve the problem and complete the project. Much of that is economics...
Thanks Brian and Remy for the feedback. Yes i’m just finished the engineering calculation, it’s seems crazy right for the capital expenditure for retrofitting this bus?Yes, and that is true of any conversion; being large or a bus doesn't change that. Requirements for commercial licensing and business profitability would be significant, just as they would be for someone wanting to convert their car and use it in a place with stringent licensing requirements or use it as a taxi. DIY converters make economically-driven decisions which compromise the safety and performance of their conversions every day.
Yeah man, the life cycle cost is very high for now, so i’m trying to adjust this.You will need recharging stations every 50km
unless you fill the bus with $200K USD worth of batteries that need replacing every few years
In Canada, that's probably true. In Indonesia you can get a taxi ride on a scooter.I seriously doubt any insurance company would cover a DIY conversion for use as a taxi.
So you agree: it's just like any car conversion used as a taxi - the size doesn't change the design process, but commercial service likely brings additional regulations. My guess is that in Indonesia if it looks like a bus on the outside and you pay the appropriate official, it doesn't matter what's under the skin... or maybe it's only school buses that are allowed to have passengers riding on the roof. More importantly, there is no reason for any aspect of the conversion to be unsafe, if the builder is willing to pay enough.Again - a DIY bus conversion is not "engineering" and, in most countries, practicing engineering where public safety design is being decided/approved without a license to do so will get you fines and a jail sentence. Even in Canuckistan.
A public bus has to be competently engineered in every sense of the word. SE Asia has enough highway carnage from buses without sprinkling in cowboy design mods.
That won't keep you out of fines and a prison sentence. Pretty standard to use your suggested reckless defense in the courts, Brian, which just pisses the judge off because you easily could have had a PE sign off on some safety design aspect (like sufficient braking down mountain grades).Maybe "I didn't realize that I wasn't allowed to do this" is the best attitude.
Some of the electric school buses here used liquid sodium batteries.Yeah man, the life cycle cost is very high for now, so i’m trying to adjust this.
What battery type should i uses? LFP or NMC battery? What’s the pro’s & con’s?
I agree, even some EVs from serious manufacturers (such as Volvo/Mack) use at least a two-speed transmission for this reason.I'd keep the transmission for both up and downhill purposes as it can give you greater speed in the flats and lets you use a smaller motor.
Or just don't fully charge the battery, leaving room for the energy of a full stop from highway speed for the amount of regenerative braking needed on a long descent. Yes, resistors are used to dissipate energy for braking in some cases, but that's typically in a vehicle with no battery (such as a traditional diesel-electric train, or those streetcars).Remember that you have ZERO "engine braking" down"hill" with a fully charged battery, so you might consider using some huge resistors (possibly boil water with them) to dump the energy into (Toronto's street cars did this in winter & heated the passenger compartment) brake fade (they call it "failure" when it's the driver going too fast downhill riding the friction brakes) downhill has killed a lot of bus passengers in SE Asia.
So I assume that you're doing that in your own conversion, since it will be used on public roads... right?That won't keep you out of fines and a prison sentence. Pretty standard to use your suggested reckless defense in the courts, Brian, which just pisses the judge off because you easily could have had a PE sign off on some safety design aspect (like sufficient braking down mountain grades).
Sure, and some cars ran on coal... over a century ago. Would anyone use a liquid sodium battery today? None of the current manufacturers of battery-electric buses do, as far as I know.Some of the electric school buses here used liquid sodium batteries.
There's a warmup time to use them - not sure SE Asians would have the patience 😂