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Old 05-14-2018, 09:29 AM   #1
Mini-Skoolie
 
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Bus EV Conversion?

Hey!


Again, I've found myself inspired to commit to living in a camper conversion. Right now, it's not feasible, but I have a new idea that's got my gears turning so I want to do some discussion about it!


Earlier this year, I was on here asking about city/transit buses and I tried figuring out if it was sensible to get my hands on a hybrid. I don't think it is possible, or at the very least it's not practical or worthwhile... As cool as it would be to have the Prius-style "use my motor as a generator when my battery is low" built in, I've moved on from that idea.


When having a discussion with a friend, they pointed out that vehicles can actually pretty reasonably be converted into EVs. And if you're starting with a vehicle that already has a messed up engine/transmission, it can sometimes even be cheaper or similar in cost to having repairs on the old systems. That definitely depends on a lot of factors, of course.


Anyways, I originally wouldn't even touch a dead bus with a ten-foot pole, but reading more and more about EV conversions, I'm actually getting pretty interested in trying to buy an out-of-commission aluminum city bus for next-to-nothing and converting it to an EV. I've been looking into recycling old batteries from things like laptops and cell phones, and that is seeming like it could at least be useful for storing solar power for a camper's electrical.


Of course, a lot of what I'm reading about is geared towards smaller vehicles and often with smaller ranges. There's one guy who's got a lot of youtube videos about converting an old Volkswagen Van into an EV, and he seems to do a good job of explaining things and showing his work. If he can scale up a normal EV conversion... why can't I scale it up more?! Let's talk about that!


So, I think a medium-size city bus would be large enough for me. I think they're in the ~34-44 passenger range? I'm currently traveling and using a lot of public transportation, and definitely feel like the smaller buses here seem spacious enough. Especially if I could pull off a roof raise. And, for whatever it's worth, I've gained a lot of trust in city buses considering these things can survive Vietnam city traffic. Haha


Assuming we're working with a bus of that size, do you think an EV conversion is sensible with the weight of a camper conversion on the inside? Do you think we need to double-up on motors? Do we need to have a motor for each wheel? I'm still trying to wrap my head around ranges and battery bank sizes/capacities and how they interact with controllers, but functionally the range is not too important to me as long as it's about 1.5x the average distance between charging stations in the US. (Which, I'm hoping will decrease over the next 1-3 years.)



What do you think?
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Old 05-14-2018, 11:03 PM   #2
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What's your budget?

Where will you source wheel motors and battery packs?

I'd think that an EV bus is technically possible but not very practical, particularly one not on a predetermined route with available charging stations.

I wouldn't even consider EV for an RV that would be traveling the country.
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Old 05-15-2018, 04:01 AM   #3
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My budget is pretty open-ended, but keeping costs lower is definitely preferred. This is as much a thought experiment as it is a plan at this stage.


There are lots of options to source the motors and batteries. It seems like lithium ion batteries can be scrapped from junk laptops pretty easily, and if you're lucky a lot of them can be had for fairly cheap. I recall seeing the occasional laptop at Goodwill for ~$30-50, and a lot of thrifting can be done on social media if you're patient and willing to go pick stuff up from people. Here's the guy who did that VW bus EV, is him making the second battery bank out of 18650 laptop battery cells. It could make the planning phase a little more complicated and delicate, but there's also cell phone batteries and a few other pieces of tech that have pretty standard battery form factors. Mixing and matching batteries is one of those things that should be "technically possible."


Assuming I had solar panels and maybe some kind of generator (maybe one that uses the same fuel as, say, my stove or water heater), going away from charging stations doesn't seem all that intimidating. Maybe I have to be patient, but I am a pretty patient person.


Speaking of solar power and/or a generator, do you think I should share the battery system between the motor and the camper? Is there a controller that could kind of intelligently borrow from one battery system if the other is starting to lack?
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Old 05-15-2018, 06:32 AM   #4
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Some possible ideas. Do you know how many cells the Tesla uses? In the average labtop there are 9.. If you do the follow the sun trip routes your daily mileage is under 50 miles. Better to start with a broken EV bus. Several were on auction lately. I doubt that there is any specific experience about your experiment. So you would be a trailblazer. Our daily driver is an electric converted geo metro. That is a very lightweight car and it has about 100 miles range. Good luck. Later j
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Old 05-15-2018, 11:26 AM   #5
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Thanks for your input, Joe!


I did some quick tablecloth math and tried to be *really* conservative.


~200V target voltage for motor/controller. (~144, ~188, and ~200+ are all possibilities based on what parts I can get my hands on.)
3.7V, the voltage of a 18650 laptop battery that's in good health.
The assumption that I can salvage 5 healthy batteries from a scrap laptop. I'm of the understanding that most laptops have more like 6 batteries, but I could be seeing mostly tutorials that use smaller batteries or whatever.



200/3.7 = ~54 batteries to get up to 200V with one battery series. Assuming 55 for a clean number. Our assumption is that we need to scrap 11 laptops to get one battery with a target voltage of 200V. IIRC one laptop battery cell in good health is ~1,000 amp hours.


Do you have any info (manufacturer, model name, year, etc.) on these "broken EV buses" you mentioned? That definitely has the potential to be a better starting point, but it also has the potential to be very specifically engineered to work with certain parts. Worth looking into, for sure!
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Old 05-15-2018, 12:17 PM   #6
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The only problem I see with making your own parallel battery brick is that the 18650s need to all be within 5%-10% capacity of each other. If not, then the weaker cells will pull down the stronger cells. That will limit both initial capacity, longevity, and safety.

Also, keeping the batteries cool will be a priority as you really don't want to have a pocket-bomb x1000 (i.e. thermal runaway).

Oh, and armor them - I think we're seeing a Tesla burning up almost weekly right now. When those batteries catch, look out!

Although I applaud those who make their own battery packs like this (and am amazed at what can be done with them), I'm also horrified by the dangers these packs pose. This is one thing that should only be done with "great care". Build them nice 'n neat with similar aged batteries - and don't forget to check each cell's capacity before packaging them together. Keep those capacities as close together as possible....
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Old 05-15-2018, 12:32 PM   #7
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Thanks for the words of warning.

I definitely plan to test the batteries. The rough plan is to sort them by rough voltage/capacity. The number of batteries I can get my hands on will determine how selective I get to be, but I will at least be aware of what I'm working with if it's less than ideal. If I'm able to get my hands on a large volume, I'll probably try to resell the bottom of the bunch (listing and pricing them as less-than-stellar, I'm not about sharking people) to either recoup cost or help me get more better batteries.

Regardless, I plan on being pretty conservative and trying to use a charge controller/monitor that won't let me go above or below the top/bottom 10% usable capacity. I'd much rather have '75% of my potential' than risk burning my system up. Y'know?

What do you think of jehugarcia's format (from the video I linked above) for his batteries? It looks pretty clean, and I was planning to draw some inspiration from his setup.

The motor/controller is going to need a cooling solution, so if I'm storing the batteries in the same area as the motor(s), I'm going to try to "cool" two birds with one stone.

Also, what specifically do you mean by "armor them up?" It sounds like a good idea, but I am not sure I'm following what you're suggesting.
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Old 05-15-2018, 06:05 PM   #8
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Quote:
Originally Posted by scapegoatwax View Post
Thanks for the words of warning.

No problem. I've worked on high-voltage / high-amperage projects before and learned alot about the care and safety needed around such "animals" (certainly not everything, though!).


Quote:
Originally Posted by scapegoatwax View Post
I definitely plan to test the batteries. The rough plan is to sort them by rough voltage/capacity. The number of batteries I can get my hands on will determine how selective I get to be, but I will at least be aware of what I'm working with if it's less than ideal. If I'm able to get my hands on a large volume, I'll probably try to resell the bottom of the bunch (listing and pricing them as less-than-stellar, I'm not about sharking people) to either recoup cost or help me get more better batteries.

If you are recycling old laptop batteries, then you will - by definition - be working with "less than stellar" cells. There are youtube videos on testing the cells and finding their capacities. Not hard, just not a whole lot of fun either.


Quote:
Originally Posted by scapegoatwax View Post
Regardless, I plan on being pretty conservative and trying to use a charge controller/monitor that won't let me go above or below the top/bottom 10% usable capacity. I'd much rather have '75% of my potential' than risk burning my system up. Y'know?

I'd be a little more conservative than that. I'd leave the bottom 20%-25% and maybe the top 5%-10% depending upon what the weakest cells in your pack are at (to give them room to age). Remember that those weakest cells will pull the whole pack down, and after a certain point those cells will not readily take a charge any longer. Again, if you are recycling old laptop batteries, they have probably already gone through 60%-70% of their cycle lifetimes and are on the downhill slide.


Quote:
Originally Posted by scapegoatwax View Post
What do you think of jehugarcia's format (from the video I linked above) for his batteries? It looks pretty clean, and I was planning to draw some inspiration from his setup.

Sorry, I didn't watch his video. I've seen a few like that (and I'm assuming what I'll see... ya, "'assuming' makes a ... outta u and m")....


Quote:
Originally Posted by scapegoatwax View Post
The motor/controller is going to need a cooling solution, so if I'm storing the batteries in the same area as the motor(s), I'm going to try to "cool" two birds with one stone.

Well, it really doesn't need to be more elaborate than a good fan and steady temps / humidity....


Quote:
Originally Posted by scapegoatwax View Post
Also, what specifically do you mean by "armor them up?" It sounds like a good idea, but I am not sure I'm following what you're suggesting.

Encase the pack in some steel, carbon-fiber, etc. Try to keep them from getting punctured in an accident. Lead-acid getting punctured isn't too big of a deal. Li-Ion getting punctured is a recipe for disaster. We're seeing Teslas burning to the ground and killing their occupants in short order from collisions causing punctures in the Li-Ion battery pack. Once one cell goes they all will go, just like one match in a book setting all of them off....
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Old 05-17-2018, 12:11 AM   #9
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Oh yeah, I recognize that I'm generally going to be dealing with batteries that are far from brand new, but I don't think it's unreasonable to expect that at least one battery per laptop would still be in fairly good health.


Like I said, I plan on testing all of the batteries and sorting them according to their condition. So, I'll have a bin for "great" cells that are close to spec in their voltage and capacity, a bin for "good" cells that are a little off in terms of voltage or capacity, a bin for "okay" cells that are more than a little off in terms of voltage and capacity, and then a bin for "bad" cells that are not worth using in a battery pack in this application.


Then, depending on the volume of batteries I have versus the volume of batteries I need, and how my funds are looking, I might try to resell the "bad" or even "okay" cells to put towards buying more batteries in hopes of getting more "good" or "great" ones. Again, I would be listing these as weaker batteries (either as a lot with a range of specs, or individually with specs), I don't want to be dishonest or try to fool anyone I'm selling stuff to.


Yeah, I was just giving an example of not going above or below the top and bottom 10% of the capacity. When time came to actually build and tune things, I'd be using a much more informed and specific target top and bottom capacity. We also need to account for the differences in 'where' the top and bottom of each cell is, which means there's ultimately more padding needed in the unusable range. At this stage, I'm trying to be made aware of these finer points. When it comes to more a more formal planning stage, I'll take each fine point into a lot more specific consideration.


Right now, I'm still trying to string all the concepts together and figure out the general plan of attack.


Do you have any idea what kind of motor/controller assembly might be right to consider for a project at this size/scale?
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Old 05-17-2018, 11:01 PM   #10
Mini-Skoolie
 
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Hey folks, did I make up aluminum-frame buses? I started looking around to see if I could find aluminum-frame transit buses to see where things were at.


I saw a few different models of transites bus for sale, but none of them appeared to have aluminum frames. The New Flyer(IIRC?) 40LFs I saw said they were made of lighter carbon steel that saves like ~1,000lbs compared to some alternative, but I don't know if that is on newer models (I saw this point on their website, talking about new buses) than the ~2003 I was looking at.


Should I be looking for somewhere special to find an aluminum-frame bus? If they exist at all. Haha
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