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Discussion Starter #1
Hey all,

I was excited to find this forum as I have been thinking of doing a conversion for a very long time now, even drawing out plans to build electric vehicles when I was a kid but never being able to pull the trigger. I have in mind a small on-road/off-road vehicle (current choices are Suzuki Samurai/Jimny/Sidekick or something like a Daihatsu Hijet or Suzuki Carry) with switchable 2wd/4wd so I can maintain some efficiency when driving on roads. Unfortunately even with the Cybertruck coming I still don't think any vehicle on the market appears to satisfy exactly my requirements for an EV, so I want to build my own based on one of the aforementioned platforms. I am looking to be able to go 60-ish MPH and be able to travel somewhere around 100miles on a charge. I have my eye on Tesla model S batteries for the conversion, but I have very limited experience in power electronics and don't really know what is needed to do a conversion like this. I do however have background in electrical and computer engineering so I can learn pretty quickly. Looking for any help I can get!
 

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So, rough specs:

- Suzuki Sidekick-ish sized
- 2500-2800 lbs ish. Fairly light.
- 60mph top speed
- 100mile range.

You need probably a 32kWh pack, or something in that range.

Price that out, weigh that out, and then decide whether it's still a project you want to pursue.

Any ideas on motors you're looking at yet?
 

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Discussion Starter #3
I've got my eye on the Curtis 1238-7601 that they're selling on EVWest. https://www.evwest.com/catalog/product_info.php?cPath=8&products_id=210&osCsid=edf2hs8mr23hqeca7ojl2mt8b5

It's rated for 62 hp, which is close to that of the original samurai, but with more torque (102ft/lbs vs 76ft/lbs). I'm looking to build a pack from model S cells that has two banks of four cells in series for an 89.2V nominal system, which is within the operating range of this motor. If my calculations are correct that gives me a 41.4KWh pack, which is well within this range.

One of my big questions is how to find resources for building this pack. I have never built a BMS before and I would like to make sure this pack is built safely and can charge safely.
 

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I'm looking to build a pack from model S cells that has two banks of four cells in series for an 89.2V nominal system, which is within the operating range of this motor. If my calculations are correct that gives me a 41.4KWh pack, which is well within this range.
It looks like you're using the term "cell" where you mean "module" (an assembled group of cells with a housing and internal wiring connections). A Model S or X module is nominally 22.5 volts, or about 90 volts for four of them in series.

Two banks of four of these modules each would be eight modules, or half of the full pack of any of the 16-module Tesla model variants. If that's 41.5 kWh or so, then you would be using modules from one of the "85" variants, meaning 85 kWh for the full stock pack.

So yes, the voltage and capacity numbers are correct... but that's 440 pounds of modules, before you add a framework to hold them, housing to enclose them, wiring to connect them, and plumbing to cool them. Can you carry that much battery in this small vehicle?
 

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You didn't put any text in for the link, so it doesn't show in your post...
Curtis 1238-7601 at EV West

The "Curtis 1238-7601" part of that is the controller; in this package from EV West the motor is an HPEVS AC-34.

It's rated for 62 hp, which is close to that of the original samurai, but with more torque (102ft/lbs vs 76ft/lbs).
That's the peak power, which it can't maintain continuously, and the available power drops off with speed so at higher motor speeds it can only produce a fraction of that power... I doubt that this would be sufficient, unless you are keeping the transmission and shifting to put the motor at the speed where it can be effective enough. Most conversions using this motor do keep the original transmission.
 

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Discussion Starter #6 (Edited)
It looks like you're using the term "cell" where you mean "module" (an assembled group of cells with a housing and internal wiring connections). A Model S or X module is nominally 22.5 volts, or about 90 volts for four of them in series.

Two banks of four of these modules each would be eight modules, or half of the full pack of any of the 16-module Tesla model variants. If that's 41.5 kWh or so, then you would be using modules from one of the "85" variants, meaning 85 kWh for the full stock pack.

So yes, the voltage and capacity numbers are correct... but that's 440 pounds of modules, before you add a framework to hold them, housing to enclose them, wiring to connect them, and plumbing to cool them. Can you carry that much battery in this small vehicle?
Clearly I have a lot to learn about the terminology and also the mechanics of using the forum at all. I'll answer the questions from both of your posts as best I can.

Yes, I am planning to retain the original transmission in this vehicle and fabricate an adapter plate. I am confident that with the removal of the original engine and gas tank I will be able to hold the additional load of the batteries, especially in the suzuki carry example since it is a pickup truck rated for much more weight than that (800lbs payload, and the batteries will be mounted under the bed). I am also planning to modify the suspension on whatever vehicle I choose to compensate, provided the frame can handle the weight, which I also suspect that it can.

And yes, the parts would be sourced from one of the "85"variant model S vehicles.

EDIT: forgot to factor in the weight of the new motor which in the suzuki carry is about the same as the outgoing F6A. So there is definitely a concern here, but I think it is all dependent on how the weight is distributed.
 

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I am confident that with the removal of the original engine and gas tank I will be able to hold the additional load of the batteries, especially in the suzuki carry example since it is a pickup truck rated for much more weight than that (800lbs payload, and the batteries will be mounted under the bed).
Given that it looks like you don't want to carry much with it, a Carry might work out well, given the amount of space under the load floor for battery modules.

You would presumably want larger tires on a Carry, and a lot people do fit larger tires on these Kei trucks. It would be a good idea to keep a larger tire diameter in mind when considering gearing.

I am also planning to modify the suspension on whatever vehicle I choose to compensate, provided the frame can handle the weight, which I also suspect that it can.
...

EDIT: forgot to factor in the weight of the new motor which in the suzuki carry is about the same as the outgoing F6A. So there is definitely a concern here, but I think it is all dependent on how the weight is distributed.
Keep in mind that axle weight capacity isn't just limited by the springs - there are also the tires, wheels, bearings, axle housings and other suspension component, and braking capacity.

Yes, weight distribution is important, to stay within each axle's load rating, and for vehicle handling. This might work out well in a Carry, if you can locate the battery modules near the middle. There are a dozen generations of the Carry (and many generations of other similar vehicles from other manufacturers) and the engine position varies between generations, so you might want to look at what is available in terms of what space would be left for battery after replacing the engine (and fuel tank and exhaust system) with an electric motor.
 
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