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Discussion Starter · #1 ·
I started this project many years ago... acquiring parts as they came up. In the meantime, electric vehicles have become much more popular and pervasive. Therefore, more parts in the junkyard for cheap.

For my project, I have everything but the batteries. Controller, motor, etc. I am debating "starting over" and using a plug-in Prius, Volt or Tesla battery pack, motor, charger, etc.

What system is easiest to "hack" in order to fit the components into my conversion? Feel free to speak at a highly technical level. I got that. I'm looking for the groups experience in the more common factory platforms and how they can be dissected and reused.

Thanks.
 

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Discussion Starter · #3 · (Edited)
The motor I currently have is a DC motor with a max input voltage of 144 (I think, it's ben buried in my shop for months and months).

I believe the Spark EV uses three 48v packs. I don't know how they are wired in the Spark, but I could wire them in series and get 144v. That would be a perfect match for my current motor and controller.

A Tesla battery pack is a bit more complicated, but I think it would work. Tesla uses 3.6v cells and they combine 74 cells in parallel into a module which should be ~21.6v. They have about 20 of these modules in series to get to ~450v. Getting this level of battery detail is convoluted as Tesla doesn't post the exact pack details. I think the information is generated by enthusiasts that have disassembled them personally. If the modules are even 25v each (hot off the charger), then I could run 5 of them and should have enough space in the MR2 for that. I guess I'd have a lot of spare modules. Maybe I could put a few packs in my Gem. :p

Trying to get the best options, learning from the group's experience, so I don't make the same mistakes as others might have.
 

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Discussion Starter · #5 ·
Forget about the motor voltage - You can't overvolt a DC motor
That's an interesting statement. If that is the case, why do the motor manufacturers label the motors with maximum voltage limits?

What you can do is over-rev and over-current one
Yes, that is the limiting factor. Internal wiring and bearing over race on the output shaft(s).

I have a Curtis controller... the ol' 1231C and it is rated for a maximum of 550 amps and 144 volts.
 

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Discussion Starter · #11 ·
The Spark is uncommon so there aren't many of them
Yes, that's the widget in the works. I've only found 6 of them in recent months on the various auto auction sites. Most of them are on the left coast. There are a couple in Houston (flooded of course), but I'm not sure that would be a wise candidate. Batteries don't care to be submerged in water and electric engine windings typically freeze up from rust. If I can get a wrecked/flooded car cheap enough, I'll consider it.

The Spark battery pack apparently changed significantly between the first version of the Spark (2014: cells by A123) and the second (2015: cells by LG Chem)
The facts I read were on the A123 pack. I didn't know they changed packs in mid-run. Coincidently, one of the models on auction is a 2014.
 

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Discussion Starter · #13 ·
I think I would be hesitant to put a lot of work into accommodating the A123 modules for the Spark, knowing that that they will always be rare, even compared to the LG modules for the Spark.
Lot's of great information and links. As much as I've dug up in various holes, there's always more available. Thanks for your effort.

Your point is quite valid. Why design battery boxes, wiring and connections for a battery pack that is going to be hard to source? I don't think Tesla is going away any time soon. There are dozens of cars available at auction. They are a good source for batteries, chargers/BMS and engines... if the system can be fully dissected and hacked apart. If it isn't already, it probably isn't far off.

I'll stick with Tesla auctions.
 

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Discussion Starter · #15 · (Edited)
Any progress on your build? My Spyder is waiting in lock-up for the event drivetrain sitting in my garage. Just another project I haven't enough time to crack on with.
Same here. Just last weekend my MR2 saw the light of day. Something it hasn't seen for probably 3-4 years. Everything is still in good shape. Spiders had taken over inside the car. It was a bit creepy to even sit inside it. I also noticed that the soft top is dry rotting around the top corners of the rear window glass. Sucks because I just had the top replaced before I stored it 6 or so years ago. That's a bit surprising as I stored it cleaned and treated and it's been under cover, in my shop, since then. Other than that, no further progress.

I also haven't secured any auctions for donor EV's. I've been watching Copart for months and months, but nothing won. The salvage cars are going for very high rates. I suspect shill bidding from the organizations selling them or some kind of "back end" reserves. I'm not in a big enough town to have anything local. My best bet in Houston or, less likely, New Orleans.

I envisaged a cassette case slotting in from underneath the car into the storage space like Riperton's bike battery or the Renault Fluence EV.
My desire/hope is to create a "standard" sized box that contains the batteries and can be lifted in and out from above with a forklift or engine crane. I could change battery technology fairly easy that way. I could also swap between two boxes easily. Have one as a charging spare to reduce potential charging delay. I haven't disassembled the car yet to determine the feasibility.

Fortunately the entire drivetrain with controller, charger, cooling pump etc is all mounted on a subframe that I can bolt into the engine bay.
I was going to put all "management" components in the front trunk. More as a "showcase" measure than a convenience factor. In fact, to do that will require a great inconvenience to me for installation.

I don't want to hijack your thread though. Apologies.
No, quite the opposite. I really value your comments and input. Please continue to share at your convenience.

Then you must split the pack.
I have no unreasonable aspirations for range in this car. Strictly for "fun runs" around town and maybe an occasional show. I have a Model S for more serious trips.

I believe you could fit 8 Tesla modules in that space which would be too much for your controller
By module, do you mean the 22.8v module? If I had 8 of those, I'd wire 6 of them up and look for 4 more for a second pack for the front trunk. :) Another factor driving Tesla modules is that I already have a Tesla HPWC installed in my garage. I also have a second one installed in my shop. It'd be nice to utilize my home charging infrastructure for both cars.

stacking Leaf modules vertically and side by side would give similar results with a simpler implementation method and more flexibility to achieve your required voltage.
Yes, the 7.4v modules would be much easier to place and would get me much closer to 144v output. I'd probably series 19 of them in my "battery module" box.

I look forward to both our progress.
I hope to learn from your experiences. I expect you will finish before I will.

What have you done for the more common accessories? A/C? Vacuum? Power steering? Dash gauges (Speedo, Gas - wired from SoC, RPM)?
 

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Discussion Starter · #16 · (Edited)
Since this was brought to mind (thanks tylerwatts), I did a bit more battery shopping. Just using eBay, Leaf and Tesla cells appear to be a rarity. I did find lots of Prius modules though. This one is a tested and warrantied module. 7.2v @ 6.5Ah. I would need 20 which would give me 144v and 130Ah. That converts to W=VA which is W=144x130 or 18.7Kw. 20 modules would be right at $1000 plus shipping.

The manufacturers curb weight for the MR2 is 2195 pounds. Assuming the weight remains similar (removal of engine, exhaust, fuel tank, etc. and addition of electric motor, batteries, etc.) and a general calculation of 250wh per mile (pack wh x wh/m), I should get 74 miles from a full charge. An 80% charge would be right at 60 miles. Almost exactly what I'm going for.

I can get the 3rd gen battery from the same group. It's a little more expensive at $1100 for 20 modules. They are both NiMH, so I'm not sure of the value of the newer modules.

I can get the Tesla Li-ion from EVWest, but it is very expensive. I would need 6 of those to get to about 136v (so I lose a little power) which would cost me $9480, but I get 31.8Kw of range. That's almost twice the range, but 10x the cost. If I could find Tesla modules for MUCH less, I would seriously consider them. Longevity isn't a discussion because I can replace the failed/worn NiMH 10x for each Li-ion and I doubt Li-ion has 10x the life.
 

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Discussion Starter · #18 · (Edited)
Don't forget that some vendors offer the 12S converted Tesla modules which are nominally 50V :cool:
Good information at that link, backed by forum user experience. Don't know how I missed that one.

Edison "has" the 12S modules for $1525. Since they are wired for 48v @ 5.4Kw, I could use 3 to get to 144v which would give me about 16Kwh of range. That's my desired minimum range at about 60 miles and is only $500 more for batteries over NiMH. That makes my "battery module" box pretty small. I could have two slots in my car and they would be in parallel. I could run them both or keep one as a spare to resolve range anxiety. There's a 99% chance that wherever one box got me, the other could get me home... assuming I didn't drive down a steep grade for most of my initial trip.

Edit: Forgot to multiply by 3 for the modules. $4575 in battery cost, not $1525. 4x the cost for basically the same performance (not accounting for battery weight or discharge rate) and the same range.
 
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