# 1986 Toyota MR2 EV Conversion



## gskellig (Feb 1, 2010)

*Your skill level with auto mechanics and fabrication*
None. But I have a few resources who are able to provide a lot of assistance.

*The range you are hoping to get (how many miles/charge)*
Depends on my budget. I'm _hoping_ to get around 50+

*What level of performance you are hoping to get*
It's a sportscar. I want it to stay that way. As good or better than ICE MR2.
Top speed probably doesn't need to be higher than ~70mph though.

*How much money you are willing to put into your project*
My plan is to sell my 2002 VW Golf to fund my EV project. (See below)

*What parts you've already considered, if any.*
I've looked at a lot of stuff. I haven't made any decisions. Probably a Warp 9" motor.

I'm a college student in Seattle, WA. This will be my first EV related project. My first auto/mechanical project and my first (major) electrical project so what the hell. I'm going to need a lot of help. I have friends/family members who I can get to help me with the mechanical/fabrication side of things, but I plan to learn a lot myself.

I have a 2002 VW golf with around 40,000 miles that I plan on selling to fund the bulk of my conversion. I don't _really_ need a car, so I can go without one for awhile. However I would like to be able to drive something for as long as possible. So I'm looking for ideas on how to keep my spending to a minimum as long as possible. My golf was given to me and I'd like to use it to fund an EV rather than driving a 29mpg car.

*The car:*
I was able to purchase a 1986 manual 5 speed MR2 with around 125,000 miles for $300. The engine is "dead" but everything else seems to be in great shape. I've always loved the older MR2's. I've done a lot of research on weight and aerodynamics and the MR2 passes with flying colors. Sure I could've gotten a Geo Metro for _maybe_ cheaper but I want my EV to be sexy.

*Batteries:*
Although my 50 mile range can be achieved in an MR2 with flooded lead acid. I like the pro's of lithium-ion, so if it can possibly fit in my budget I'd like to go that route.
On the other hand. I _may_ have an in with mastervolt. So if I can get some brand spanking new AGM's from them at a reduced cost, that is also an option. (No official numbers yet)

*Batteries:*
The attached spreadsheet is not completed but it'll give you an idea of what I'm considering. I'm fairly certain I'm forgetting some key pieces of information (Mr. Peukert might kick my ass).
Also, you can ignore the Mastervolt Lithium's. They retail at around $8000 each. Open office and Excel XML files included.

Brian Hughes has achieved 200 Wh/mi on his MR2 (also in Seattle). I'm doing my calculations based on 250 Wh/mi (You can change this in the spreadsheet).


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## samborambo (Aug 27, 2008)

gskellig said:


> I have a 2002 VW golf with around 40,000 miles that I plan on selling to fund the bulk of my conversion. I don't _really_ need a car, so I can go without one for awhile. However I would like to be able to drive something for as long as possible. So I'm looking for ideas on how to keep my spending to a minimum as long as possible. My golf was given to me and I'd like to use it to fund an EV rather than driving a 29mpg car.
> 
> *The car:*
> I was able to purchase a 1986 manual 5 speed MR2 with around 125,000 miles for $300. The engine is "dead" but everything else seems to be in great shape. I've always loved the older MR2's. I've done a lot of research on weight and aerodynamics and the MR2 passes with flying colors. Sure I could've gotten a Geo Metro for _maybe_ cheaper but I want my EV to be sexy.
> ...


Good choice on the MR2 - the first generation AW16 aren't my cup of tea but I bought an SW20 MR2 with a blown motor last year for about the same money. A warp 9 would probably serve you well - you're going to need about 15+kW of constant power for 70mph in an MR2. My MR2 is getting an AC induction motor, custom built controller and a pack of LiFePO4.

Unless the AGM cells fall off the back of a truck and into your hands, go LiFePO4. For the price, when you consider the cycle life, depth of discharge, etc lithium turns out cheaper. If you haven't considered the peukert constant for the LA cells (rule of thumb 1.1 for AGM, 1.3 for deep cycle), you're way off. The only downside to LiFePO4 is the significant cost of the BMS, or cell balancer. You'll find lots of opinions from various people on the best way to balance your cells. It's probably not as significant cost for you since your voltage will probably be 144VDC. It's proportionately more expensive for higher voltages like mine.

Woodsmith (on this forum) is in the middle of his conversion of an SW20 with DC motor, etc. He's documented his build thus far in a big long thread and maybe helpful as well. There's also another 3 SW20 conversions I know of here in New Zealand.

Work out the capacity of the LA cells you're considering based on a 1 hour rate. There's a significant difference. Also consider that AGM cells shouldn't be deeply discharged regularly so a depth of dischage (DOD) of 50% for regular range should be what you're aiming for. A daily commute should be less than 20% DOD. LiFePO4 on the other hand have very low internal resistance to the point where you neglect the peukert effect for <1C ( > 1 hour) discharge. The regular DOD for LiFePO4 cells can be 80% with a life of 2000 cycles (some datasheets say 3000). Is LA still cheaper? No way.

I have a spreadsheet I use for working out range and acceleration factoring in weight, wind drag, vehicle body, tyre resistance, etc. Let me know if you want it and I'll email it to you.

If you want comparable performance to the original non-turbo ICE, you'll struggle with a small pack. The large prismatic (cheap!) LiFePO4 cells are realistically limited to 3C discharge rate. For example, a 10kWh pack would be limited to ~27kW/35hp (30kW minus some volt drop in the cells). It's not directly comparable to the hp of the original ICE since the electric motor can put down maximum torque off the line. No matter what gearing you go with, if you don't have the power available from the cells you won't accelerate as fast.

Sam.


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## Lordwacky (Jan 28, 2009)

I'm currently converting an '87 mk1 MR2 using Lifepo batteries. My build is located in Enumclaw, which isn't far from you. Unfortunately I'm out of the country currently attending graduate school and I wasn't able to complete my build before I had to leave so it isn't on the road yet. But if you want to come and check out the car and get some ideas my father would be more then happy to show you around.

PM me if you are interested.

-Mike


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## madderscience (Jun 28, 2008)

You are welcome to come by and look at my car if you want. PM me or email me at the address on my website.

Brian Hughes


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