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2000 Miata with batteries from a Leaf

20251 Views 26 Replies 8 Participants Last post by  SirAri
When I saw that I could get 24 kW of batteries from a wrecked Leaf cheap that inspired me to revive my old conversion, a 1990 VW Cabriolet www.evalbum.com/1588. Thinking more about it I decided I wanted a car that I liked better, was in better shape, and still had the A/C intact.

So here is the plan, recover the parts from the cabriolet and put them in a 2000 Miata with an upgrade to lithium.

Here is what I have:

2000 Mazda Miata
battery pack from a 2013 Nissan Leaf
Impulse 9 electric motor
Logisystem controller
PFC-20 charger
Iota DLS 45 DC/DC converter
vacuum pump
various other cables, gauges, etc.
ACT Prolite Flywheel (9 lbs.)
ACT ZM-2 pressure plate and clutch disk

I have a adapter plate, spacer and hub on the way from Electric Car Parts (I think I may have gotten the last one, they say they are no longer making them)
I plan to get a Benling electric powered scroll A/C compressor.

The controller I have is rated to 144V. I plan to wire the batteries 16s3p, since there are 48 battery modules that are nominally 7.5V that will be 120V and 180 Ah, however the batteries actually charge safely to 8.1V that will approach 130V. I am considering sourcing 6 more to go to 18s3p to get more voltage, but I am not sure the extra $600 is worth it and I don't know if the mismatched capacities of the batteries is a good idea with keeping them balanced.

I checked all of the batteries from the pack I got and they were all within 0.01V and have stayed that way for over a month, losing very little charge while sitting. I plan on using MK3x12 regulators from Manzanita Micro because they will talk right to my charger.

My commute is only about 3 miles, but I figure I am good for at least 50 miles with this setup, which will be fine. My last car was clutchless, but I'm going with the clutch this time. I think acceleration should be good since I can use first, which I never did before (too long to shift to 2nd without the clutch).

Any thoughts especially about more voltage, the scroll compressor, or the regulators?
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Discussion Starter · #3 ·
Thanks Wolf. I see you have the 150V series and then you will parallel 4 of those together. I was planning on putting sets of 3 modules in parallel and then connecting those in series. Any advantage or disadvantage to the different configurations? I was hoping that mine would allow easier monitoring since I will essentially have 32 180 Ah batteries. You will have 160 (?) to monitor, right? Looks like you are reusing the wires from the original pack though.
 

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I did not want to parallel modules, and then wire them in series, due to the potential of one of the cells shorting.

I am sure Nissan has already did the math and has figured out that the 2s2p module can handle the energy from one cell shorting into the other cell.

I doubt it could handle the energy of 3 or 5 cells shorted into one cell.


The other advantage is redundancy, if one of the four 150V packs has a problem, the power controller will disconnect it from the main DC bus, and I can still make it home on the other three. ;)

On my lead acid pack I had a battery connector fail (cracked), but I was still able to make it back home on the other working half of the battery pack. 24 12V batteries, two parallel strings of 12 in series.

Same with the power train, I have smoked a motor controller and still made it back home on the other one. And have broke a belt a couple of times, but I can always make it back home to make repairs. ;D
 

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Discussion Starter · #5 ·
Engine out and sold. Need to fit 36 battery modules in here along with the electric motor:



Also dropped the rear end to remove the fuel tank to make space for batteries. I've got a piece of 5/8 HDPE that should make a nice shelf to hold the other 12 battery modules where the fuel tank use to be:

 

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Engine out and sold.
Did you weigh it, so you know how the weight after conversion will compare?

Need to fit 36 battery modules in here along with the electric motor...
Each bare Leaf module (using the specs from Electric Vehicle Wiki) has a volume of 2.36 litres or 0.083 cubic feet. 36 of them would then be 85 litres (or 3.0 cubic feet). That wouldn't be a problem without the motor, but with the motor and the controller that's a tight squeeze... especially with the extra volume needed to assemble and house the pack, and the inconveniently rigid module dimensions.

36 modules will weigh 137 kg (310 lb)... plus the box they're in, plus wiring, plus the 60 kg (133 pound) motor, plus the controller. It would be nice if more of the modules could go in the back, for the sake of balance and traction; that would presumably intrude on the trunk. It was such a well-balanced car before the conversion...

If you follow the WolfTronix approach you would have three 16-module packs, so a 32-module front pack (and 16-module rear) would make sense.
 

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Discussion Starter · #8 ·
Did you weigh it, so you know how the weight after conversion will compare?
I have thought about this a bit. I do want to try and maintain the balance.
I didn't weigh the engine, but according to this site http://www.motoiq.com/MagazineArticles/ID/1645/Project-Miatabusa-Part-3--Let-the-Weight-Weenieing-Begin.aspx
the engine, alternator, and power steering pump, which will all be gone are 296 lbs. My calculation of 36 battery modules from that site was 301.6 lbs. Since I am also loosing the starter, that is just about a direct swap.

I have the adapter plate and spacer at about 12 lbs and that is about the difference in weight between my old flywheel and the 9 lb one I am using, so also a wash.

The 12 batteries in the back plus the shelf I made for them are about 120 lbs (that 5/8 HDPE is heavy). A full fuel tank (12.7 gallons at 6.3 lbs per gallon= 80 lbs) is about 100 lbs. Add the charger in the trunk and we are about equal.

Now we still have the motor, controller, vacuum pump, wires, and boxes to go up front. The impulse 9 is 129 lbs, plus all the other stuff would probably be about 180 lbs total (ballpark). I did lose the radiator and all the fluids, estimate about 30 lbs.

So, overall, I think I will be gaining about 150 lbs total plus another 40-50 for the aftermarket roll bar, which helps event the distribution front to back. Just a bit more up front.

Wolf's set up requires too many points to monitor, it would be a fortune in BSM. That is why I am going with one series string of 16 batteries made up of 3 modules in parallel, 32 points to monitor. I think Wolf is making his own BSM, so he can get away with it. :cool:That is beyond me.:confused:

Given that, I need 2 sets of 18 modules and 1 of 12 to work with the BSM from Manzanita Micro. So I as still thinking about trying to get 6 more modules moved to the back, that would even up the weight almost perfectly, but they won't fit in the fuel tank space, they would need to be in the trunk.
 

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I'm glad to see that weight and balance are getting suitable attention. One thing to watch for is that I see a lot of conversions piling battery boxes far forward under the hood, due to a lack of space. That 296 pound engine is centred well behind the front axle, so if the batteries spill forward as the packaging problems are worked out, the mass distribution could be further forward than the total weight "under the hood" would suggest.

If you really want to keep track of this, pick a reference point and keep a total (I would use a spreadsheet) of the moment for each component - "moment" is the weight multiplied by the distance from the reference. A reference point can be any sensible fixed location, such as an axle, or a bumper; the advantage of an axle is that it is a well-defined point along the car which doesn't get moved in body modifications, while the advantage of a bumper is that all distances from it will be positive (since there are not components on both sides of it). Divide total moment by total weight, and you have the distance to the centre of mass (centre of gravity) of the components. In this case, I would use the rear axle. This is normal practice for race car setup and aircraft loading. I haven't seen anyone do this in this forum (but I have only read a very small fraction of the build threads), but I wouldn't be surprised if there are some small cars with disturbing bias toward the front.
 

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I didn't weigh the engine, but according to this site http://www.motoiq.com/MagazineArticles/ID/1645/Project-Miatabusa-Part-3--Let-the-Weight-Weenieing-Begin.aspx
the engine, alternator, and power steering pump, which will all be gone...
The engine-driven power steering pump will be gone, but won't it be replaced by at least a comparable mass of electrically-powered power steering pump? You can de-power the rack (online article about this from Flyin' Miata), but the steering effort will likely be too high, especially with increased load on the front axle. A manual rack can be substituted, with a slower ratio to make it easier, at the expense of quick steering (and still more work, although more manageable).
 

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The 12 batteries in the back plus the shelf I made for them are about 120 lbs (that 5/8 HDPE is heavy). A full fuel tank (12.7 gallons at 6.3 lbs per gallon= 80 lbs) is about 100 lbs. Add the charger in the trunk and we are about equal.
Have I missed something, or is the electric setup 20 pounds heavier, plus the charger... not equal to the original?

I don't think I would use a solid horizontal panel of HDPE structurally. Not only is it dense, it's not very stiff and will probably sag in the long run if significantly loaded.
 

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Discussion Starter · #12 ·
Thanks for your input Brian, it's good to have someone critique this project.

Have I missed something, or is the electric setup 20 pounds heavier, plus the charger... not equal to the original?
You're right, that is heavier in the back. At least that will even up the front to back ratio :D.
I don't think I would use a solid horizontal panel of HDPE structurally. Not only is it dense, it's not very still and will probably sag in the long run if significantly loaded.
I have the HDPE in there already and am going to support it with a piece of angle iron to prevent sag. It also rests on part of the backend, so that should keep it flat.
You can de-power the rack (online article about this from Flyin' Miata), but the steering effort will likely be too high, especially with increased load on the front axle.
I am going with the flying miata depowered steering rack. I talked to some guys who race these (tho ones who bought my engine) and they said it is no problem. We'll see. I went without power steering in my last conversion and it was a bit heavy in the parking lot, but no problem otherwise. If it is too bad I will have to spring for the manual rack, but those are rare and $$$ on these cars for some reason.

I've been thinking more about my battery layout and also reconsidering my BMS. I was going to go with the manzanita micro MK3x12 with medium dissipation (not sure how much that is but the regular is 60 mA, so medium must be more than that), because I will only need 3 of them, but now I am considering just springing for the MK3x8. That will be more money because they cost more and I need 4 of them. Then I could put 24 modules in front, 12 where the fuel tank was, and 12 in the trunk. Now we are starting to get heavy in the back though, might move the charger up front. The 12 volt battery is also in the back on these, so I would probably bring it up front too. I think i"ll try that reference point method.

The other thing about the MK3x8 regulators is that they can dissipate 2.5 amps. Since my paralleled batteries will be 180 Ah I might need that, although I have read that the leaf batteries stay pretty balanced.

Anyone have any thoughts on whether I need to be able to dissipate that much to charge at a decent rate and keep these balanced?
 

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Discussion Starter · #13 ·
Got the motor in this past weekend. I used a motor mount from Canadian EV and bolted it to the frame with a polyurethane motor mount set from energy suspention parts between it and the frame. This setup put everything in exactly the right place. Here are some pictures.

I smoothed out the frame with a little JB Weld first so that the polyurethane bushings would have more surface to contact:


Here are the bushings in place:


Bottom half of the mount with new holes drilled to accept the 5" bolt extending to the bottom of the frame.:


Finally, with the motor in place:


This puts the frame that supports the transmission 66mm above the support beams, which is exactly in the middle of the range (60-72). I wish I could say I planned it that perfectly, but mostly luck.
 

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Discussion Starter · #14 ·
Ran the motor last week to test it out in the car. Wheels spun in first gear. Tried shifting to second and got a terrible grinding. I thought the clutch was not fully disengaging and spend a lot of time trying to adjust it. Ended up having to take the motor back out. Turns out the pressure from the clutch was pushing the coupler back into the aluminum plate.


It was installed with clearance. Here you can see the aluminum ground off by the coupler.

Got some machine bushings that fit around the shaft and contacted the rear motor bearing. I used 3 to get the spacing back to where it needed to be and keep it there. The key alone was not enough to keep it from moving.
 

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Discussion Starter · #15 · (Edited)
Each bare Leaf module (using the specs from Electric Vehicle Wiki) has a volume of 2.36 litres or 0.083 cubic feet. 36 of them would then be 85 litres (or 3.0 cubic feet). That wouldn't be a problem without the motor, but with the motor and the controller that's a tight squeeze... especially with the extra volume needed to assemble and house the pack, and the inconveniently rigid module dimensions.
Now that the motor is in, starting on the battery racks for the front. As Brian suggests, the space up front is limiting. I was thinking of 36 up front, but it looks like I'll be able to get 24 in front and the other 24 need to go in back. Here is the layout for the front racks. Using slotted steel to hold the racks from the original pack.

The original racks are 4 long, so they need to be cut up. Here are 2 plus the controller in the place it will sit.
 

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Discussion Starter · #16 ·
My last conversion did not have A/C. Even though both are convertibles, sometimes it is just too hot in Florida. Here is the compressor mounted using some L-brackets bolted to the frame. I got a pulley that will go on the tail shaft from EV West.
 

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Discussion Starter · #17 ·
Here are the rear packs. The first is where the fuel tank was and the second is in the trunk.

Tight fit in the space where the fuel tank was:


I cut 5/16 threaded rod to make the bolts to hold these down. Much cheaper and easier to get than 9" bolts. Just had to use a die to get the threads clean after cutting. Also, the threads on this rod are not that great to begin with.



The trunk pack is resting on the rim around the spare tire well as well as on some slotted steel:



1/4" thick x 1" copper bus bars to connect batteries and 1/8" to parallel the modules:

 

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Discussion Starter · #18 ·
To keep form driving off while still plugged into the charger I installed a push button that will sense when the charger door (gas cap) is open. This is wired to a relay that will close when the door is shut and the key is turned to accessory. That relay closes one of the contactors.

Hole for button:


Button installed. The screw head was just the right thickness to depress the button when the door is closed:



Virtually invisible once installed:

 

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Discussion Starter · #20 ·
Almost done with the rear wiring. The colored wires are for the BMS. No room for the vacuum pump up front, so it is in the trunk with a long vacuum hose to the front. The charger will also go back here on the left side of the trunk.



Had to completely finish the wiring for this pack and connect it up to the contractors and controller, because the 2nd front pack will limit access to this one.

 
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