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Old 10-05-2016, 10:43 AM   #1 (permalink)
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Dreaming about an Insight-EV

Lately I've been thinking a lot about doing an EV conversion with my Insight, or a second Insight, and I've just started doing reading and research on it.

I was looking at battery weight:

Looking at the (old) Volt's pack, it appears to weigh about 400lbs and have a capacity of ~18.4kwh (0.046kwh/lb). The 24kwh Leaf pack, best I can tell, is ~650lbs (0.037kwh/lb). The 30kwh Leaf pack is ~700lbs (0.043kwh/lb). The new Bolt's pack is ~60kwh, and ~960lbs (0.063kwh/lb).

Given that these vehicles are much larger and heavier than an Insight-EV would be, I have only a vague idea how to estimate range, but I don't think I could get by with less than 150 miles of range, and 200 would be better; I regularly do 110+ miles of driving in a day.

The old Leaf pack is probably the easiest to acquire but (if the numbers I've found are correct) easily has the worst energy density. It might or might not give me my desired 150 miles of range Bolt packs will probably not start showing up for several years, but are far and above the best in terms of energy density.

~

The Insight weighs about 1850lbs. With engine, transmission and battery removed, it's down to about 1550lbs. I'm going to assume an electric motor and controller will weigh in the area of 100lbs (please correct me if this is way off). If I were to drop in a Leaf 30kwh pack, rated at 107 miles in the Leaf, I'd be up to around 2350lbs (give or take), which is about a thousand pounds lighter than the Leaf is.

The Leaf has a CdA of 6.94, whereas the Insight has a CdA of 5.00, 28% less. Given that once the ICE is gone, I can probably almost completely seal up the front of the car, and completely seal the bottom, I can optimistically get that 5.00 down to ~4.00, which is ~42% less drag. With this in mind, getting 150 miles out of a 30kwh pack seems pretty reasonable, especially if I drive with economy in mind.

~

Another factor I need to consider is size. Ideally, I'd like to pull the Insight's fuel tank and bolt an aluminum box under the car where it was, and pack it full of cells, with potentially some spillover into the Insight's cargo box or hatch area, which is approximately 4' x 4' with the existing IMA system removed. It's likely I could fit an existing leaf battery module whole into the hatch of the Insight intact, but that would be very inelegant.








~

I would imagine that simply taking all of the existing electronics out of the donor vehicle would be the easiest way to make this work, but I realize I could be seriously wrong. I have no experience with 3rd party motor controllers, what the advantages and disadvantages would be, but I'm very mechanically inclined, with a fair background in programming, and I'm certain I can eventually puzzle something out.

I'd love some feedback on the aspects of selecting the proper doner, with some ideas for mounting the battery and motor, and with how best to work out the electronics side.

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Old 10-05-2016, 11:14 AM   #2 (permalink)
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I wonder if the insight's motor could be used, though it's probably not big enough to sustain a decent speed. And it probably relies on the engine's crankshaft to support it.

Evmetro is your guy to talk to. Similar sized cars and all.

Moving the entire drivetrain/battery/etc out of a factory EV would probably be a PITA. Mainly because of the stupid amount of wires you'll have to move over and incorporate in to your vehicle - and get 100% right - to get it to work.

Not sure there's enough room to cram 150+ miles worth of batteries in to such a small car. Again, check with Evmetro.

I think the Insight would make a great platform for a conversion, though.
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Old 10-05-2016, 02:06 PM   #3 (permalink)
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Here is a guy who has done a good amount of work on EVs and an Insight it seems.

Gary Graunke's Honda Insight Out-a-sight

Quote:
At 20-25 mph, ~9.7 mi/kwh, At 35 mph, ~9.46 mi/kwh, At 45 mph, ~8.69 mi/kwh, At 50 mph, ~5.39 mi/kwh (very preliminary data). City driving (stops), ~6.84 mi/kwh. Regenerative braking.
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Old 10-05-2016, 04:26 PM   #4 (permalink)
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What a sharp drop at 50mph. If I assume I'll get his efficiency of 45mph, the Leaf's 30kwh battery (sans 2-3kwh) could take me... between 225 and 250 miles?
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Old 10-13-2016, 09:32 PM   #5 (permalink)
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Doing a bit of math, I realized that electricity may actually be more expensive per mile. With my 90 day average of about 80mpg, and gasoline at $2.20, I'm paying about 2.75 cents per mile.

The Nissan Leaf is EPA rated for ~30kwh/100miles. 1kwh costs about 17 cents here (24/7), which would make driving a Leaf ~5.1 cents per mile. Even if a Leaf drivetrain in my Insight was good for 33% extra range, and I got 50% more than that by driving technique alone (similar to what I'm getting in my Insight), which I think is being very generous, I'd still be at ~2.6 cents per mile on electricity. Add a 10% AC-DC conversion loss and we're at 2.8-2.9 cents per mile. Certainly I wouldn't have a 2.5 quart oil change every 10,000 miles, but the weight of the batteries would probably make me go through tires more quickly.
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Old 10-14-2016, 06:23 PM   #6 (permalink)
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Given the known differences in Weight , Aerodynamics ,etc.
Between the Leaf & Gen1 Insight:

no wind , flat level ground , Standard Temperature , etc.

Including the rolling resistance effects of a 1550lbs + 750Lbs = ~2,300 Lbs BEV-Insight Conversion.

Including 250Watts of DC-DC 12v system load

Includes if motor controller and motor combined are ~90% efficient .. ie what the batteries would have to put out.

Nissan Leaf (~roughly):
~11.95kw to sustain 60MPH @90%Eff = ~13.28
~7.9kw to sustain 50MPH @90%Eff = ~8.78
~4.97kw to sustain 40MPH @90%Eff = ~5.52
~2.93kw to sustain 30MPH @90%Eff = ~3.25

The Gen1 Insight Need to supply to wheels:
~8.80kw to sustain 60MPH @90%Eff = ~9.77 = ~36% further than Leaf per kwh
~5.95kw to sustain 50MPH @90%Eff = ~6.61 = ~33% further than leaf per kwh
~3.87kw to sustain 40MPH @90%Eff = ~4.3 = ~28% further than leaf per kwh
~2.42kw to sustain 30MPH @90%Eff = ~2.69 = ~21% further than leaf per kwh

I don't know the average ICE efficiency you get when you get that 80 MPG ... but here are some comparisons.

Worst case ... if you were getting 100% ICE efficiency ... you would be getting about ~2.3 miles per kwh.

At the highest ever quoted Gen1 Insight ICE modeled efficiency .. form EPA420-D-04-002 ... peak LeanBurn at ~48% ... you would be getting .. ~4.7 miles per kwh.

At 35% ICE efficiency ... you would be getting ~6.5 miles per kwh.

Although your ~80MPG rate of energy per mile would likely decrease with the additional vehicle weight ... you could test by driving around with about ~450Lbs of passenger+cargo weight.

However ... I think if you continued the same driving habits , and conditions ... over 5 miles per kwh of battery is a safe / conservative estimate .. and up around ~6 miles per kwh of battery is perhaps a bit optimistic.

It is also a good idea to include some safety margin in your battery pack design ... for cold weather .. for unexpected detours ... etc .. **** happens.

I would recommend about a ~25% additional safety buffer margin.

For 150 miles .. that would mean you will want a minimum of about usable 30kwh.

For 200 miles ... I would estimate you will want a minimum of about usable 40kwh.

If you can to opportunistic charging ... Than you could vastly reduce the size of your needed usable kwh of battery pack ... sometimes by 1/2 , depending on your situation.

Looking at acceleration rates for the ~2300 Lbs Converted BEV-Insight.
3 m/s^2 rate of acceleration 0-60 in about ~9s ... would need about ~60kw for those ~9s.

I would recommend Batteries , controller, motor should all have a ~10second Max rating of at least (minimum) +25% .. or ~75kw peak ~10second Surge rating.

I would also recommend not going any lower than about ~30 kw sustained / continuous duty rated equipment .. that should still give you a little safety margin for daily non-flat conditions.

A good bit of the Leaf Pack weight is the structure the way Nissan did it ... You can probably package significantly better ... Each Leaf 4 cell subpack module comes in at about ~125 wh/kg ... 30kwh worth of those modules weighs .. about ~240 kg (~528Lbs) .. +you will need to add additional weight to that for connections , structure , etc .. of a final complete battery pack.

Leaf packs are nicely .. fairly easily available .. and nicely low in $/kwh ... but if you are willing to pay more $/kwh ... and do more hunting for the less commonly available .. the Tesla packs have far more wh/kg .. ie .. same kwh weigh less:

For example .. Tesla Cells come in at about ~265 wh/kg ... a 30kwh pack would be about ~114kg (251lbs) worth of batteries ... +you will need to add additional weight for the connections , structure, etc ... of a final complete battery pack.

I would also strong recommend testing any cells you get ... it is only the 'usable' capacity that is of value to you .. if some old junk yard Leaf cells only give you ~120wh/kg , than that is what they are ... and if some old junk yard TeslaModelS only gives you about ~250wh/kg output from it's cells .. than that's what they are ... don't just assume they will be a 100% perfect fit to published specs ... or to the test results others have gotten.
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Old 10-14-2016, 06:51 PM   #7 (permalink)
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Hugely useful post, thank you IamIan.

I also need to factor in weather / temperature. If I'm going to be using an EV when it's 20-30 degrees below zero, I'm definitely going to be using a heater, and range will already be reduced by virtue of lower temperatures.

Is there any reason I shouldn't have the battery modules split, to help distribute weight? A double 24kwh Leaf pack could provide what I need, but I don't think I'd want all of that weight in the back.
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Old 10-14-2016, 07:14 PM   #8 (permalink)
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The one true g1 insight lipo conversion I am aware of was good for 160wthr/mile at 60mph, I have no doubt an Ac conversion can do similar ly
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Old 10-14-2016, 08:15 PM   #9 (permalink)
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Something you need to think about is that IIRC the Insight is rated to handle only 350 lbs of passenger & cargo weight. That's 2200 lbs, and you'd be going a couple of hundred pounds over that before you add the driver. You've also got fore-aft balance to consider. Best case, I think you'll need to look at suspension upgrades.
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Old 10-14-2016, 08:20 PM   #10 (permalink)
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As-is, I've towed 1000-1500lbs behind it (~100lbs tongue) with 2-300lbs of cargo in the hatch, myself, my wife, our sheltie and her mother's border collie in it. The car was sitting pretty low, but handling was still very good and braking was fine even going down some pretty steep mountains. I'm thinking pulling 350lbs of ICE and IMA related stuff out and replacing them with 6-700lbs of EV gear won't be a problem.

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