# 91 honda civic ev conversion



## luke woods (Dec 2, 2013)

I have a 91 Honda civic and would like to make it an ev. I have been reading up on ev conversions but would like any feedback about this vehicle, what motor to use, batteries, etc...
I drive about 130 miles round trip every day, and there are quite a few hills. It's highway and freeway most of the way. I need to drive at least 65 MPH, more would be good, I like overkill. I am worried that it is just too far on a charge. I would charge it while I work, so it would have a good 8 hours there then at home as well. 
I am somewhat mechanically inclined, and am going to DIY as much as possible, and I don't have much money to spend. I do not know much about electrical systems, but I am studying up on that. 
Also wondering if there is a way to charge while driving? Some kind of way to use an alternator or generator? If anything, at least to get a few more miles.
Any info is much appreciated.


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## jonescg (Nov 3, 2010)

Hi Luke,

Great choice of car, and one for which there are a few examples of well-built conversions. 

Your range of 130 miles (210 km) at 65 mph (105 km/h) is achievable, but it won't be cheap.

You will need the most energy dense battery you can possibly afford. Assuming 150 Wh/km (which is pretty efficient motoring) you will need about 32 kWh. If we factor the whole 80% DOD in there, you will need about 37 kwh. The best NMC chemistry you can find offers about 175 Wh/kg, so that means a good 220 kg worth of battery. 

Provided you did away with the rear seats in your car, you can fit a battery this size behind the seats and provided you have a sub-80 kg motor-transmission up the front you won't be too far overweight. The motor will need to be very efficient too. 

All up, you're looking at a $60,000 conversion. Batteries are about $40,000 of that, and the controller-motor-transmission is easily $20k. Since you need efficiency and low weight, it would be best to avoid a DC setup.

Sorry to scare you off, but what you describe pretty much describes exactly what I hope to achieve with my Honda CRX conversion late next year, or whenever I can afford it.

Best of luck with it!

Chris


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## madderscience (Jun 28, 2008)

If you can RELY on charging at work then you don't need 130 miles of useable range. Even at level 1 (110V) charging you can recover about 30-40 miles of range in an 8 hour workday. this would mean you need about 90 to 100 miles of range. Round it off to 100 for sake of argument.

I just recently finished a 2004 scion xB conversion with 32kwh of lithium. The design range is 100 miles, which assumes 250wh/miile to 80% dod. I have driven it enough on the highway at ~60mph to verify the 250wh/mile number with reasonable confidence for my car, and I've gone 90 miles (max) so far and ~80 miles many times now, including in (seattle) cold, rain, and wind.

The prior poster suggested 150wh/km which is 240wh/mile so pretty close to my estimate, however the Civic is a more aerodynamic and lighter vehicle. It is probably safe to figure 200wh/mile if you set it up right including LRR tires, alignment, perhaps lowering and mild fairings like belly pan, etc. and you aren't driving into a tall headwind or over mountain passes or otherwise horrible conditions. If you do, add 10-20% depending on how extreme it is. Rolling hills will average out and not affect overall efficiency much (you get to coast down the other side).

At 200wh/mile with 25kwh of usable battery (32kwh nominal, 320v, 100ah), You are looking at 125 miles of range. With LiFePO4 you are looking at about 700lbs of battery to do that (that is about what mine weighs). I carried over 1200lbs of lead acid in my old 85 MR2 conversion, so carrying the weight is certainly possible though PP is right it will probably eat the back seat and a lot of cargo space. If you went to 130ah the battery would weigh closer to 1000lbs but you would get another 40 miles of range so.

If you build a car with this kind of range, you should make sure it is J1772 compatible (presuming you are US based). This will allow you to use public charging infrastructure, so if for example something happens and you need to detour or drive beyond your range you can charge up without knocking on somebody's door and asking for a plug. It adds a little, but not much, to the overall cost. At this point, If you are in or near any major metro area of the US there should be at least a few such charging stations near your route.

I spent about $25K on my entire conversion (the 'garage' won't let you put numbers over 10K in for the build cost for some reason) and about half that was battery. I did get a reasonably good deal on new surplus cells, but even full retail isn't that much worse. I had a couple savings here and there but my chassis probably cost more than yours would, so in the ballpark of $30K is probably more like it for cost for such a car.

Still not exactly cheap, but half a tesla (not including your time cost)


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## tylerwatts (Feb 9, 2012)

Luke 
Work out your performance, range and budget requirements. With a good charger and smaller pack you could easily make the journey to work with some spare charge and recharge before turning home again. That would reduce battery costs and weight and improve efficiency and even mean you could use a DC setup possibly. Budget will dictate alot though so give us a ballpark target to make some calcs again.


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