The First EVDrive-train™ Car Conversion Project – 2011

Written by admin. Posted in Build Diary

This project leverages off the known properties and traits of the classic and award winning best sports sedan in it’s class, the BMW 3-series sports car without compromising anything. In many ways the final converted car is better than the original gas/petrol burning original.

The vehicle was purchased and it’s performance was measured with 5 runs at Portland International Raceway drag strip on Aug 17, 2007. Major EV components were selected and the conversion officially began on Sept 1, 2007 when the gas engine was pulled.

This design does not rely on future technology. It is comprised of current production high performance EV components. The one element that has been missing from the performance electric market until recently: the battery.

Robust, high current cells that have the necessary power/weight ratio are now available. These batteries are less hazardous than the common Lithium Ion cells since they do not contain oxides. A good portion of the total effort for this project is the design and construction of the 15kWh power pack using a new generation of Lithium Ion cells from A123 systems. This is part of the secret sauce that makes this project possible.

Prototype motor choice was an AC induction type manufactured by Siemens of Germany. It is currently manufactured for city electric bus platforms at relatively low volumes. This brushless motor, it’s control and charger are all water cooled and share the original BMW’s cooling system. The motor is wound specifically for 700 Volt operation (rather than the more common 350 Volt) to extend the full torque level 2 times further up in RPM. This requires battery cells that can deliver both high electrical current and voltage without being overweight. (The production kits use our own custom motor with many superior features – see the new EVDrive-Train at the SEMA show this Nov. 2011)

The weight and the weight distribution is maintained after the conversion. The interior and trunk space will not be affected. Heating and air conditioning will also work in the same way except… the heat will come up quicker because there is no motor mass to warm up and the air conditioner runs independently with it’s own variable speed electric motor, both of which get their power from the high voltage battery pack.

The manual transmission will be used to allow setting the gear reduction ratio for selecting the desired torque applied to the rear wheels. Normally, it will be left in 2nd or 3rd gear that will handle the normal zero to highway speed range. On the track, 4th gear may be needed which may also be appropriate for longer trips on the freeway. First gear will now require a limited slip differential to help reduce spinning the tires off the line and on the inside wheel of a turn. Although I am keeping the manual clutch, with this electric drive system, the clutch will not be needed for starting or stopping! You just let off the brake and press on the “go” pedal. It will occasionally be used for shifting while in motion.

The charging is as simple as plugging in an extension cord. The length of time needed to charge a fully discharged pack is 4.5 hours when plugged into a 240VAC outlet fused similarly to a dryer outlet. The standard 120VAC outlet will also work but will be limited in power so will take longer. At current electricity rates, my 40 mile daily commute will cost $1.19 @ 11 cents/kWhr.

The Benefits

Not only will the car be fast and fun to drive, this concept also happens to be part of the solution to significantly reduce our use of fossil fuels. This is not just an increment in fuel mileage improvement, but ELIMINATION of the need for fuel within a 50 mile* range (90 mile range when rest of cells are installed into old gas take area)!

When power is taken from the electrical grid to charge this EV, the cost is 5.4 times less than the cost of gas needed to drive the same car the same distance at $4.00/gallon, which it just hit this month. This difference will grow larger without question in the near future.

The emission profile is significantly reduced, especially here in the Pacific NW where we have very little power generated from coal, coming instead from hydroelectric sources. We purchase renewable source power so none comes from any carbon emitting sources.

Side note, FYI: even if 100% of the power comes from a coal fired power plant, there is still 27% less CO2 produced compared with driving the same vehicle with fuel. Not only that, but the power consumed just to create each gallon of gas is enough power to drive this electric car ~20 Miles.

BTW, the global light crude oil production levels have been dropping since 2009 from existing well dropoff and a slowing discovery rate to make it up. It is becoming more expensive to replace the dropoff, much less increase production due to the non-linear demand growth. When the cost is high enough, the tar sands become more economical. The problem is, the tar sands require 2-4 times the energy to extract. That is very expensive and increases the CO2 emissions by that same rate.

With the energy used to free/extract this “molassis” crude oil, the BMW can be driven the complete 40 mile daily commute for every gallon transported and refined! It makes a lot more sense to use the energy directly for driving an electric vehicle because of the “windfall” difference in energy efficiency. Instead, use the natural gas to create power directly to the grid, delivered right to your house. With Time-Of-Use metering, the off-peak power is much lower cost, and there is ALWAYS excess capacity during the off-peak hours, while most people are sleeping.


Regarding the amortization of our PV array factored into the cost of driving my BMW, we have accounted for it.   In our case, the system cost after state and federal incentives was $4300 out of pocket cost.   To get the $10,000 grant money from the Energy Trust of Oregon, we are required to meet at least 75% solar exposure.  Since we had tall trees reducing the exposure below 60%, we needed to remove enough to get up to around 80%.  The harvest resulted in 3 full log truck loads of straight fir log sections that returned $4600, prior to taxes.  So our out of pocket expenses are already paid for.

We are currently on track to put greater that 5MWhr onto the grid this year (with a few weeks of best solar of the year we are at 4.7MWhr now).   This results in over 17k miles of driving my BMW per year, calculated by multiplying 3.5 (miles/kWhr) times kWhr (solar onto grid -which includes charging efficiency going into BMW pack.)


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