Published December 29, 2012: Updated August 12, 2014
Geo Metro EV Conversion Part II
For batteries, I was dead set on LiFePO4 batteries. I calculated that 100Ah cells would be sufficient to get me to and from work adequately but I sprung for the 160Ah cells just for the extra range.
A smart charger and BMS (battery management system) were absolutely necessary too. By going with a 72 volt system and using large 160Ah cells, I was able to keep the cost of the battery management system down yet still have a decent battery range. Lower battery voltage is also much safer to work on.
My greatest mistake on this car was that I didn’t buy my batteries, BMS and charger from a local distributor. I was seduced by the false promises and low prices of a dealer called EVLithium who is located in China.
His prices were so much lower that to me it was well worth the risk. But if something is too good to be true, it probably is. By the time the batteries eventually showed up, I ended up paying nearly the same price as the local dealer but with more headaches because of shipping delays, import fees and extra shipping costs that were not disclosed up front. After being without my hard-earned money for so long, I was very relieved that the shipment actually made it at all.
Sadly, the battery charger would not communicate with the BMS and in turn, it would not charge the batteries.
I made every attempt to RMA the charger back to EVLithium but they refused, insisting that it worked perfectly before it left the factory.
Lesson learned: If for no other reason, buy your hardware locally so you can have good and reliable tech support and a store-front that will accept defective product back.
I bought a new battery charger from Elcon out of California and 2 days later, my EV was up and running with a working, on-board battery charger.
Originally, I was going to put 13 of the 24 cells into a cage I fabricated under the rear set where the original gas tank used to reside. Just to get the car on the road, I temporarily set the remaining 11 batteries in the rear hatch-back area.
With almost no weight on the front tires, the Geo handled terribly. When driving faster than 40mph, I felt like any wrong turn would cause me to over-correct, sending me into a zigzag, following by several barrel rolls. Going back to the drawing board. I made some new battery boxes so I could mount 16 batteries in the front engine compartment and 8 in the box under the rear seat. All batteries fit better that way too.
After distributing the weight more evenly across the vehicle, the Geo handles much better. Batteries and all, this Geo is only 50 lbs heavier than the original, stock vehicle.
Here is the breakdown of the part costs of making the Geo EV.
Geo EV Parts List
|Motor||PMDC Motor 12-72V 15.4 hp cont, 38 hp pk||$625||Electric Motorsport|
|Controller||Alltrax SPM-72400 400 Amp||$517||Electric Motorsport|
|Contactor||Albright 12V SW180||$85||Electric Motorsport|
|Pot-box||Light Weight Pot Box||$65||Electric Motorsport|
|Fuse||400 Amp||$19||Electric Motorsport|
|DC-DC Converter||72 V to 13.8 VDC 30 Amp||$110||eBay|
|Shaft Adapter||Home-Made (used existing clutch disk), 7/8" shaft coupler and gusset.||$28||Metal Supply|
|Transmission Adapter||Home-Made with a 12" steel gusset.||$10||Metal Supply|
|BMS||Ligoo Battery Management System w/3" LCD screen||$500||China|
|Battery Charger||ELCON PFC1500 Charger 1.5kW||$480||Elcon|
|LiFePO4 Cells||160 Ah Winston LiFePO4 battery cells x24||$4200||China|
|Angle Iron||3/4 and 1" for battery boxes||$85||Metal Supply|
|LED light bulbs||indicator lights, turn signals and brake lights||$65||eBay|
|Battery cable||00 AWG red and black stranded copper||$80||eBay|
|Donor Vehicle||Paid $460, sold ICE parts||$380||KSL Classifieds|
|Misc Repairs||Tires, paint, wheel barrings, hatch back lift pistons, door handles.||$750||Misc|
You may be thinking that $8000 is a lot of money for a Geo Metro EV. That may be true but the majority of these parts (batteries included) will outlast the car itself. After several years, I can take these parts and put them into the next vehicle I decide to convert.
When you go to get the title changed on a converted vehicle, make double certain that you have all your proper documentation.
Sales recipes of all EV components
A signed letter from a certified mechanic, vouching that the vehicle has been converted and runs solely on battery-electric power.
If you don't look like you know what you are doing, it will raise more red flags in an already highly bureaucratic process and the less successful you will be at getting the title’s fuel-type changed to “Electric”.
With fuel type: Electric, exempts you from having to take an emissions test each year and also qualifies the vehicle for a clean-air sticker.
I took my Geo EV to the local county inspection center. My tires failed the safety for being too worn out. I was hoping to get some freeway drive time on them before replacing the tires so I could more precisely quantify any improvement switching to low-rolling resistance tires later on. Oh well.
I went down the street and bought some new all-season tires. 1 ½ hours later, with new tires, I passed the safety inspection.
My first commute to work in the Geo:
I was nervous taking it to work that first day. While I had calculated my range would be 50 miles at least, I didn’t really know for certain how it would perform. I was also nervous about using such a tiny motor to move a 4-passenger car at freeway speeds. I choose that motor based on modifying the car for maximum efficiency. Besides making it electric, I had yet to put in place any of the planned efficiency improving enhancements.
To my relief, the car drove at freeway speeds without any issues. With it being the middle of December, the frigid, winter air helped keep the motor cool too.
Permanent magnet motors have a maximum RPM that is voltage dependent. This means that the top speed is also voltage dependent. As it turns out, with a 72 volt battery pack and the gear ratio of a Geo Metro transmission, the top speed is no more than 85 mph. To date, the fastest I have driven it is 67 mph.
I drove the full 20 mile commute to work without any problems and only depleted the battery pack 33%. That means the max range is probably at least 60 miles.
Max Range Test:
I can claim that my electric car can go 60 miles on a charge but it's not a very credible statement until I actually drive 60 strait miles on a single charge.
Just like verifying the crush depth for a submarine. Before you can depend on something day in and day out, you need to put your money where you mouth is.
For my own comfort and peace of mind, I wanted to take the Geo EV out for true max range test. But before I did this I made some enhancements first.
Royal Purple SynchroMax in the gear box
Adding SynchroMax reduced the friction in the gear-box by 14%.
|Speed||Original 75W90 |
|Royal Purple |
|25 mph||15.5 Amps||14.5 Amps||1||06.45%|
|35 mph||22.3 Amps||18.4 Amps||3.9||17.49%|
|45 mph||28.2 Amps||23.3 Amps||4.9||17.38%|
|55 mph||33.1 Amps||28.2 Amps||4.9||14.80%|
|83 mph||50.0 Amps||43.8 Amps||6.2||12.40%|
This was measured with the wheels off the ground. It probably only translated into a 2-3% increase in actual battery range but every little bit helps.
Grill Block (front of car)
Undercarriage covers and grill-block reduced the 55 mph current draw another 20-25 amps (at 72 volts).
By reducing air and gear friction the motor load is reduced and the motor won't get as hot, not to mention it will extend the battery range.
76+ Miles: I drove from Kaysville, UT to the Salt Lake International Airport and then to the Home Depot in Layton, UT. Then to Centerville back to Layton back to Centerville and back to Kaysville. Then drove around city streets for another 4 miles.
According to Google maps I drove 80.5 miles. According to my odometer it was 76.6 miles. My State of Charge meter was completely down to 0%. Besides being able to make proven claims about battery range, I can now put my complete trust in the battery's State-Of-Charge meter.
Check out my Max Range Test here.
Since the last range test, I made another small improvement in reducing air friction. Rear-view mirror deletion.
I Removed those pesky, draggy, exterior rear-view mirrors
Installed an Interior Rear View Mirror
Mirror removal reduced the wind drag even further. Because of their more parabolic nature, these interior rear view mirrors actually have better visibility than the original stock mirrors.
I have yet to confirm if interior rear view mirrors are legal on Utah roads. I'm hanging onto the original ones just in case.
The parabolic mirrors are very good at eliminating blind spots but you lose your field of view in the process (everything looks too tiny). On 11/2013, I re-installed the external roadside mirror. Now there are two mirrors on the roadside and just the inside parabolic mirror on the curbside.