Engine CompartmentMain Battery Box100 GBS CellsSynchronous Belt DriveRear Hatch areaDifferential Pinion belt drive
OwnerBrian Hughes
Owner's Other EV1985 Toyota MR2
LocationSeattle, Washington United States map
Vehicle2004 Toyota xB
2004 Scion xB EV Conversion.
MotorAzure Dynamics/Solectria AC55 3-Phase AC
Solectria AC55 3 phase AC motor. Base mount. Air cooled. ANSI 32/4 or SAE "C" splined motor shaft.
DrivetrainSolectria AC55 motor
UMOC445TF Inverter
1984 Celica GTS Differential
Goodyear Eagle NRG "Blue" Synchronous Belt Drive
Driveshaft shop custom CV axles
ControllerAzure Dynamics/Solectria UMOC445TF
UMOC445TF inverter matched with the motor. 70kw/100hp. 360v maximum battery volts, 250A max motor/battery amps.
Batteries100 GBS 100ah, 320.00 Volt, Lithium Iron Phosphate
32kwh nominal lithuim battery pack. 100ea 100ah, 3.2v nominal GBS lithium iron manganese cells. Slightly higher energy density and slightly higher internal resistance vs other LiFEPO4 cells. Arranged in 6 banks of 12 and 2 banks of 14 below and behind rear passenger seat. Elithion Pro BMS.
System Voltage320 Volts
ChargerManzanita Micro PFC30
PFC 30 Serial number 81; though its guts have been completely updated.
HeaterCeramic core, 500W / 1KW dual setting. In original heater core location; integrated with dash controls.

No air conditioning; but provisions left to add it in the future.
DC/DC ConverterAzure Dynamics/Solectria 750W
Original guts were fried, reused original housing for looks but utilized newer single 600W DC/DC module along with internal contactor and care-and-feeding circuitry inside original housing.
InstrumentationAmmeter, Voltmeter, 12V Voltmeter.

Will be building telemetry gathering/display unit to collect and show information from Elithion BMS and UMOC inverter during driving.
Top Speed70 MPH (112 KPH)
I have reached 70mph; It might make 75 but that is about 6000 motor RPM and the AC55 won't make much torque past that speed.
Acceleration15 second 0-60 (roughly). Much faster than the MR2 was.
Range100 Miles (160 Kilometers)
100 mile design range at 55mph to 80% DOD.

I have proven out 90 miles prior to steering alignment and purchase of LRR tires; have done many drives into 60-70 mile territory without even breathing hard.
Watt Hours/Mile250 Wh/Mile
250wh/mile approximate battery to wheels efficiency at 55mph straight and level.
EV Miles
Start:148,048 Miles (238,209 Kilometers)
Current:181,500 Miles (292,033 Kilometers)
Total:33,452 Miles (53,824 Kilometers)
Seating Capacity4 adults
Curb Weight3,040 Pounds (1,381 Kilograms)
no passengers, cargo or gas. According to local truck scale.
TiresDunlop Enasave 01 A/S
15lbs/tire ; 51psi ; 1020lbs max weight

These are the OEM tires on rear axle of US market Mitsubishi iMIEV

Conversion Time1000hr approx.
Conversion Cost$6K for the car ; $20K for conversion roughly.
Additional FeaturesUnique direct drive design utilizing 1984 Toyota Celica GTS rear differential in the FRONT of the car. This differential picked because the ring and pinion are available in a very wide range of ratios and locking/limited slip carriers are also available, and the housing is compact and easy to mount in a custom application. Differential is driven via synchronous belt. This design allows for a very wide range of gear ratios from about 4:1 to over 10:1. Ideal gear ratio with the Solectria AC55/UMOC445TF seems to be about 5:1; current gear ratio in car is 4.8:1 consisting of 4.1:1 differential and 1.18:1 on belt.

I purchase the Solectria AC55, UMOC inverter, and some ancillary components at an abandoned storage auction. Got all the major components except breakout box there.

DC/DC converter is Solectria housing, but custom on the inside as the original internals were burned out due to OK design but poor execution on Solectria's part.

Inverter was working when came to me but I found several small problems upon internal inspection which I corrected before putting it into service.

Constructed a test-bench breakout box for maintenance purposes and constructed an integrated control box to interface the UMOC with the BMS, the car's electrical system, and a Gen 2 prius throttle pedal.

Rear suspension springs upgraded by fitting 2nd generation OEM scion xB springs. These fit just fine without any modifications and sit just about perfect with 700lbs of battery in the back when mated with the 1st generation TRD lowering springs on the front of the car.

Stock power brakes, vacuum supplied by Hella vane type vacuum pump and SSBC control relay and vacuum sensor. 10" length, 4" diameter sewer pipe vacuum reservoir. The brakes work great.

Original power steering rack replaced with manual steering rack from a 2000 Toyota echo. This is a bolt in replacement. Just be sure to get the boot and steering shaft as far as the universal joint if you do the same.

Car works fine without original ECU. Only issues are traction control, vsc, and check engine lights stay on. All Red warning lights go out, Speedometer still works as it takes signal from ABS system. All other warning lights and gauges are discrete wired (not CANBUS) so easy to override/hack in the future though I have not done it yet.

1000 miles driven since first drive June 27 2013;

So far so good all things considered.

Still working through various teething issues like changing to different synchronous belt type and gear ratio and adjusting the length of the drive axles, but the major design elements are all validated at this point.

Major remaining work is onboard computer software to monitor and log UMOC and Elithion BMS.

9000 mile update:

As of November 19, 2014: Car is running and in daily commute service owing to a new job a bit farther from home. Differential pinion bearing failed at mile 7500; I attribute this to its condition upon installation (sourced from pick and pull, unknown mileage, unrebuilt) and due to my having removed and improperly retorqued the pinion flange making the bearings too tight. However the side load from the belt drive may be a factor. Anyway, rebuilt the diff with solid bearing spacer instead of a crush sleeve to hopefully make it more robust. Batteries are still performing fine. At least one or two cells have substantially lower AH capacity than the others but this does not appear to be a degradation issue but a QC issue from the factory. I am getting about 60ah out of the weakest cell before it hits the steep part of its voltage discharge curve.

Best WH/Mile at 60mph in good driving conditions is about 220-225 meaning even with a low capacity cell I can reach 100 miles in a drive, which I have done several times.

15000 Mile Update:

May 22, 2015. No mechanical issues since prior update; rebuilt diff doing fine. I replaced one cell which was about 10-20% weaker by AH capacity than the others at about mile 11000. Cell was swollen visibly near top. All other cells seem to be doing fine. One BMS cell board failed after developing a problem that made the measured cell voltage drift, as if capacitively coupled. Also replaced. Still frequently making 80 mile drives ; I have not tried a 100 mile drive in about 6mos.

21000 mile update:
January 20, 2016. No mechanical issues since prior update. Car has been in use for 25 mile round trip commute for about 14 now and performing well. I recently went through and did a full checkout of the battery. This included putting a single-cell LiFePO4 charger on every cell. I did this to confirm good cell balance as I had been noticing that one particular cell always came up 'hot' first according to the BMS. As it turns out the pack was very well balanced. The single cell charger did not take more than a couple minutes on any cell to reach 3.6v, its cutoff voltage. I did replace a couple more misbehaving elithion cell boards and I removed, cleaned, and reinstalled some known high resistance bus bars which were getting bad enough to limit cold weather driveability. The major thing I did while I had everything apart was to redesign the upper battery box mounting points such that it is now on drawer tracks. This allows me to slide the upper box out of the way and lock it in position to make working on the lower battery bank much easier. I still have to undo some bolts and unplug a bunch of stuff, but I no longer need a shop crane to get into the lower battery box, so I can do it in about 30 minutes now instead of 2 hours. Weakest cell is #63. I can get about 24kwh out of the whole pack before it starts dropping off. That works out to roughly 66ah. These are 100ah cells so theoretically I should have another 14ah to go if most of them do meet spec. However even 24kwh in good weather that works out to just about 100 miles. I don't know how much capacity the rest of the pack would have left if I replaced that cell. It is not limiting my ability to use the car as I normally do so not doing anything about it for now. I don't think it has deteriorated, I think it has always been relatively lower capacity than the others.

April 2017 update:

Car is still in daily use. ~33500mi on conversion. No problems except one breakdown traced to bad connections in the motor encoder plug. Had to be towed home, but fixed by cleaning and re-seating plug. This era of solectria inverter has computer DB9 and Db25 plugs, not the best automotive all-weather connections. Most recent long drive was 96 miles with 1hr of L2 (+3kwh) charging part way. Current range (~50 degree weather, 30% rain 70% dry, moderately windy, 15 miles of stop and go) 85 miles. Cell 63 is still the weakest cell. One more elithion cell board is intermittent and should be replaced. I anticipate I would get back close to 100 mile range even under above not-terrible-but-not-ideal driving conditions if I were to replace that cell. LiFePo4 certainly beats the pants off of lead acid. (My prior EV conversion made 17K miles total on 2 lead acid packs) I recalibrated my amp sensor and now believe that actual battery-to-wheels efficiency is probably 15% higher wh/mile than previously figured, e.g. at 60mph good driving conditions in gets about 290 wh/mile. this would mean cell 63 has 80ah actual capacity, not 66ah as figured in last years update. Tires are almost worn out.

35000 mile update (Jul 2017):
Took battery apart for annual-ish check. cleaned and tightened more "hot" bus bars. Only found one completely loose screw. Found the metal retaining straps on one 12-cell bank had all broken. These were homemade straps I made when I repackaged the GBS cells which originally came in 4-cell blocks in 12 cell blocks instead. Some of the straps I made incorrectly and these are the ones that broke. Reassembled that bank. No evidence that the cells swelled appreciably. I did replace known-weak cell 63 which was the major goal of the overhaul. Like the original Cell 64 which was replaced early on, This one shows abnormal swelling around the positive terminal. I also replaced another failing elithion cell board and reassembled. Haven't re-tested range but if the new Cell 63 is at least par then this should get me back 5-10 miles of range. Note that while cells 63 and 64 are numerically adjacent, they were not sequential in terms of serial number nor part of the same original 4-cell block.

code by jerry