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
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
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
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

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.

55000 mile update (June 2019):
Still Alive! Still in service as my primary vehicle. I
haven't done much of any maintenance since last update. The
big issue right now is the car was side swiped by a ryder
rental truck while I was stopped at a light, and subsequently
totalled by the insurance company. Damage is isolated to
the drivers rear quarter panel, no unibody damage, doors
all open/close fine. I have bought the car back and am
planning to have it repaired and repainted, which is going
to be several thousand dollars on top of the insurance
settlement I received. To do the repairs I am going to have
to completely remove the battery pack and tow it to the auto
body shop.

I am planning on replacing 1 or 2 more cells with my last
spares as part of the overhaul process as well as address
more hot bus bars, but I may not see a huge bump in range as
a result, I think all the cells I am running now are within
about 5ah capacity of each other and aging fairly evenly,
so even if I replace the weakest one I may only get 5-8 miles
additional range.

Last full range test I did I got about 93 miles, at 75-80
degrees, level, freeway, light to moderate speed limit
traffic. So I've probably lost 10-15% range since peak
distance achieved (longest run on a single charge ever was
107 miles IIRC)

code by jerry