Lexus GS450h Inverter
The Lexus GS450h VCU is an open source project to repurpose 2006-2012 Lexus GS450h inverters for DIY EV use. It consists of a circuit board and programming that communicates with the original logic board in the inverter and allows independent control of it without communicating with a GS450h ECU.
Note that the Toyota Camry hybrid (US market) uses a similar inverter with the same logic board, which is functionally identical to the GS450h unit.
The Lexus GS450h is a hybrid vehicle. Their inverters are suitable and attractive for DIY EVs because of:
- Good availability and price - an inverter and "transmission" can generally be purchased for less than £/€1000.
- Durability. Toyota engineers appear to have made the inverters foolproof, many inputs and outputs gracefully handle fault conditions.
- Respectable performance. Rated for a combined 250kW output.
- Ease of repurposing. Emulating the original ECU seems reasonably feasible. The transmission is a similar size and layout to many RWD transmissions.
The Lexus GS450h (2006-2012 model years) has a variety of useful components inside the inverter package:
- 2 high power inverters, for the 2 motors MG1 capable of handling X(?) amps, and MG2 capable of handling Y(?) amps.
- A boost module to boost the 288v battery pack up to 650v
A buck/boost converter lives within the inverter housing, originally this is used to step up the 288V battery pack in the GS450h to the 650V for use in the inverter. For those using a 600+V battery pack, this converter can be used to step the voltage down to a more reasonable level to interface with charfgers, DCDC converters, heaters, AC compressors, and other components which can be found in "regular" EV's (Tesla, Leaf, Volt, etc).
This unit is rated at 30kW, making it unsuitable for traction power, but good for auxiliary devices.
Details on how to control the converter are here: https://openinverter.org/forum/viewtopic.php?f=14&t=538
The transmission contains two "Motor-Generator" units. MG1 sits at the front of the transmission, and interfaces with the internal combustion engine through a planetary gear set. For this reason, to obtain torque from MG1, the input shaft of the transmission must be locked in place. This is usually done using a splined coupler, which is then welded onto the transmission front mount.
The input shaft on the transmission has 21 splines, with a 28mm major diameter. It is believed that there are several Toyota clutches which will have this in their centre. The original GS450h flywheel and coupler also contains the appropriate slined centre, of course.
The fluid fill port is the banjo bolt for the upper transmission cooler hose. The specified fluid is "Toyota WS" ATF.
It is a good idea to replace the two bearings in the electric oil pump before fitting a used transmission. There is a guide here. Bearing part numbers are 61900-2Z and 608-2Z, you will need one of each.
The shift position lever on the right-hand side of the transmission engages the parking pawl when in the "all-the-way-back" position. All other positions disengage this pawl. The R, N, D, M positions only affect the output of the shift position sensor.
Note the following when purchasing the transmission:
- It is recommended to purchase one which has the electric oil pump fitted - these are a costly item as the bearings in them often fail, in some cases they cost more than the transmission.
- It is recommended to purchase a transmission which includes the wiring harness, or at least off-cuts of the connectors. Some connectors may be unavailable for purchase. There is a thread here which covers the connectors on this transmission.
Overall height (oil pan to top of bellhousing) is 39cm. Bell housing is full height, i.e. 39cm diameter, when the transmission is sitting on its oil pan (as it is on my bench), the bellhousing still just about touches the bench.
Widest point is 40cm, includes a bump for a starter motor which I don't believe the GS450h even has. Likely leftover to mate with the 2GR engine.
Overall length including tailshaft, output flange, and pilot shaft, is 82cm.
Transmission is tapered quite heavily, the width and height is closer to 25cm after the bellhousing, but hard to gauge due to various outcropping parts (motor cables, oil pump, PRNDL selector, etc)
Wiring Harness Connectors
Here are a list of connectors required for the GS450h transmission & inverter if you need/wish to build the harness for your build. (It is a good idea to find components with at least the connectors to build on. As some of the connectors are impossible to obtain)
|Inverter interface connector (A62)||90980–12630||Black connector on the side of the inverter. This connector is not sold anywhere to our knowledge.|
|ECT Solenoid (E83)||Sumitomo 6189-1092||Located on the left hand side of the transmission above the oil pan.|
|Shift Lever Position Sensor (E80)||Sumitomo 90980-12362||Located on the right side of the transmission next to the shift lever inhibitor switch.|
|MG1 & MG2 Resolver(s) (E81 & E82)||Sumitomo 6189-1240||Located on the left side of the transmission by the bell housing.|
|Oil Pump Temperature Sensor||Sumitomo 6189-0175||The connector is the small 2-pin connector in the middle of the harness between the oil pump and controller|
|HVECU -> Oil Pump Controller (A52)||Single large (7-way) connector on the side of the oil pump controller|
An open-source VCU, designed by Damien Maguire, can be purchased as both partially populated and fully populated and tested boards on his website:
The VCU is an external unit that will not fit within the GS450h inverter housing. It does not replace the GS450h inverter control board, instead it interfaces with it over USART.
For those who have purchased the fully built board, the mating connectors for the VCU are Molex parts:
- 33472-2002 (Left side, grey in colour)
- 33472-2001 (Right side, black in colour)
- 33012-2002 (Crimp terminals)
These parts are available from many electronics distributors.
V1 - This board was sold tested but also as a bare logic board requiring purchase of your own components and SMD placement and soldering skills. https://www.evbmw.com/index.php/evbmw-webshop/toyota-bare-boards/gs450h-bare-pcb
V2 - A new board source was found to be both high quality and low cost. The boards were redesigned around the inventory of parts available from this supplier. In particular the high cost of populated and soldered boards (10x the price) from the source used to make the v1 boards is so significantly lower on the v2 that there are likely no savings by building and soldering the board yourself. Software is still in development.
There are currently no vendors who offer support on any aspects of the GS450h VCU.
Community support is available on the Lexus GS450H VCU Support Thread