Lexus 12v DCDC converter

[drprox]

Hi,
Has anyone used the 12v DCDC from a GS450h?

Stepping down a high voltage to 12v with the main DCDC is too much, but I think stepping down to ~250v and using this second DCDC to drop down to 12v could work.

I have the wiring diagram for it but no car - so I do not know what signals it needs to turn on.

Pics attached.

[NiHaoMike]

It would be easier to repurpose a server power supply. Most of those will work on 150-390V DC as-is.

[AdrianB]

There must be a good reason why folks aren't using these in their conversions but they seem quite easy to set up - although I could well have missed something obvious. I've just got mine up and running on the bench. It works independently of the inverter with only four wires to connect:

• HV+

• HV-

• Chassis ground

• 12v+

The converter is rated at 288vDC, which matches the Lexus HV battery pack. It wouldn't do anything at 130vDC so I stepped up my temporary pack to 170vDC and it started outputting about 13.8v. I expect it'll work properly at anything between 260vDC and 340vDC but I havent tested it yet. Of course that could still be a bit low for some conversions but possibly a useful component during testing.

There are 5 control wires on plug A but only pin 1, the black wire, is needed. Just supply it with 12v+. There's some info on the forum and on the wiki about the Yaris and Prius DC-DC converters and the wiring is very similar. The main difference is that on the Lexus the precharge wiring goes through the DC-DC converter - I can't understand how that works but it can be ignored as the converter works without it. Pin 5, the pink wire, connects to the BMS but again the converter works with this disconnected. Here's how I think the wiring connects - but I haven't fully tested it.

And if you've nothing better to do you can watch it working on YouTube.