How did the PHEV kits let you drive electric?

I know the market is almost gone for these kits, and I would also buy a Plugin Prius 3rd gen instead. But, looking at a Lexus hybrid of that time, I'm wondering what I can learn from this aftermarket PHEV era.
The Lexus is very different, but also much the same (such a seperate HV ecu and engine ECU, important for modding).

First question is, how did the PHEV kits let you drive at high speed with ICE engine off?
I see that there was a lot of StateOfCharge spoofing that could seriously help, but that will never let you drive without ICE on speeds up to 70mph, I assume.
There was another way which involved starting and stopping to switch modes and could only go up to 50mph? I understood it said the ICE was "not available" ? Not really an interesting way to me, wouldn't want to stop to switch.

Also, did it mean the Prius (without ICE) only had around 40hp or so? Or would it pull more Amps from the HV battery?
I think that would require modifying the signal between the HV computer and the electric motors (in the gearbox)

 

Thanks, so cut the fuel and reset any error codes coming up. Is it true that the out of gas mode is the one where you have to stop and flip the switch again, to continue with the ICE again? And which was also limited to 52mph or some number like that?
Or does it let you switch between these modes while driving?

Because these PISS systems together with Ewert energy systems software (?) allowed the Prius go up to 70mph without ICE.
I assume then it also turns the ICE without fuel, to not get the speed of MG1 get to high.
Is this a different solution than the out of gas mode?

The Lexus actually has a second planetary gear which makes a first and second gear, so I guess we dont know how that would work out. I think it switches above 70mph so probably not relevant.

The Lexus uses a larger battery pack, just more cells then Prius, which makes it a 288 volt pack. Conveniently close to packs of plug-in hybrids and small electric cars like i-miev.

 

Additional thoughts/questions (I can't edit post above)

So I guess the other big thing is SOC spoofing. If I understand correctly you send a message in which you say SOC is 90%, in which case the HV computer will prioritize the electric drive, because it wants to protect battery. Correct?
I guesd this plus out of gas mode can get things up to speed, but I what speed?

I guess it could work by leaving the original BMS in place. Then set up the voltage sensing per cell either with fixed voltage divider to fool it, or hook it up to individual cells of the new pack, and measure perhaps a slightly higher voltage. First one is easier.
Then, use a complete pack of a plug in hybrid or i-miev / ion / czero. Together with the BMS and charger of that car.
Then, create something that translates the SOC of the new BMS to values for the HV computer. Which is probably a high SOC all the time and then a quick drop off towards a low level when the new battery is getting close to empty.
But I guess fooling it to a high SOC will also block any regen.

Or get rid of the original BMS and do all of the messaging yourself, but that is more work.

 

Thanks for the info. I would like to work with a complete replacement of the HV battery.

The plan I had worked out is: Take a GS450h (2006 to 2010), remove the 288v HV battery and replace it with a 300V battery from Mitsubishi. This could be from a facelift I-miev or from an Outlander PHEV. You could even continue the cell sensing wiring to the Mitsubishi cells in that it would just show a slightly higher cell voltage but allow for detection of cell problems.
So keep the Lexus BMS. But also keep the Mitsubishi BMS, in fact the whole system which includes charging from the grid.
So keep the Mitsubishi system happy and use it as such, so it also does cell balancing.
Then to the SOC spoofing of course, based on SOC measured by Mitsubishi BMS.

Optionally sit between HV ecu and engine ecu to create full electric drive when you want. Lexus drivetrain is pretty powerful but car is also heavy.

However, I could not pull this of now, it would have to be later. Possibly next year.
The big thing is though, that it would still be a big car consuming lot of fuel and electricity. And a fast car which means I will use that power
The prices of new electric cars are coming down which means they are becoming more affordable in lease contracts as well. And more efficient.
I am used to small cars as daily drivers, so a small electric car would suit me fine, even with lower range. Driving a modified GS450h, would blow a lot of fuel in hybrid mode, and I am afraid would drive very annoying (slow) in electric mode. Unless you modify it to the extend where it can just make the 200hp ong battery power alone. Not impossible, but too much for me.

So currently, I am very unsure if I will ever do it. But as you can see, the idea with the Mitsubishi battery pack including everything matches quite well and means you don't have to reinvent the wheel. The main task is to do SOC spoofing. So not a project of years, because I don't like that.
Maybe I get tempted when I see a broken GS450h or RX450h one day.