openinverter forum

Hi, Im Thomas! Im studying electrical engineering as an undergrad and have been interested in the realm of diy electric mobility and energy for while. New to the forums but have been reading along, which has been getting me slowly poised up for a EV conversion. EXCITED.

Finally pulled the trigger and acquired a Gs450h inverter and tranny for the conversion i want to do. Wanting to go down route of using zombieverter VCU to control.

So I'm committed now. Started to think in more detail about options for batteries and i have this one crazy (well its crazy in my mind) idea that would make use of the boost converter in its OEM use case.

Would appreciate someone with more experience than myself pointing out the fatal flaw i have yet to see in this:
Motivation: I want a cheap-ish and powerful build. ~200kW and range isnt a huge deal maybe up to 150km or so. For the big players this prolly isnt overly impressive but for a newb like me... THATS COOL ENOUGH.

Prospected conversion vehicle is GT86 which doesnt have much space for heaps of batteries either. Originally leaning towards LFP cells for good balance but realised even if i was using power LFP cells. id need HEAPS to comfortably to 200kW at like 5C and have reasonable range. Noticing that battery hookup also lists LTO cells which turn out to comparable energy density to LFP yet WAYYYY more power. To complement its low energy density perhaps NMC can be used which would be more space efficient in my space restricted application.

The idea would then be:
1. Since the GS450h has a built-in boost converter it should be possible to essentially do a semi-active hybrid battery configuration
2. LTO is connected directly to the inverter (ie the usual Gs450h conversion topology where the DC/DC is bypassed), then the NMC pack is connected to the boost converter input.
3. Ignoring possible dodgy startup conditions, nominally the system would act just like the typical Gs450h conversion where the main pack on the inverter bus provides majority of power
4. However im using LTO so there isnt much energy in that pack. So the NMC pack is constantly feeding 30kW into the LTO pack to keep it topped up. 30kW should be plenty for cruising at any legal speeds.

I've had a quick think and im sure there are plenty of details that warrant investigation with regards to not blowing up the boost converter on initialization, since the OEM application doesnt expect a DC voltage applied to the bus. But this doesnt seem to be the death of the idea to me, appropriate logic to make sure the bus voltage is indeed higher than the boost converter input before connecting up big contactors should be the idea.

If that does sound reasonable of an idea... my question is:
Does zombieverter VCU currently have implemented the control of the DC/DC converter? In particular i imagine i'd need control over the average current/power. Would prefer to utilise the control loops implemented in the OEM logic rather than DIY it.

And since this is my first post I'd like to thank everyone for all the time, effort and intelligence that has already gone into all these projects and to building this community.

I dont know the specifics of the chemistry, or the cells your looking at, but even if LTO was able to withstand higher C rating, the fact its a fraction of the capacity surely moots that point?

For instance if you've got 2kwh of LTO and 30kwh of NMC, then even if the LTO cells can do 10x the C rating of the NMC ones, you can still get more power out of the NMC pack because of its vastly larger capacity.

Its your first build. Dont overcomplicate things. Apply the KISS principle. Use salvage Automotive batteries that are tried and tested. Buying bare cells at this point is an excercise in futility and wild overcomplication.


To answer specifically, the only systems i've seen with control over the boost converter are those with full board replacements such as the Prius Gen2/3. Zombie is talking to the original control board, and i've not seen the boost converter used, though that doesnt mean its impossible.

The boost converter cannot be used. It will limit, not increase power as all current passed through the boost inductor, whether boosted or not.
You have to connect to the inverters DC bus directly to get any meaningful power.

Same thoughts as Aragorn, just fit a powerful NMC pack. Plugin-Hybrid packs are more power and less energy dense, so may be your choice.
You're just going to pull peak power for a few seconds, don't worry too much about it unless you want to build a race track vehicle

Thanks for your inputs!! I'm talking to the legend himself.

Point taken on going the simple route for an initial attempt. I imagine with any pack built cell by cell or as oem module, a custom BMS and integration into rest of system will be necessary so the difference in difficulty appears to be in mechanical enclosure and electrical connection reliability. I would prefer to build my own pack and have the flexibility to chose.

Re limiting not increasing power. I was proposing that the LTO pack would be connected directly to the DC bus. Whilst an NMC pack could be connected to the boost converter. This way the total power output would be the LTO packs max power limited by C rate + 30kW. But more importantly so that the LTO's low energy can be complemented with something else such as NMC. I was thinking more on the order of 8kWh of LTO which would give 180kW peak power, and 18kWh of NMC which would be more comfy at 60kW max. Having no experience with this, I'm worried exceeding the recommended discharge rate will hurt battery longevity. Even at like 5C for NMC (which seems high?) I would struggle to fit 40kWh in and the complexity in splitting the cells/modules off into seperate battery boxes like what zaptero has done in his EV86 is daunting.

Regarding implementation.I wonder if Damien's reverse engineering process is documented. I imagine a similar sort of sync serial communcation is used to tell the OEM logic board how hard to drive the DC/DC converter, which i could try to figure out.

Hi, this may give some insight
operating a factory Gs450h, with 98 Lipo4, switched parallel to the Nimh 288v, judicially when voltages are acceptably matched.
The Boost converter limits the available power to 37kw.
This is a bit low for some driving circumstances , maybe 5%. . Stratagem was to avoid percieved problems like steep hill starts, etc.
Have operated in this mode for many months as a test program, when gathering some idea if how it all works, and it worked well for me. Have some ideas to increase the usability, on the project list..much to learn..
For simplicity follow the advice above.

Is there a thread where you have documented more about your project in detail? Would love to look into it more.

Not at this stage, happened ahead of finding this O inv platform, however aiming to revisit the project, and start a thread. So sorry this has been to one side whilst learning and exploring hybrid options in a Bedford van, and gs300h L210 transmission focus. Wip

Woodfie wrote: ↑Thu Jun 13, 2024 3:34 pm Not at this stage, happened ahead of finding this O inv platform, however aiming to revisit the project, and start a thread. So sorry this has been to one side whilst learning and exploring hybrid options in a Bedford van, and gs300h L210 transmission focus. Wip

Thats awesome, would be eager to see it when you do get time to share.

Woodfie wrote: ↑Thu Jun 13, 2024 3:50 am Hi, this may give some insight
operating a factory Gs450h, with 98 Lipo4, switched parallel to the Nimh 288v, judicially when voltages are acceptably matched.
The Boost converter limits the available power to 37kw.

Sorry, i don't mean to hijack but I think it will tie back in..

So you're getting 128 amps through the boost converter?

Any idea if it's the same inductor and igbt module as a gen 2 Prius?

I've only seen estimates of power through it so far.
I went a bit off the deep end reconfiguring the gen 2 Prius DC-DC for a project I'm working on. I'll share code & the project when it's tested, done, and working.

Aragorn wrote: ↑Wed Jun 12, 2024 8:46 am For instance if you've got 2kwh of LTO and 30kwh of NMC, then even if the LTO cells can do 10x the C rating of the NMC ones, you can still get more power out of the NMC pack because of its vastly larger capacity.

Coming back to this thread to see If i can dissuade myself before i start to build the hardware.
This is a good point but I think the key is that LTO isnt 10x less energy dense. Its probably closer to 70Wh/kg vs 350Wh/kg best case for both. So its 5x difference.
c-rate is probably close to 5x in the other direction so it almost cancels out.

Then LTO has other desirables inherent to the chemistry like cycle life, safety and wide temp range.

I've found a really cheap source of LTO so it makes sense all other things considered.

But It looks like LTO is not the future for production vehicles who's chassis are built to fit an order of magnitude more energy than what im thinking. The other chemistries would be good when ur pack is 50kWh in the first place or something. So this might be a very niche choice that not many others would find justifiable as modules/cells of those other chemistries get more ubiquitous. At the moment in Australia, none of them are that common so its less of a consideration.

jrbe wrote: ↑Mon Jan 06, 2025 3:51 am
So you're getting 128 amps through the boost converter?

Any idea if it's the same inductor and igbt module as a gen 2 Prius?

Yes, think saw 125 A drawn on . Fitted with service/repair folks information that the Lexus was harder on the same slices as used in the Prius, around 100A.

Havent yet looked at the gs450h inductor

Gen2 nhw20 inductor is a stand alone bolt in component.

But maybe of interest, a zvw35, 2012 phev, with coil cast in the heatsinks , has the same appearance inductor..as zvw30 with a temperature sensor. The sensor is not seen on the zvw30 .
Torque pro showed 250A @ 200v from Lithium pack.
IGBT is different,