Twining prius inverters. Implausible idea?

[barracuda816]

I have can't seem to get rid of the idea of running two inverters with a boost function (ie a Prius inverter) and I want to run it by the collective to see if this could even be theoretically possible to match the phases so they don't just fry each other.

The reason I would want to do this is I am looking at carrying out a conversion on a small and light car (I haven't chosen which yet but im thinking along the lines of a trabant or smart roadster) these have severe weight restrictions but don't need huge power. I don't need a massive range, around 100km would be great and wanted to use something like two 6.3kw MEB modules. Obviously the voltage would be too low to be practical for either an outlander motor, a MGR or even a Volvo ERAD. But as far as I am aware the boost function seems to be limited to 22kw? That would be less than I would like but 44KW in a small car I think would be sufficient.

So what do you guys think? a non starter or could I be on to something?

[MattsAwesomeStuff]

Well...

First up, keep in mind that you're probably not losing slow speed acceleration. Even with low voltage you'll still have some pep there.

You'll be losing your higher speed acceleration. 22kw is enough to maintain highway speed, but not enough to get to highway speed.

...

For the same cost, are you sure you don't just want to use a higher voltage battery pack?

Even a smaller high voltage battery pack? Like, the voltage of whatever you'd be boosting to, to use it kinda like a big capacitor, just for the 10-20 seconds of accelerating to highway speed?

Even something goofy like a pack of 18650s out of tool packs. A single 18650 will do 50 amps I think (for 2 minutes). 200v @ 60a = 12kw. And it'd only be an additional, like, $50-100 for the 50 cells. It wouldn't be much bigger than a box of crackers.

Or really, any actual hybrid battery. You only need 20 seconds of energy.

...

Sorry, not answering your question the way you want it answered. Go nuts if you want to parallel up two boost converters but, seems like there'd be a few different ways of hitting that goal.

[johu]

The boost converters are current limited, not power limited. The current limit seems to be around 100A. Someone burned the booster coil by sending over 100A through it for a prolonged time. So 2 MEB modules are like 90V. 90Vx100A = 9 kW or should you actually manage to parallel the converters 18 kW.

I agree with Matt, go for higher voltage and enter the large ecosystem of 400V based things being used here.

The old school way would be Curtis and the like, targeted at 70-140V.

[Aragorn]

Not better off buying a 400v hybrid pack for the same ~12kwh?

BMW/Range Rover/Volvo etc.

[barracuda816]

Thanks for the reply guys. It makes sense that the inverter is current limited not power limited. Also good to know for higher voltage systems maybe. boosting to 650v from 400v for the extra help against the back EMF? But it makes the use of a 90v system a non starter.

I don't know of any other inverters with a boost stage that have a higher current capacity, do you guys?

My initial (and more sensible plan) is a Range Rover pack at 14.7kwh. But I can't get over the more than 6kwh from one module at what, about 32kgs each? Where as a Range Rover pack is well over 100kgs maybe 150 ( I know the housing weighs a fair bit but even without that) also like the idea for the cells to be easily removable/ swappable.

Thanks for all your input, This is a great forum for being able to just talk through ideas without being slammed as an idiot.

[Aragorn]

I imagine the range rover modules will be a little heavier per kwh than the MEB ones, but its probably not that much more, and you'll end up with a much simpler result with plenty power and voltage available to run the motor without worrying about boosting.