Can you think of an ingenious topology to make a bidirectional converter that can make a single large cell Lithium battery supply a 48V electric scooter drive?

I don't like it when people tell me, it can not be done, or that it's not practical or something like this.

I have a 500Ah iron phosphate cell and i want to make it work on my electric scooter. The drive works on 48V. I want to make a converter that would let me use this single cell as the whole battery of the scooter. I know, this is a bit unorthodox but something in this idea excites me, so it has do be done!

How would you build such a thing? It would also have to support electric braking, so it would need to be bidirectional and i was thinking that it can function as the charger for the scooter battery anyway as it would mean that it could be configured to use any normal DC supply for charging, from a normal 48V power supply to car batteries and laptop power supplies.

I was thinking about a crazy interleaved but in principle simple synchronous boost/buck converter with like 40 channels where the channels would only need to carry under 40W each as the normal total is under 1600W while driving 45kmh and about double of that for short accelerations. I was thinking on making it on a FPGA.

But is there a more sensible solution you can think of. A 2 stage solution comes to mind, but i 'm worried about efficiency :)

the boost ratio is too high for a single-stage converter so your efficiency suffer. Otherwise you would need transformer which adds cost and reduces efficiency.

What is the lowest voltage you would want to run from?

Yes, i have thought of making the boost with an autotransformer setup. I can ask my Chinese magnetics manufacturer to make those. They have not complained too much about my small orders in the past.

But the battery has a 2,5V min voltage. And a 3C continuous current rating, so 1500A, I have not been able to test such load conditions on a single cell, but in a pack similar load conditions are common an the scooters.

If you try to run a boost for too much step up, it can get into a latch condition where it just wants to switch all the time. Don't be afraid of two-stage processing, this can often be the most efficient. It is used all over the industry for high-efficiency solutions.

2.5 V minimum voltage, but I assume that's static.

What is the internal impedance? with 1500 A draw, 1 milliohm will cost you another 1.5 V.

2,5V is the cutoff voltage. Its a LiFePO4 cell and accordion to the manufacturer, the cell voltage hovers around 3V for most of the charge for loads under 3C, falling of at the end. The manufacturer gives a pulse discharge rate of 5C under 5 seconds and the internal resistance is simply given as <1mohm :)

Putting an ultracapacitor in parallel with the battery would lower its dynamic internal impedance during transients, and can supply transient peak power demands during acceleration and regenerative braking better than the battery alone I think.

But then, the maximum voltage of the ultracaps are 2.7V.