Squeezing full capacity out of 2s1p Li-Ion

General
1

I’m looking for a new FC/esc combination that ticks most of the boxes below, listed in order of importance. Please offer any knowlege or past experience doing similar.

  1. FC and esc, or AIO, needs to operate down to say 5.2v. Or, just the esc since I could use a step-up voltage board to power the FC.
  2. H743, dual IMU preferred, that operates at 5.2v, is this even possible?
  3. Min. 4k gyroscopes
  4. ESC is capable of RPM telemetry down to 5.2v, preferrably dshot without a telem wire
  5. Decent blackbox size, preferrably SD card.
  6. 25mm mounting or smaller

Awhile back I modified a Hackrc esc to operate down to 5v, but I’m looking for something more modern. Should I consider an “1-2s” F7 AIO, for just the ESC, and a Matek H742 mini. Could such a thing be wired up?

2

This is an interesting question as I also thought about such solution.
I think nearly all FC can do the job with a small modification.
All FCs work on the USB power which is around 5V.

3

Ah yes, of course, thank you. I now recall that FC specs list higher voltages because they usually have BECs > 5v.

I guess this narrows it down to finding / selecting a modern and reliable ESC that provides dshot and operates down to 5.2v.

4

You can try FETtec ESCs. They provide telemetry and AFAIK meet all your requirements

5

There are Whoop AIO boards that operate on 1S power but never saw one with an H7 or 2 IMU’s. They have BLHeli_S though so you get Dshot with Bluejay. But many are F411 based which are not supported if you wanted to give up the H7. There are a few F405 based supported boards though.

6

BLHeli_S would be acceptable, but I can not live without H743. Gemini said the following, and I’ll be researching FETTEC ESCs minimum operating voltage. It seems like they operate at a voltage lower that they need to boot and initialize.

From AI:

2. SFOC 4-in-1 ESC (50A)

  • Rated Range: 2S - 8S LiPo

    GetFPV

  • Minimum Operating Voltage: 6.0V (Nominal 2S voltage is 7.4V, but the hardware is rated down to 6.0V).

  • Note for Sensor Calibration: While the ESC can run at lower voltages, FETtec specifies that the initial power-up for sensor calibration requires a power supply of at least 10V and 10A.

7

I did not mention in my original post that I was assuming 18650 cells for a <250g build. FETTEC escs appear to only operate down to 6v. I found 18500 2mah cells from Panasonic with 7.5A continuous discharge and will be therefore moving to 3s 18500.

8

Can you share more information about these Panasonic cells. Full article name, article number, link to the datasheet or a link to your supplier

9

I have not started researching the various 18500 cells. I’m not confident about the 7.5A continuous discharge rating that I mentioned when I was looking at the Panasonic NCR18500A 2040mAh. I’ll plan to post here after doing some additional research. Basic specifications for the Panasonic cell are shown below, but I’m not sure that I trust the source. Three makes of 18500 cells are shown available here: 18500 Batteries | Lithium-Ion Rechargeable Cells

{741A327B-2128-4A43-A3C7-AD284B6441E7}
{741A327B-2128-4A43-A3C7-AD284B6441E7}921×669 70.9 KB

10

The Panasonic NCR18500A is rated as maximum continous current = 2C. This is only around 4A as also shown by your link.

11

NCR18500 are only a standard LiIon cells.
High Current cells are for example the UR18650, but the form factor and weight are bigger

12

In my own 2S adventures I found the minimum voltage to be the biggest issue with boards rated 2S and up. They are often meant for LiPo batteries so a minimum voltage of 6V or 6.5V is fine. But if you’re trying to get everything out of a LiIon then you’ll need to go less than 6V. You’ll want at least 5V (preferably less) so the quad doesn’t just descend out of the sky. In my experience the motors didn’t stop, they just didn’t have any power left, even though the battery was still good.

If you’re stuck on 2S then consider ESCs that are 1-2S rated.

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