ArduCopter 5" Long-Range Standard Build

Arducopter has no way (and no hardware to do that on the FC) to measure the internal resistance of a battery without the balance leads being connected to the FC somehow.
I doubt this is the explanation.

It measures voltage and current and estimates internal resistance. It will not measure it, and will not estimate a per cell internal resistance, i never said that it did.

If the voltage drop is too big it will complain, and if the failsafes are not correctly configured it will complain as well.

How good is the battery? Did you do the initial tuning instructions?

I found the issue. It is indeed an issue of arducopter for this particular Kakute H7 mini board : current is measures by the ESC and transmitted to the FC via ESC telemetry. However for some reason, Arducopter does not extract the current measurement data from the ESC telemetry (which is sent on serial 7). There is also a “Current pin” on the FC which is one of the pins from ESC input connector. It does not read that current input either.
So I guess the ardcopter firmware and/or hwdef file for this board should be modified to be able to read from either the esc telemetry and/or from the current input pin on the fc.

Not all ESC’s provide current via telemetry. Very few 4in1’s do if you are using one of those. There is typically no problem measuring current via the current out pin of the ESC to the Current pin of the FC. Which ESC is it?

The only way you will get current via telemetry on a 4in1 ESC is if it looks something like this:
Note the 4 shunt resistors, one for each ESC section. These do not have an analog current pin, telemetry is the only source.

The FC and 4 in 1 ESC I’m using are the Kakute H7 mini and Tekko32 F4 4in1 mini 45A ESC:

This ESC measures current and sends it to the yellow current pin on the FC. That PIN is probably not defined in the hwdef.dat for this board ?

No current via telemetry with that 4in1.

Sure it is. Noted in the Readme and in the hwdef.dat
K H7 Mini

The current monitor needs to be configured as esc telemetry current monitor.

that did solve the bad battery message, thanks.
So the UART1 (rx) from the ESC telemetry is not supported and only the voltage and current pins are supported.
The PIN definition is not clear at all in the documentation , as the only line found in the hwdef.dat file with keyword “current” says : PC1 BATT_CURRENT_SENS ADC1 SCALE(1)
hard to deduce this corresponds to PIN 11?
Also the wiki says that pin 11 is for “esternal” sensors, while in this case this is an internal sensor of the H7 mini stack. I never thought the 4-in-1 ESC of the stack (sold as one product) is an “external sensor”.
Maybe we should say in the wiki that the Kakute 4-in-1 ESC from the H7 stack is to be configured on pîn 11 and that ESC telemetry does not work (that is said nowhere).

Please do a pull request on ardupilot wiki to improve the documentation

Pull request is done.thanks

Yea it is. Page down to ESC Telemetry.
ESC Telem

This was updated several months ago for the same reason you are pointing out.

That won’t work with most 4in1’s. I have an exception with an Ori32 but these are more expensive to produce, larger and heavier. Nice though.

I’m lost now concerning ESC telemetry from 4-in-1 ESCs : does it work or not ? The link to the wiki page you mentioned says y it works and explicitly mentions H7 mini as a supported board. But it does not work (ESC telemetry) in my current experience with a H7 mini and its 4-in-1 Tekko ESC (using Dshot 600).
I probably do not know some other information to take into account for it to work ?

Sure it works but they don’t often have current data. As I said there are very few 4in1 ESC’s that have a current shunt resister for each of the 4 sections. Much more common is 1 (or 2 in series/parallel) shunt resister for total current. This signal is supplied on the analog current out pin of the ESC. And so unless it does have individual current shunts then no current is present in the ESC telemetry data. Your only choice is total current on the analog pin of the ESC.

Note: I have a the same FC in a 4" quad and ESC Telemetry works fine. In my case current is available via telemetry for the reason I gave above showing the photo of an ESC that does that. Your Tekko will supply telemetry just no current thru it.

Not so. Here it is:

It works. I have this stack and it works fine (just not current - you have to get that via the individual current wire).

I get indeed individual ESC voltage measurement. But hwo to get the global average of these four individual voltages ? (batt voltage 2 is always zero in mission planner)

Is BATT2_MONITOR set for ESC (9) ?

Example. In my case BATT 1 (0 in the log) is from ESC Telemetry and BATT 2 (1 in the log) is from the Flight Controller. You would configure them the opposite.

I’m pretty sure the default setup simply reads the voltage from VBAT without needing to interpret the ESC telemetry stream - I get a correct voltage measurement without setting my sensor to ESC telemetry.

Ok ESC telemetry provides a global battery voltage monitoring but to avoid it displaying zero, the batt2_options parameter needs to be set (in addition to selecting the ESC type for batt monitor2):

I have added a final video and updated the tuned settings to reflect where I got to. I’m very pleased with this build - it works really well.