what kind of values does the AT%XVBAT AT command return on the Thingy91

[AndrewR]

I am trying to get battery % from the thingy91. I have the AT command AT%XVBAT running successfully. It returns what I assume is millivolts. However these value are higher than what I would expect. I have seen values of 4223, 4430, 4438, 4434, 4465. I am under the impression that a LiPo battery like the 1 connected to the thingy91 maxes out at 4.2 volts or 4200 millivolts. I have run the app for a while to drain the battery but I still continue to get the same high numbers. Am I misinterpretation what is being returned? Does anyone know how to read these values?

Also I found a LiPo voltage to charge % relationship chart for a baseline of what I expected

Capacity %	voltage
100	4.2
95	4.15
90	4.11
85	4.08
80	4.02
75	3.98
70	3.95
65	3.91
60	3.87
55	3.85
50	3.84
45	3.82
40	3.8
35	3.79
30	3.77
25	3.75
20	3.73
15	3.71
10	3.69
5	3.61
0	3.27

[Håkon Alseth]

Hi,

 

The Vsys voltage net (from ADP5360) will power the nrf9160 on thingy:91, and it will be ranging from VBATT up to 4.4V, depending on what the voltage source is. Note that this voltage is not always equal to the battery voltage.

When USB is connected, the Vsys net is up to 4.4V (4.2 + 0.2V, per the datasheet of ADP5360: https://www.analog.com/media/en/technical-documentation/data-sheets/ADP5360.pdf), but this will not be directly connected to the battery, as LiPo cells cannot (and shall not) be charged with such a high voltage.

To check the battery voltage (or charging status), you should communicate with the ADP5360 directly over I2C: https://github.com/NordicPlayground/fw-nrfconnect-nrf/tree/master/drivers/adp536x

 

When issuing %XVBAT, and USB is connected, the voltage will normally be up to 4.4V, and there is a bit of inaccuracy in the adc itself, so expect a bit of error there as well.

 

Kind regards,

Håkon

[AndrewR]

yea good call. I had to send the voltage output via LTE but once I got that working the values were all coming back sub 4200 which is what I expected the values to be. The accuracy variation inst really a problem. Just a general fuel gauge works and this gets it done. Thank you so much.