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Reply To: Battery Measurement accuracy

Home Forums Mayfly Data Logger Battery Measurement accuracy Reply To: Battery Measurement accuracy

#14184
neilh
Participant

Here is some new data. I had the FTDI cable connected, and seems like it was influencing things somehow. I cut the RX (always high ~ 3.5V) and that changed the way Q1 is turned on. Still not sure why.  I removed the FTDI altogether and repeated the readings.

The Mayfly will now continue operating to V_batt = 3.00V, Proc resets when I drop to 2.95V (motioning with a reasonably professional Meterman 37XR voltmeter).

The overhead/buffer difference V_batt &rail3.3V is now about 0.15V, probably mostly the SPX3819.

However it does show that the mega1284 A6 measurement is only linear to about 3.5V.

https://3qzcxr28gq9vutx8scdn91zq-wpengine.netdna-ssl.com/wp-content/uploads/V_batt-Characterization_2020-06-04-1432.jpg

The 2nd graph shows the difference between V_Batt and 3.3V rail

https://3qzcxr28gq9vutx8scdn91zq-wpengine.netdna-ssl.com/wp-content/uploads/V_batt-Characterization_2020-06-04-1434.jpg

I’ve added the .xls with the readings.