[Feature Request]: Battery Chemistry Type Selection

[CheeseIsGood27]

Platform

NRF52, ESP32, RP2040, Linux Native, other

Description

Feature request to add a drop-down menu or way to select battery chemistry for INA219, INA260, or INA3221 sensor under the power config menu.

Lines 14-28 of power.h seem to define several battery chemistry types under the "OCV_ARRAY" variable:

#ifndef OCV_ARRAY
#ifdef CELL_TYPE_LIFEPO4
#define OCV_ARRAY 3400, 3350, 3320, 3290, 3270, 3260, 3250, 3230, 3200, 3120, 3000
#elif defined(CELL_TYPE_LEADACID)
#define OCV_ARRAY 2120, 2090, 2070, 2050, 2030, 2010, 1990, 1980, 1970, 1960, 1950
#elif defined(CELL_TYPE_ALKALINE)
#define OCV_ARRAY 1580, 1400, 1350, 1300, 1280, 1250, 1230, 1190, 1150, 1100, 1000
#elif defined(CELL_TYPE_NIMH)
#define OCV_ARRAY 1400, 1300, 1280, 1270, 1260, 1250, 1240, 1230, 1210, 1150, 1000
#elif defined(CELL_TYPE_LTO)
#define OCV_ARRAY 2700, 2560, 2540, 2520, 2500, 2460, 2420, 2400, 2380, 2320, 1500
#else // LiIon
#define OCV_ARRAY 4190, 4050, 3990, 3890, 3800, 3720, 3630, 3530, 3420, 3300, 3100
#endif
#endif

REQUEST: A drop-down menu, or even a few lines to define a custom "OCV_ARRAY" value in the power config would be very useful for alternative battery chemistries.

CONCERN: Most boards used for Meshtastic have an on-board LiPo charge circuit wired direct to an ADC pin for voltage reading. I don't think the modified "OCV_ARRAY" would cause an issue related to the ADC circuit and voltage divider, but I'm uncertain.

ISSUE THIS SOLVES: Currently, I have a single LTO cell boosted to power a Heltec V3 using an INA219 for voltage sensing. The INA219 works perfectly and replaces the ADC voltage reporting as expected (#3283 ). The problem is that when the voltage is reported back at 2.8v (full charge for an LTO) the Heltec goes to sleep because it's below the 3.2v cutoff of a standard LiPo. I cannot currently monitor my battery voltage and keep my node awake simultaneously without custom-editing the firmware or hacking the ADC voltage divider to fake the expected voltage.

[roha-github]

You can increase the ADC multiplier via the power configuration to shift the zero point from the percentage value of 3.1 volts to 2.8 volts.

I do it the other way round with my Solar Node to switch off at 3.45 volts instead of 3.10 volts. I then check every hour whether the battery is charged again (default is 24 hours with active power saving).

[CheeseIsGood27]

I don't think the ADC multiplier is tied to the output from an INAXXX device, only the ADC pin on the device used. Adjusting it had no effect.

[todd-herbert]

Just to update, I've done some work on this today, but need to wait until I'm back home next week to test it properly.

[mrjackson]

An option for custom voltages mapped to 0-100% would also be handy for the tinkerers out there.