The BQ25504 have the ability to provide undervoltage and overvoltage charging regulation, which ensures that the storage component doesn't get damaged. For programming this threshold certain resistor values are required. There's a formula on the datasheet, but Texas Instruments have a spreadsheet which calculates it.

The sum of the resistor divider should be equal to 10Mohms and the undervoltage calculation is the next following;

VBAT_UV = 1.25V(VBIAS) * (1 + RUV2/RUV1)

so, with RUV1 = 3.74MOhm and RUV2 = 6.19MOh, we get: 3.32V

The overvoltage calculation is the next following;

VBAT_OV = 3/2 * 1.25V(VBIAS) * (1 + ROV2/ROV1)

so, with ROV1 = 3.65MOhm and ROV2 = 6.49MOh, we get: 5.21V

We have to take into account too the hysteresis values, which are:

VBAT_UV_HYST = 80mV

VBAT_OV_HYST = 35mV

The IC also provides two more resistor dividers, the VBAT_OK, which turn on a flag when the battery voltage is on certain threshold and the MPPT. I'm going to try to avoid using both, for having more space and making the pcb traces simpler. The battery voltage can be monitored with an external uC, so the VBAT_OK flag is not required. The MPPT provides a more optimal energy harvesting, but for testing purposes I'm going to disable it, and if I see that makes a different, try to implement it.