Your design should control when, how quickly (i.e. with how much current), and for how long the batteries charge and discharge.
The desired function of the system during eclipse is straightforward: no power is coming in from the solar panels, so all the power flow is just from the batteries discharging into the subsystems (loads).
During sunlight, it’s a little more complicated - we need some part of the system (i.e. a battery charger I.C.) to control how much of the power coming in from the solar panels is used to charge the batteries and how much goes to the loads. Specifically, the system need to prioritize sending enough power to the loads and then any left over power can go into the batteries to charge them. Conversely, if there isn’t enough power coming in from the solar panels to power the satellite during a given sunlight period, the batteries need to discharge to assist them. All of this requires a controller whether that be an IC connected to I2C or an IC that does it in a more analog way. Additionally, we need something to track how much of the battery’s capacity has been discharged and tell the on board microcontroller because that number should always stay below 20%
A list of sequential tasks for the project. The project is complete when all tasks are complete
Space for research notes, open questions, progress logs
Battery Charger IC
Product #1: LTC4015
Product #2: BQ25856-Q1
Product #3: ISL9237
Battery Monitor IC
Product #1: BQ76905
Product #2: LTC 6804-1
Product #3: BQ29330
Product #4: BQ79616-Q1
Product #5: ADBMS6817
Product #6: MAX11068GUU/V+T
Pins: 18 (SHDN), 20 (THRM)
AEC-Q100