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As I was trying to understand how BeagleBone Blue is handling battery management, I encountered a battery protection IC (S-8261).

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  • How does S8261 prevents overcharging and overdischarge? (ELI5)
  • BQ29209 and MP2615 also have overcharge and discharge protection, why would you need an aditional IC (S8261)?

Bonus Question

Battery out (V_BATT) is directly connected to motor drivers (TB6612FNG).

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  • What's point of feeding the dc motors with a non-constant voltage(V_BATT)?

Source: https://github.com/beagleboard/beaglebone-blue

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It looks like all three ICs complement each other. The MP2615 is CC-CV charger with overCHARGE limit at 10% of CC. The BQ29209 provides cell balancing and secondary overVOLTAGE protection. The S-8261 provides current limit during discharge, and overDISCHARGE protection, and the secondary overcharge (voltage cut-off at diminishing current) comes as a bonus.

What's the point of driving the motor directly from VBAT? Likely a better overall efficiency, to avoid losses in DC-DC conversion.

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  • \$\begingroup\$ Just to be sure; BQ29209 does not have an underVOLTAGE protection, only overVOLTAGE? (Also did not encounter anything about underVoltage in the datasheet) \$\endgroup\$
    – pmundt
    May 26, 2018 at 0:33
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    \$\begingroup\$ @pmundt, the BQ29209 is a balancer during CHARGE. The "underVOLTAGE" is a concept from a DISCHARGING process, and the BQ29209 doesn't seem to provide any function of discharge control at all. \$\endgroup\$ May 26, 2018 at 0:45

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