diff options
Diffstat (limited to 'include/linux/power_supply.h')
| -rw-r--r-- | include/linux/power_supply.h | 48 |
1 files changed, 42 insertions, 6 deletions
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h index cb380c1d9459..aa2c4a7c4826 100644 --- a/include/linux/power_supply.h +++ b/include/linux/power_supply.h @@ -374,9 +374,37 @@ struct power_supply_vbat_ri_table { * These timers should be chosen to align with the typical discharge curve * for the battery. * - * When the main CC/CV charging is complete the battery can optionally be - * maintenance charged at the voltages from this table: a table of settings is - * traversed using a slightly lower current and voltage than what is used for + * Ordinary CC/CV charging will stop charging when the charge current goes + * below charge_term_current_ua, and then restart it (if the device is still + * plugged into the charger) at charge_restart_voltage_uv. This happens in most + * consumer products because the power usage while connected to a charger is + * not zero, and devices are not manufactured to draw power directly from the + * charger: instead they will at all times dissipate the battery a little, like + * the power used in standby mode. This will over time give a charge graph + * such as this: + * + * Energy + * ^ ... ... ... ... ... ... ... + * | . . . . . . . . . . . . . + * | .. . .. . .. . .. . .. . .. . .. + * |. .. .. .. .. .. .. + * +-------------------------------------------------------------------> t + * + * Practically this means that the Li-ions are wandering back and forth in the + * battery and this causes degeneration of the battery anode and cathode. + * To prolong the life of the battery, maintenance charging is applied after + * reaching charge_term_current_ua to hold up the charge in the battery while + * consuming power, thus lowering the wear on the battery: + * + * Energy + * ^ ....................................... + * | . ...................... + * | .. + * |. + * +-------------------------------------------------------------------> t + * + * Maintenance charging uses the voltages from this table: a table of settings + * is traversed using a slightly lower current and voltage than what is used for * CC/CV charging. The maintenance charging will for safety reasons not go on * indefinately: we lower the current and voltage with successive maintenance * settings, then disable charging completely after we reach the last one, @@ -385,14 +413,22 @@ struct power_supply_vbat_ri_table { * ordinary CC/CV charging from there. * * As an example, a Samsung EB425161LA Lithium-Ion battery is CC/CV charged - * at 900mA to 4340mV, then maintenance charged at 600mA and 4150mV for - * 60 hours, then maintenance charged at 600mA and 4100mV for 200 hours. + * at 900mA to 4340mV, then maintenance charged at 600mA and 4150mV for up to + * 60 hours, then maintenance charged at 600mA and 4100mV for up to 200 hours. * After this the charge cycle is restarted waiting for * charge_restart_voltage_uv. * * For most mobile electronics this type of maintenance charging is enough for * the user to disconnect the device and make use of it before both maintenance - * charging cycles are complete. + * charging cycles are complete, if the current and voltage has been chosen + * appropriately. These need to be determined from battery discharge curves + * and expected standby current. + * + * If the voltage anyway drops to charge_restart_voltage_uv during maintenance + * charging, ordinary CC/CV charging is restarted. This can happen if the + * device is e.g. actively used during charging, so more current is drawn than + * the expected stand-by current. Also overvoltage protection will be applied + * as usual. */ struct power_supply_maintenance_charge_table { int charge_current_max_ua; |