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IUoU is an DIN-designation〔 (DIN 41773) for a lead-acid battery charging procedure that is also known as ''3-stage charging'', ''3-phase charging'', or ''3-step charging''. It consists of three phases (or stages), to be executed by a battery charger. The three phases are: ''I-phase'' (constant electric current), ''Uo-phase'' (constant over-voltage), and ''U-phase'' (constant voltage). The purpose is to fully charge the battery in a relatively short time without reducing its life span and to indefinitely keep the battery charged as long as the charger is connected. ==Stages== Stage 1 is called the ''I-phase'', ''constant-current stage'', or ''bulk charge stage''. This phase occurs when an IUoU charger is connected to a deeply discharged battery. The charger provides a constant current, typically the maximum current that the charger is capable of producing. As a result of the current, the battery absorbs the charge and its voltage rises. The charger limits the maximum voltage to ''Umax'', a constant or temperature-dependent maximum, typically around 2.4 V per cell. Once the Umax voltage is reached, typically when the battery is charged to 70–80% of its capacity,〔 the charger enters the Uo-phase. In case of a battery that is more than 80% full, this may happen immediately once the charger is switched on. Some chargers〔 may keep the voltage at ''Umax'' for some time and allow the current to drop to 80% of the constant-current value, before proceding to the next stage. Stage 2 is called the ''Uo-phase'', ''constant-voltage boost stage'', ''absorption stage'', or ''topping charge''. In this stage, the battery is continued being charged at a constant (over)voltage Uo, but the charge current is decreasing. The decrease is imposed by the battery. The voltage in the Uo-phase is too high to be applied indefinitely (hence, overvoltage), but it allows charging the battery fully in a relatively short time. The Uo-phase is concluded when the charge current goes below a threshold Imin, after which the U-phase is entered. This happens when the battery is charged to around 95% of its capacity.〔 Some manufacturers〔 follow this stage by a second constant-current stage (with a gradually increasing voltage) before continuing with the U-phase. The voltage Uo may be the same as Umax in the previous stage, or it may be taken slightly higher. Stage 3 is called the ''U-phase'' or ''float charge state'', the voltage is reduced to a value that is safe to be applied for long periods (weeks) without significantly reduce the lifetime of the battery. During this phase, the charge current decreases gradually to a small residual value that compensates for any self-discharge of the battery. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IUoU battery charging」の詳細全文を読む スポンサード リンク
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