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For example, consider a battery with a capacity of 200 Ah at the C 20 rate (C 20 means the 20-hour rate – i.e. the rate that will fully discharge the battery in 20 hours – which in this case is 10 A). If this battery is discharged at 10 A, it will last 20 hours, giving the rated capacity of 200 Ah.
Self-discharge is a phenomenon in batteries. Self-discharge decreases the shelf life of batteries and causes them to have less than a full charge when actually put to use. [1] How fast self-discharge in a battery occurs is dependent on the type of battery, state of charge, charging current, ambient temperature and other factors. [2]
For example, for a battery with a capacity of 500 mAh, a discharge rate of 5000 mA (i.e., 5 A) corresponds to a C-rate of 10C, meaning that such a current can discharge 10 such batteries in one hour. Likewise, for the same battery a charge current of 250 mA corresponds to a C-rate of C/2, meaning that this current will increase the state of ...
Trickle charging is the process of charging a fully charged battery at a rate equal to its self-discharge rate, enabling the battery to remain at its fully charged level. This state occurs almost exclusively when the battery is not loaded, as trickle charging will not keep a battery charged if current is being drawn by a load.
The empirical relationship between discharge rate and capacity is known as Peukert's law. When a battery is charged or discharged, only the reacting chemicals, which are at the interface between the electrodes and the electrolyte, are initially affected.
The fraction of the stored charge that a battery can deliver depends on multiple factors, including battery chemistry, the rate at which the charge is delivered (current), the required terminal voltage, the storage period, ambient temperature and other factors. [49] The higher the discharge rate, the lower the capacity. [50]
By 2007, monthly self-discharge rate was estimated at 2% to 3%, and 2 [6] –3% by 2016. [68] By comparison, the self-discharge rate for NiMH batteries dropped, as of 2017, from up to 30% per month for previously common cells [69] to about 0.08–0.33% per month for low self-discharge NiMH batteries, and is about 10% per month in NiCd batteries.
Useful discharge capacity is a decreasing function of the discharge rate, but up to a rate of around 1×C (full discharge in 1 hour), it does not differ significantly from the nominal capacity. [26] NiMH batteries nominally operate at 1.2 V per cell, somewhat lower than conventional 1.5 V cells, but can operate many devices designed for that ...