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lithium_ion_batteries [2012/09/26 22:22] vincentpants created |
lithium_ion_batteries [2012/09/26 22:25] (current) vincentpants |
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| - | ince many people might be using with lithium batteries for the first time, I thought I would mention a few guidelines for those unfamiliar with this most excellent of energy storage media. Lithium cells are not difficult to charge correctly, but they are very particular. To paraphrase a well-known american street sign, "Differ and it will hurt". The hurting could potentially involve fire and lithium-flavoured brimstone. | + | Since many people might be using with lithium batteries for the first time, I thought I would mention a few guidelines for those unfamiliar with this most excellent of energy storage media. Lithium cells are not difficult to charge correctly, but they are very particular. To paraphrase a well-known american street sign, "Differ and it will hurt". The hurting could potentially involve fire and lithium-flavoured brimstone. |
| Charging consists of a constant-current phase, during which the voltage rises, followed by a constant voltage phase where the voltage is not allowed to exceed a certain value, while the charging current steadily declines. Commercial chargers typically set Vmax at 4.2V. By setting the voltage limit a bit lower (4.1V, say), you can be kinder to the cell and get more useful charge cycles out of it by preserving its capacity for longer. That is one advantage of setting up your own charge control circuit. The constant charging current, in milliamps, should not exceed the cell's capacity, expressed in milliamphours. Charging current (in mA) is most often in the range from 0.5C to 08.C, where C is the capacity in mAh. You will find lots of ideas for chargers online, so make sure that they conform to this pattern. One of the simplest to build consists of an LM317 configured for current limiting feeding into another LM317 configured for voltage regulation. | Charging consists of a constant-current phase, during which the voltage rises, followed by a constant voltage phase where the voltage is not allowed to exceed a certain value, while the charging current steadily declines. Commercial chargers typically set Vmax at 4.2V. By setting the voltage limit a bit lower (4.1V, say), you can be kinder to the cell and get more useful charge cycles out of it by preserving its capacity for longer. That is one advantage of setting up your own charge control circuit. The constant charging current, in milliamps, should not exceed the cell's capacity, expressed in milliamphours. Charging current (in mA) is most often in the range from 0.5C to 08.C, where C is the capacity in mAh. You will find lots of ideas for chargers online, so make sure that they conform to this pattern. One of the simplest to build consists of an LM317 configured for current limiting feeding into another LM317 configured for voltage regulation. | ||
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