A Lithium Ion cell is fully charged when the current drops to a set level. In lieu of trickle charge, some chargers apply a topping charge when the voltage drops.

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The advised charge rate of any Lithium Polymer cell is between 0.5C and 1C; we recommend charging at 0.8C or less to prolong battery life; however, some cells can take a higher charge C-rate however the battery life will be reduced and you assume all risks and associated damages.

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Increasing the charge current does not hasten the full-charge state by much. Although the battery reaches the voltage peak quicker, the saturation charge will take longer accordingly. With higher current, Stage 1 is shorter but the saturation during Stage 2 will take longer. A high current charge will, however, quickly fill the battery to about 70 percent.

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Some Lithium Polymer Battery packs may experience a temperature rise of about 5ºC (9ºF) when reaching full charge. This could be due to the protection circuit and/or elevated internal resistance, the dynamic IR of all LiPo batteries increase along with the SOC. Discontinue using the battery or charger if the temperature rises more than 10ºC (18ºF) under moderate charging speeds.

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Full charge occurs when the battery reaches the voltage threshold and the current drops to 3 percent of the rated current. A battery is also considered fully charged if the current levels off and cannot go down further. Elevated self-discharge might be the cause of this condition.

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Lithium Polymer Batteries do not need to be fully charged as is the case with lead acid, nor is it desirable to do so. In fact, it is better not to fully charge because a high voltage stresses the battery. Choosing a lower voltage threshold or eliminating the saturation charge altogether, prolongs battery life but this reduces the runtime. Some RC chargers are designed to go for maximum capacity and cannot be adjusted; extended service life is perceived less important.