One particularly persistent battery myth is that you need to occasionally fully discharge and recharge to erase “battery memory.” This couldn’t be more wrong for lithium-ion batteries. It’s a leftover myth from lead-acid cells, and it’s pretty undesirable to charge your modern smartphone in this way.
Partial charging is just fine for lithium-ion batteries and can have some positive benefits for cell longevity. To understand why it’s important to appreciate how a battery charges. Li-ion batteries draw constant current and operate at a lower voltage when closer to empty. This voltage gradually increases as the cell charges up, leveling off at around a 70% charge before the current begins to fall until the capacity is full.