1. Heat (can’t really be avoided)
2. Using rapid charge
3. Keeping it above 80% charge level for prolonged periods
4. Letting it drop bellow 30% charge level
5. Natural aging of the battery

1. Use battery conservation mode if your laptop has it. Keeps the battery between 55-60% charge level
2. Use rapid charge only when necessary, not all the time by default
3. Don’t put your laptop on a stove

Every battery has an estimated number of charging cycles, which it can go through before the capacity/health falls under 80%. One cycle is 100 times charging by 1%. In essence: One cycle equals charging from 0% to 100% or charging twice from 50% to 100%.

The number of maximum cycles until reaching 80% health is different for each battery and is greatly affected by other factors, such as those described above. Generally, on average, with average usage, one can expect about 500 battery cycles before the capacity falls under 80%.

You can use a free monitoring application, such as HWiNFO, or if your laptop came with a proprietary application, check for battery information in there.

For Lenovo Legion laptops, you can use for example Lenovo Legion Toolkit and check the information in the Battery section.

Battery charging will start only when the charge level falls under preset threshold. For Lenovo Legion laptops, the battery will be allowed to drop by 5% before the charging is resumed. In normal mode, that is when battery drops to 95%, in conservation mode, this is 55% charge level. This is a smart feature implemented to prolong battery lifespan. There are two reasons why the battery level may drop even while plugged: Normal loss of charge, that can't be affected and happens in all batteries in all devices. The other reason is when a device draws from the battery even during charging. Ideally, a device will be able to draw power independently from the outlet or the battery as needed.

• Some devices, however, will be able to draw power only through the battery, either partially, or entirely. So power will go from the outlet, to the battery, and from the battery, to the device. This negatively affects battery lifespan and used to be rather common in mobile devices in the past.
• In some cases, a device will be able to draw power directly from the outlet, but only up to a certain level. If the power draw goes over this limit, the device has two options: Draw additional power needed directly from the battery, or limit the performance to keep the power draw under this limit. How the device behaves in a specific scenario depends on its configuration.
• The behaviour can be even dependent on the charger used. For example, when using USB-C charger, the performance may be limited to keep the power draw under this limit, and while using proprietary charger from the laptop manufacturer, if the laptop needs extra boost above what can be drawn from the outlet, some power may be sipped from the battery.
• To make things even more complicated, another possible option is that a laptop comes with a high wattage charger, for example 300W, and be only able to use directly 230W, with the rest reserved for charging. In this case, if the laptop needs to draw more than 230W, the extra power will be drawn through the battery, even though on paper the charger should have enough power. All of these things depend on how the manufacturers configure their devices. This solution can be tricky to spot, as depending on how big and how often the power spikes above the limit. If the spikes are infrequent and the charger is powerful, it may be hard to notice during regular use. However, on the flip side, if this does happen to your device, due to the spikes being too short to even notice, it will also likely have negligible impact on the battery health and add only a couple additional cycles per year.

Battery can not hold its charge indefinitely and will slowly lose charge over time. Additionally, if you unplug your battery while not using your laptop, there is a chance the laptop still draws some idle power. Whether because it keeps something internal on standby, or has some device connected to an always-on USB port, or it's put in a low power state instead of being fully shut down, like in sleep, etc.

— m164