Modern devices have changed the rules of charging, but many long-standing beliefs about batteries have not. That gap keeps a few outdated habits alive, even though lithium-ion batteries in phones, laptops, wearables, and electric vehicles no longer behave like the nickel-cadmium cells people once knew.
One of the most persistent problems is that these habits sound sensible. In practice, some of them can add heat, stress, and unnecessary wear, especially when they are applied to current devices that use different battery chemistry.
Why old charging habits still linger
A lot of battery advice that people still repeat today came from the era of nickel-cadmium batteries. Those older cells were affected by memory effect, so repeated partial charging could make capacity seem to shrink over time.
Lithium-ion batteries do not work the same way. Because of that difference, many of the rules that were once useful are no longer required for modern devices.
Charging to 100% is not automatically the problem
Many users still assume that taking a battery to 100% is harmful by itself. On lithium-ion batteries, that is not the main issue.
The real concern is leaving a phone plugged in after it has already reached full charge. In that situation, the device can enter trickle charge behavior, where it uses a little power and then tops up again, creating extra heat and battery stress.
That is why charging limits have become more common. Some devices now let users cap charging at around 80%, while iPhone uses optimized charging to delay the final 20% until closer to the time the user is likely to wake up.
Letting the battery drain fully is not better
Another old rule says a battery should be allowed to run all the way down before it is charged again. That idea also comes from the Ni-Cd era, when full discharge and full recharge were used to avoid memory effect.
Lithium-ion batteries benefit from a different pattern. Their wear is tied in part to charge cycle use, and each cycle is counted as capacity is used and refilled.
Charging from 20% to 80% can use fewer cycles than repeatedly going from 0% to 100%. That means partial top-ups may help batteries last longer in everyday use.
European Product Registry for Energy Labeling lists the Galaxy S25 Ultra at around 2,000 charge cycles. That figure does not mean the battery stops working after that point, but that capacity is expected to fall to around 80%.
The charger matters, but it does not have to be the official one
Device makers often recommend official chargers because they are built to match the device’s power specifications. A charger that sends too much voltage to a battery that cannot handle it can cause internal damage.
For that reason, official chargers are generally the safer choice. Still, third-party chargers are not automatically out of bounds.
The key is compatibility. The voltage and fast-charging protocol must match the device, or charging may become slower because the charger and device are not communicating properly during power transfer. When the specifications line up, charging can remain both safe and efficient without relying only on official accessories.
A newer battery requires newer habits
These myths survive because they were once tied to real battery behavior. The problem is that they are often applied to lithium-ion devices that follow different rules.
That is why charging habits now matter as much as charging equipment. Small changes, such as avoiding unnecessary full-time connection to a charger and using the right charging profile, can help reduce wear over time.
