Both iPhone and Galaxy phones can be set to stop charging at 80%. That makes them look like the same feature, but side by side the manufacturers' own guides differ on when charging resumes after it stops, whether the phone occasionally fills to 100%, and when the automatic mode turns on. This comparison uses only the two companies' official guidance.
The limits you can choose
According to Apple's guide to Charge Limit and Optimized Battery Charging on iPhone (Korean), iPhone 15 models and later let you choose a charge limit between 80% and 100% in 5% steps under Settings → Battery → Charging. iPhone 14 models and earlier have no limit option, only a switch to turn Optimized Battery Charging on or off.
Samsung's Galaxy battery protection tips describe three modes under Settings → Battery → Battery protection. "Maximum" charges only up to the limit you pick from 80/85/90/95%, and choosing that limit is available from One UI 7.0. The default "Basic" mode stops at 100% and resumes charging when the level reaches 95%. "Battery protection during sleep" stops at 80% while you sleep and fills to 100% just before you wake up.
Three differences at an 80% setting
| Item | iPhone 15 and later (Charge Limit 80%) | Galaxy with One UI 7.0 and later ("Maximum" 80%) |
|---|---|---|
| Charging resumes | After a drop of more than 5% | After a drop of about 2% from the limit (78%) |
| Charging to 100% | Occasionally charges to 100% to keep charge estimates accurate | Not mentioned |
| Learning-based automatic mode | Optimized Battery Charging: only at a 100% limit, 14 days of learning | Battery protection during sleep: about 2 weeks of learning |
First, the recharge window. Apple's English support article says, "If the battery charge level drops more than 5 percent while connected to power, charging will resume." Samsung resumes charging when the level "drops about 2% from the selected limit," and its FAQ gives the example of charging restarting at 78% when 80% is selected. Neither stops at exactly the chosen number. Apple says it charges to "within a few percentage points" of the limit, and Samsung says it is not an error if the phone sits at 79% with an 80% setting.
Second, charging to 100%. Apple states, "If you have Charge Limit set to less than 100 percent, your iPhone will occasionally charge to 100 percent to maintain accurate battery state-of-charge estimates." Seeing 100% occasionally with an 80% limit is documented behavior. Samsung's guide does not say that Maximum mode periodically charges to 100%. That is an absence of explanation, not confirmation that the behavior never happens.
Third, the conditions for the automatic mode. On iPhone, Optimized Battery Charging is available only when the charge limit is 100%, and it delays charging past 80% when the phone predicts it will stay on the charger for a long time. Apple says the feature needs at least 14 days to learn your charging habits and at least 9 charges of 5 hours or more in a given location before it engages. Galaxy's battery protection during sleep generally takes about two weeks to learn sleep patterns, requires consent to customization services and related permissions, and may not work if your sleep pattern is irregular.
Neither company says how much longer the battery lasts
Both explain the direction of the effect. Apple says Optimized Battery Charging reduces battery wear by "reducing the time your iPhone spends fully charged," and that a battery's chemical age results from a combination of factors including temperature history and charging pattern. Samsung writes that the lower the charge limit, the more it helps manage battery lifespan. But neither guide gives a figure for how many percent or years an 80% limit adds to battery life. The effect of the limit alone cannot be calculated from these documents.
An 80% limit reduces how much you can use on one charge. If that does not last the day, both phones let you raise the limit to 85% or 90%. Samsung adds that figures can vary with the device, software version, charger, and usage environment. Menu names and behavior can differ by version, so check against the settings screen on your own phone.