WILL CHARGING WITH A PORTABLE POWER BANK DAMAGE CELLPHONE’S BATTERY LIFE?

The actual phone charger is in your phone. It doesn’t matter where the power comes from, charging is always the same.

Modern Lithium Ion and Lithium Poly cells do benefit from being “topped off”. There is no lifetime penalty for charging before they’re depleted. In fact, letting a battery get too low will reduce its lifetime. You count on the phone’s software to prevent the most extreme form of this, but it’s far better to charge before the battery dies.

A typical Lithium battery will have between 300 and 500 full charge cycles. So if you let your phone die every day, you could need a new battery in less than a year. Most people don’t do that, and so it’s more common to get two or so years out of that cell.

Hybrid ccars don’t have dramatically different batteries, but they only run through a fraction if the battery’s capacity. If you had a charger that would only charge to about 80% of the battery’s capacity, and the phone cut off at 20% or so, the battery might last a decade (assuming that power cycling is the only aging mechanism… sone Lithium chemistries don’t last more than 3-5 years even without any use). Of course, you’d hate the battery life, and the phone makers would eliminate one reason people upgrade to new phones, so this is unlikely to happen.