Fast charging has gone from a premium feature to a standard one in just a few years. Modern phones can charge from 0 to 50% in under 20 minutes. But with that convenience comes a question we hear constantly at our shop: is fast charging slowly killing my battery?
The answer isn't black and white — so let's break it down properly.
How Fast Charging Actually Works
All phone batteries are lithium-ion. They charge in two phases: a fast "constant current" phase where power is pushed in quickly, and a slower "constant voltage" phase in the last 20% or so where the charger tapers down to avoid overloading the cells.
Fast charging works by increasing the wattage (power) delivered during that first phase. A standard 5W charger might take 2+ hours for a full charge. A 45W fast charger can do it in under an hour.
The trade-off is heat. Higher wattage means more heat generated in the battery cells — and heat is the number one enemy of lithium-ion batteries. This is why fast charging has a real, measurable effect on long-term battery health.
Myths vs. Facts
Best Charging Habits for a Longer Battery Life
Should You Use Fast Charging or Not?
Use it when you need it — that's what it's there for. If you're rushing out the door and need a quick top-up, absolutely use fast charging. The battery degradation over a year of occasional fast charging is marginal.
Where it becomes a problem is if you're always fast charging, in hot environments, while using the phone heavily at the same time. That combination generates a lot of sustained heat and will noticeably accelerate battery ageing.
Our practical recommendation: use fast charging for quick top-ups when you're in a hurry. Use a slower charger (or wireless) for overnight charging when you have time. And enable your phone's built-in battery health features — they're smarter than they get credit for.
💡 iPhone tip: Settings → Battery → Battery Health & Charging → toggle on "Optimised Battery Charging." This feature learns your daily routine and holds the charge at 80% until just before you typically wake up, significantly reducing long-term degradation.
When to Get Your Battery Replaced
Regardless of your charging habits, all batteries degrade over time. If your iPhone's battery health has dropped below 80%, or your Android phone is struggling to make it through the day, a battery replacement will restore performance to like-new levels.
At Empire Wireless Mobile we replace batteries starting at $49, using genuine OEM parts, in about 30 minutes. It's one of the best value repairs you can do on a phone you otherwise love.
Battery Not Lasting Like It Used To?
A battery replacement takes 30 minutes and can make your phone feel brand new. Walk in or book online — no appointment needed.
The Bottom Line
Fast charging does have a small effect on long-term battery health — but it's not the disaster some articles make it out to be. Use it when you need it, be mindful of heat, and adopt the 20–80% charging habit if you want to squeeze maximum longevity out of your battery.
And when your battery eventually does need replacing — which it will, regardless of your charging habits — come see us at 876 Danforth Ave, Toronto. Monday to Friday 12–7pm, Saturday 12–5pm.