Ask five people whether you should charge your phone overnight and you will get five confident, contradictory answers. The honest version is more boring than either camp wants: your phone will not explode, it will not overcharge, and it also is not doing your battery any favours. What matters is not the plug — it is how long the cell sits at full charge and how warm it gets while it does.

What happens when you charge your phone overnight

Every phone made in the last fifteen years has a charge controller that stops drawing current at 100%. There is no overcharging in the old NiCd sense. Once full, the phone runs off the wall and occasionally tops up the few percent that leak away.

The problem is chemical, not electrical. Lithium-ion cells age faster at a high state of charge, and faster still when warm. A battery held at 100% for eight hours every night ages measurably quicker than one that spends the night around 60%. Manufacturer testing generally puts a modern cell at roughly 80% of original capacity after 500 full cycles — but that figure assumes moderate conditions, and constant full-charge heat drags it down.

The 20-80 rule, and why it is not fussy advice

Keeping a battery roughly between 20% and 80% meaningfully reduces stress on the cell. The voltage at the top and bottom of the range is where degradation accelerates. You do not need to be religious about it — the occasional full charge before a long trip is fine — but if your daily pattern is 100% overnight, 100% again at your desk, you are paying for it in a year.

Both major platforms now automate this:

• iPhone: Settings > Battery > Charging. Optimised Battery Charging learns your alarm and holds at 80% until shortly before you wake. Newer models add a hard 80% limit you can set manually.
• Android: varies by maker. Samsung has "Protect battery" under Settings > Battery > Charging. Pixel has Adaptive Charging. OnePlus calls it Optimised Charging.

Turn it on once and stop thinking about it. That single toggle resolves most of the debate.

Heat is the real villain

Temperature does more damage than charge level. Sustained heat above 35°C accelerates capacity loss substantially, which is why the two genuinely bad overnight habits are charging under a pillow or duvet, and charging inside a thick case on a warm surface.

Take the case off if your phone runs hot while charging. Put it on a hard surface, not fabric. Skip fast charging overnight — you have eight hours, so there is no reason to push 65W and the heat that comes with it. If your charger supports it, use a slower one at night and save the fast brick for the ten-minute top-up before you leave.

Wireless charging, cheap cables and other small decisions

Wireless charging is convenient and slightly worse for longevity, because inductive transfer wastes energy as heat directly against the back of the phone. A phone on a wireless pad all night is warmer than the same phone on a cable. Not a disaster, but if you have a choice, cable it.

On chargers themselves: brand does not matter nearly as much as certification. A properly certified USB-C charger from any reputable maker is fine. An unbranded £3 brick with no safety marking is the one genuine fire risk in this whole discussion, and it is a real one. Buy from a seller you would trust with the phone itself.

So what should you actually do?

If you want the simple version: keep charging overnight, turn on your phone’s optimised charging setting, take the case off, and use a slower charger at night. That gets you nearly all of the benefit for zero daily effort.

If you want the optimal version: charge in the evening while you are awake, unplug around 80%, and top up in the morning. Better for the battery, mildly annoying in practice.

And keep some perspective. Battery degradation is real but gradual, and a phone kept three years with sensible habits usually still holds 85-90% capacity. Apple publishes clear figures on this in its battery performance documentation, and Battery University’s technical write-up is the best free explanation of the underlying chemistry if you want the detail.

Whether you charge your phone overnight or not, the settings matter more than the timing. For more on squeezing life out of a handset, see our guides on keeping iPhone battery health high and Android battery saving tips, or browse everything on the Tips & Tricks homepage.