Should I charge my phone on AC or DC?

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Closed last year.

I had been wondering why do we need AC to charge our phones and not DC?

Can someone please give me a detailed answer for this?

iPhones run and charge using DC power. If you're using an AC power adapter, that's just an AC to DC conversion.

If it's connected, it will draw as much power as it needs from the external power supply. If there's any extra, that can go to charging the battery. If it needs more current than that, it will draw it from the battery. It won't switch to using it from the external power source, but will use that source first.

And yes you could have an iPhone battery last longer if usually connected to some sort of external power supply where it's not going through constant charge-discharge cycles. It would still go through cycles as there may be periods where the battery is needed for supplemental power as well as the battery self-discharging. But for the most part the battery finishes charging and then stops charging. The power management system will wait for the state of charge to drop to a certain level (remember the self-discharge and supplemental power draw) before it will start charging again. However, this doesn't particularly show up on an iPhone. It will display 100% charge, even though it might have lost 5% of the available charge.