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and cables themselves, and while they're definitely more than good enough reasons by themselves to avoid uncertified cables and chargers, unless the cable sets your couch on f ire, they're not going to cause your iPhone to explode. So how does iPhone charging actually work and what are the risks of using uncertified cables and chargers? Read on to find out... 4. You Can't Overcharge an iPhone Assumptions that you can "overcharge" an iPhone are based on a fundamental misunderstanding of how electricity works. Electrical charging current is never pushed to a device. In other words, your charger doesn't "force" power into your iPhone. It supplies power, which the iPhone draws on, or "pulls" from the charger. This means that an iPhone can never get more current than it needs, regardless of what charger you're using, since there are power regulation chips in the iPhone itself to determine how much power is being drawn from the charger and fed into the battery. Once an iPhone is fully charged, it simply stops drawing any thing more than a trickle of power to run from. In fact, even at about 80 percent capacity, the iPhone slows down charging, and with iOS 13's Optimized Battery Charging feature, the iPhone will actually cut of f charging at the 80 percent point if it knows it still has time to get there later in order to prolong the life of your batter y, since lithium-ion batteries don't like to be continually kept at full capacity. Contrary to a popular misconception, however, with standard USB none of this is based on a "negotiation" with the charger — there is no intelligent back-and-forth communication involved where the iPhone "tells" the charger what to do. Instead, it's simply electricity 101 — it's the same reason that the light bulbs in your house don't explode even though they're on the same circuits that are capable of delivering enough power to run a block heater, air conditioner, refrigerator, or a microwave oven. The light bulbs draw the power they need from the circuits, and nothing more. This is also why you can always use a higher- current charger. For example, for many years, Apple's iPhones could only charge at five -watt (1A) speeds, yet you could safely use a 12-watt (2.4A) iPad charger to charge your iPhone. The iPhone draws only the power it needs from the charger. Keep in mind, however, that there is a slight risk in going in the other direction — using a lower-current charger to charge an iPhone. Although Apple's power regulation chips tr y to determine how much power they can draw from a charger, if the charger or cable are improperly designed, the iPhone can tr y and draw too much current, resulting in the charger overheating as it tries to keep up with the iPhone's demands for more power. This will definitely cause the charger to get hotter, and depending on how badly designed the charger's circuitry is, could even cause a f ire. To be clear, however, this kind of voltage regulation isn't an Apple thing — it's part of the USB batter y charging specification. All USB- certified chargers devices are supposed to be able to let the device on the other end determine what level of power can be supplied, and only draw that amount of power and no more. So in other words, you don't need to buy an Apple-certified charger — any USB-certified charger will handle this just fine. 3. Voltage The discussion above only talks about charging current (amperage), but there's another factor worth considering, and that's the voltage of the charger. This is what's most likely to get you in trouble, since if you were to connect, say a ten-volt charger into your iPhone (which expects five volts), that would almost certainly damage your iPhone — possibly irreparably. It still wouldn't overcharge the batter y or cause an explosion, although it would almost certainly burn out the charging circuits between the Lightning port and the batter y. You might even see smoke or smell burning if you tried such a thing. That being said, in over two decades of working with USB power adapters, I have never encountered one that doesn't provide five volts. A company would have to be completely out of touch with reality to release a USB charger that far out of the USB spec, which requires that ever y thing USB be five volts and only five volts. What you're more likely to encounter in a cheap USB charger is poor voltage regulation. This means that it may not provide a "steady" five volts, but could shift around between, say, 4.5V and 5.5V. This will not cause noticeable damage to your iPhone — most electronic devices are designed to handle this kind of variance — but it may affect your charging efficiency, and could even shorten the life of your battery compared to using a proper charger that stays within proper tolerances. 2. The X-Factor: USB-C PD ("Fast Chargers") So far we've only talked about standard USB chargers, but there's a big exception with the new kid on the block: USB- C Power Distribution chargers, or "USB-PD." These are the "fast chargers" that you can buy for more recent iPhone models, which use Apple's Lightning to USB- C cable, and in fact this is what comes in the box with Apple's new iPhone 11 Pro models. The rules for a USB- C PD charger are very different from standard USB, since the USB-PD spec includes several "power profiles" that of fer charging at different voltages depending on what the device wants. This means that with USB-PD, the iPhone does need to negotiate with the charger to arrange the proper charging power — both current and voltage. If a USB- C PD charger wasn't