The Be-All, End-All of USB Charging FAQs (For Now)

RAVPower USB Charging FAQ USB Guide Help

Q: What’s the difference between 05.A, 1A and 2A/2.1A USB charging?

 A: Let’s start with a softball question. The A in 0.5A, 1A and 2.1A stands for Amp(s). Amps, or amperes, measure electrical current. In general, more amps = faster USB charging. Most modern smartphones require a minimum of 1A to charge properly, and are equipped to take advantage of 2A+ cables. If you have an older battery, however, you may not see superior performance from a higher amp cable because the battery is only equipped to handle a certain amount of current at a time.

A new challenger has appeared in the world of USB charging. USB Power Delivery (USB PD for short) goes way beyond amp counts of course, and is as a topic worthy of a blog of its own… which is why we wrote one. Check that post here!

USB Charging Cable Quality RAVPower iPhone MacBook USB 3.1 USB 3.2

Q: What’s the difference between USB 1.0, 2.0, 3.0 etc.?

USB is an industry standard for connection and power supply. As technology improves, the quality of USB must also improve. That’s why the USB Implementers Forum regularly releases version updates. Introduced in 1996, USB 1.0 is a fossil, capable of just 12Mbit/s data transfer—by comparison, USB 3.2, which was just introduced in September 2017, can hit 20Gbit/s.

Basically: the higher (i.e. more recent) the version number, the better. For insider information on choosing the right USB quality, check our USB cable quality guide.

Lightning Cable USB Power Delivery Qualcomm 3.0 QC3.0 USB-A USB-B USB-C Type-C USB

Q: Why are there so many differently shaped USB cables?

This was more of a nightmare for users five or six years ago, but those with older devices can still find themselves in a bind if they lose the USB charging cable that came with their phone. We’ve all had to try to eyeball whether a cable in a box at the electronics store is the same shape as the port we need—and with Apple’s continued insistence on their proprietary Lightning port, iPhone owners are still estranged from the rest of the smartphone family.

Today, thankfully, there are basically only three common cable types:

  • USB Micro: Micro connectors are designed to stand up to many, many insertions and removals, essential for the busy work of charging phones. They’ve largely replaced the boxier USB Mini Just to make you extra sad though, there are Micro A- and B-type connectors, but virtually all new micro-compatible phones now use Micro B.
  • USB-C: We have a whole post on USB-C cables in which we call them the future of USB cable charging so we’re a little excited about them, yes. Their main benefits include reversible charging, which allows both bidirectional power exchange (meaning you could potentially charge your computer with your phone, or share your phone’s power with a friend who’s out). They’re also likely to become the standard in the near future.
  • Lightning: Apple’s likes to keep tight control over its supply chain, so its products use their own standard. Although the technology is distinct, its use is identical in most regards to USB, and new MacBooks do support USB-C as well.

USB Cable Connector Types USB-C USB-A Micro-USB Mini-USB Lightning Cable

Q: What is iSmart 2.0 USB charging?

Batteries have chips that allow them to regulate the amount of current they receive from USB charging devices. They do this both to optimize charging speed and to prevent damage to the battery from overcharging. iSmart 2.0 is part of a new generation of USB charging units that intelligently manage this exchange from the delivery end:

  • Automatically delivers most efficient power output based on specifications of the device being charged
  • Corrects charging irregularities caused by older ports and cables
  • When multiple devices are connected to an iSmart 2.0 portable charger, it optimizes its output to each
  • Provides surge, temperature, EMF protection and more

Similar power management concepts fuel Qualcomm’s Quick Charge (QC) line, which enables devices to request variable amounts of voltage from the power source based on its needs. This improved efficiency means batteries can be charged with QC 3.0 in 35 minutes—compared to 270 minutes for conventional chargers. Read our post on why QC 3.0 is an evolutionary leap over 2.0.

RAVPower iSmart 2.0 Adaptive Charging Technology Cartoon

Q: If wireless charging takes longer than other standards, why is it so popular?

We actually have a whole post on this topic, so if you want to take a deep dive into wireless charging start there. USB charging is still far and away the fastest way to fill your battery, but there are other considerations. The main benefit here is convenience. Wireless charging is rapidly improving with 10W speeds. Plus we’re already starting to see smart desks with built-in pads so you can just leave your phone on the desk overnight and when you pick it up, it’ll be charged. Therefore, you don’t need to worry about plugging it in, or battling over limited outlet space.

It’s also safer than using a cable, as induction charging eliminates the possibility of sparks and jolts. Not that that’s as common as believed.


Any more questions?

 In the interest of brevity we’ll close this FAQ here, but we’re not going anywhere. Do you have any USB charging questions? If so, ask us in the comments and we’ll do our best to untangle your questions about cables (and questionable cables)!

17 Replies to “The Be-All, End-All of USB Charging FAQs (For Now)

  1. What happens if the charging cable for the battery pack is plugged in to the DC out for an extended period of time? I have a RP-BP14.

    1. The power bank will automatically turn off once it detects that the battery is fully charged. However we don’t suggest you always leave it plugged in for extended periods of time.

  2. I see power strips and desk lamps among other things which you can plug a USB-to-USB-C cord into. Are these safe ways to charge our phones?

  3. i have searched a whole lot and cant find what i was looking for, could you specify the maximum outputs for a 3.2 gen 2 type A port as well, i know type C has an output of max 100W, And does the device can draw out power from 5w to 100w like they need or its basically like 5v2a and so on , i have a phone which needs 22.5w so in what rate will the device inputs the power from a PD port ?
    I cant find these differences anywhere so have asked

  4. What happens if I plugin two devices that can operate at 9V/2A (or 5V/3A and 5V/2.4A respectively) into a dual port 18W charger. Will they both receive 9V/1A or 5V/1,8A or different? And what happens if I use a 30W dual port charger for the same two devices?

  5. I have the RP-PB232. I have a miniPC (MeLE Quieter2) that does not have the hardware for the PD standard. I am going to use a converter that inputs power from a PD charger or bank and puts out a constant 12 volts to power the MeLE. See here – ( I want to use the iSmart port (max 1.5A, 12v). I will keep the MeLE power consumption less than 1.5A. ALSO, I WOULD LIKE TO simultaneously use the PD Port of the RP-PB232 to power the Peltier cooler on an astrophotography camera (Zwo ASI533MC). The 533 uses a barrel plug connection for power and expects 12v. It can take up to 3A but I will not use the max cooling, so should be more like 2A. It also does not use the PD standard. I intend to use the same type of 12v converter for a constant 12v. As the camera is rather expensive, I wanted to check with you that the constant 12v from the PD converter would be safe (I can check it with a voltmeter before use; I think it should be safe).

    1. Hi Alan, the iSmart Port needs to use the QC trap. The link is the PD trap, which can only be connected to the PD port. There is no problem in power allocation. When two ports are output at the same time, the maximum PD is 65W, and the maximum QC is 18W. Whether the voltage is safe mainly depends on whether the voltage of the trap is normal.

  6. Hi! Does RAVpower produce any chargers that can put out 4.5A current (PPS)? I hope so!

    The Note10+ asks for 4.5 amps at 10 volts to get 45W. It does NOT work with 15v @ 3 amps.

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