Wall charger voltage. Apple 2.4A

The Complete Guide to Charging the Chevy Volt

The Chevy Volt is the best-selling plug-in hybrid electric vehicle (PHEV) of all time: more than 130,000 have been sold since its release in 2010. Early models offered about 40 miles of all-electric range, while the latest Volt has 53 miles. Both are more than enough for most drivers’ 30 miles a day of driving needs.

Being able to drive electric most of the time, but access the convenience of gas when needed, has helped many people make the switch to electric, including me. I’ve been the proud owner of two Chevy Volts: I loved driving my 2013 Volt for several years, then traded it for a 2016 Volt (Gen 2). Since then, I’ve also added a 2017 Chevy Bolt EV to my garage, and I can say without equivocation that these are some of the finest cars I’ve ever owned.

Why Choose a Plug-in Hybrid?

Plug-in hybrids have a gas engine and an electric motor, so they can plug in to charge the battery, but can also run on gas only when needed. If you want to drive electric most of the time to reduce your emissions and save on fuel costs, it’s very possible. For example, it’s December 2017 and the last time I bought gas for my Volt was on Valentine’s Day! (I just want to know: does gasoline spoil?) If you want to try going electric but don’t have access to charging at home or work and want to take long trips without charging, a hybrid may be a good choice.

With a Volt, you can top off the battery anytime you’re parked, at home or around town, instead of making a separate trip to refuel. Topping off your Volt helps give you as much range as possible and makes each charging session shorter. It takes just a few seconds to plug in, and then you can go about your day (or night) while your Volt gets some charge.

Charging Your Chevy Volt at Home

Charging a plug-in hybrid at home is not much different from charging your cell phone or laptop. Just plug the cord that comes with the car into a regular wall outlet to add about 4 miles of Range Per Hour. It will take about 12 hours to recharge your Chevy Volt this way. If you don’t have 12 hours available every day to recharge or want to be able to make multiple longer trips in a day, upgrading to a Level 2 home charger makes sense.

One difference to note is that many plug-in hybrids like the Volt have a slower onboard charger (what converts AC power from an outlet to DC power for the battery) than battery electric vehicles, meaning these hybrids can add only about 12 miles of Range Per Hour with even a 32-amp Level 2 charger (that’s compared with the 25 miles of Range Per Hour most battery electric vehicles can add). Still, getting a faster Level 2 charger will prepare you get an all-electric vehicle eventually, like I did.

If you don’t live in a single-family home, we’d love to help you get EV charging at your apartment or condo. A hybrid can be a great choice if you can’t charge at home because you’ll have a gas tank if you really need it. You can live the EV lifestyle with any car if you charge at work or Level 2 stations around town. Check the ChargePoint app to find places to charge near you.

Charging Your Chevy Volt at Work and Around Town

They can be hard to spot if you’re not an EV driver yet, but there are likely plenty of charging stations at nearby workplaces, restaurants, retail stores and other places you spend time (confession: I charge here at work). These locations usually have Level 2 stations with a universal connector that can add about 12 miles of Range Per Hour to your Volt.

The best part about charging around town is that you can go about your day while charging, instead of waiting around for your EV to refuel. Discover places to charge near you in the ChargePoint app and just tap your phone or use the ChargePoint card that comes in the glovebox of the Chevy Volt to start charging.

How To Choose The Right USB Wall Charger

So you need a new USB wall charger for your phone? Maybe your device didn’t come with one out of the box, a trend that is growing with phone manufacturers. Charging a phone is simple enough, but the sheer amount of charging standards, cables and optional fast charging don’t help to make the process of choosing the right charger any easier. Luckily, we are here to help to make the decision easier for you with our own range of wall chargers to choose from here. Let’s break down some of the key information you need when shopping for a reliable wall charger.

Find out how much power you need (W)

When considering a USB wall charger your first concern is how much power your device needs to charge effectively. This will often list the very maximum charging power a given device is capable of. You can turn to the manufacturer’s website/spec sheet for this. In general, smartphones require between 18 – 120 W (watts) of power.

In general, there are three smartphone charging standards, and these are:

  • Universal – USB Power Delivery (USB PD): the most common USB. C charging standard for phones.
  • Proprietary – OEM-specific charging standards: Limited to manufacturer products which may offer exclusive fast charge technology which you won’t find in third-party plugs.
  • Legacy – Pre. USB. C: outdated and slowly being phased out, usually found on older lower powered phones.

So the key to correctly choosing a wall charger for your phone that will charge at the fastest possible speed is ensuring enough throughput wattage whilst supporting the required charging standard.

Consider the number of charging ports supported

It’s important to bare in mind the use case for your wall charger before purchasing. Futureproofing is key, do you solely need your charger for one device? Perhaps you wish to be able to charge two portable devices at the same time such as a phone and a tablet. Consider your use case carefully to maximise the usefulness of the charger you purchase and check that it has the correct USB ports required for your device cables.

Input/output control, voltage regulation, and overheat protection, are all safety features that should be a baseline consideration when choosing your wall charger. These will regulate power in and out of the charger, prevent short circuits and ensure that your charger will not overheat. Without these, your wall charger or connected devices could be damaged, or in the worst-case scenario cause a fire. All GP wall chargers come with cutting-edge safety features as standard for peace of mind.

Inside a charger

These chargers cram a lot of complex circuitry into a small package, as you can see from the iPhone charger below. (See my iPhone charger teardown for more details.) The small size makes it challenging to make an efficient, high-quality charger, while the commoditization of chargers and the demand for low pressure manufacturers to make the circuit as simple as possible and exclude expensive components, even if the power quality is worse. The result is a wide variation in the quality of the chargers, most of which is invisible to the user, who may believe a charger is a charger.

Internally a charger is an amazingly compact switching power supply that efficiently converts line AC into 5 volt DC output. The input AC is first converted to high-voltage DC. The DC is chopped up tens of thousands of times a second and fed into a tiny flyback transformer. The output of the transformer is converted to low-voltage DC, filtered, and provided as the 5 volt output through the USB port. A feedback mechanism regulates the chopping frequency to keep the output voltage stable. Name-brand chargers use a specialized control IC to run the charger, while cheap chargers cut corners by replacing the IC with a cheap, low-quality feedback circuit.[4]

A poor design can suffer several problems. If the output voltage is not filtered well, there will be noise and spikes due to the high-frequency switching. At extreme levels this could damage your phone, but the most common symptom is the touchscreen doesn’t work while the charger is plugged in.[1] A second problem is the output voltage can be affected by the AC input, causing 120 Hz ripple.[5] Third, the charger is supposed to provide a constant voltage. A poor design can cause the voltage to sag as the load increases. Your phone will take longer to charge if the charger doesn’t provide enough power. Finally, USB chargers are not all interchangeable; the wrong type of charger may not work with your device.[6]


Counterfeit chargers pose a safety hazard as well as a hazard to your phone. You can buy a charger that looks just like an Apple charger for about 5000, but the charger is nothing like an Apple charger internally. The power is extremely bad quality (as I will show below). But more importantly, these chargers ignore safety standards. Since chargers have hundreds of volts internally, there’s a big risk if a charger doesn’t have proper insulation. You’re putting your phone, and more importantly yourself, at risk if you use one of these chargers. I did a teardown of a counterfeit charger, which shows the differences in detail.

wall, charger, voltage, apple

I’ve taken apart several counterfeit chargers and readers have sent me photos of others. Surprisingly, the counterfeit chargers I’ve examined all use different circuitry internally. If you get a counterfeit, it could be worse or better than what I’ve seen.

How do you tell if a charger is counterfeit? The fakes are very similar; it’s hard for me to tell, even after studying many chargers. There’s a video on how to distinguish real and fake chargers through subtle differences. You can also weigh the charger (if you have an accurate scale), and compare with the weights I give above. The easiest way to get a genuine Apple charger is fork over 29 to an Apple store. If you buy a 5000 Original Genuine Apple charger on eBay shipped from China, I can guarantee it’s counterfeit. On the other hand, I’ve succeeded in buying genuine used chargers from US resellers for a moderate price on eBay, but you’re taking a chance.

The following picture shows a counterfeit charger that burned up. The safety issues with counterfeits are not just theoretical; when hundreds of volts short out, the results can be spectacular.

Indicated charger type

A device being charged can detect what type of charger is being used through specific voltages on the USB data pins.[6] Because of this, some devices only work with their own special chargers. For instance, an incorrect charger may be rejected by an iPhone 3GS or later with the message Charging is not supported with this accessory.[7]

wall, charger, voltage, apple

There are many different charger types, but only a few are used in the chargers I examined. A USB charger that follows the standard is known as a dedicated USB charger. However, some manufacturers (such as Apple, Sony, and HP) don’t follow the USB standard but implement their own proprietary charger types. Apple has separate charger types for 1 amp (iPhone) and 2 amp (iPad) chargers. HP has a special type for the HP TouchPad.

The point is that USB chargers are not interchangeable, and devices may not work if the charger type doesn’t match what the device expects. The table below shows the type of charger, the current that the label claims the charger provides, the current it actually provides, and the charger type it indicates to the device.

The types of the counterfeit chargers are a mess, as they advertise one power level, actually supply a different power level, and have the charger type for a third level. For example, the counterfeit iPhone charger is advertised as supplying 1 amp, but has the 2A charger type, so an iPad will expect 2 amps but not obtain enough power. On the other hand, the counterfeit iPad charger claims to supply 2 amps, but really only supplies 1 amp and has a 1A type.


People often wonder how much power their charger is wasting while it’s idle, and if they should unplug their charger when not in use. I measured this vampire power usage and found the chargers varied by more than a factor of 20 in their idle power usage. The Samsung oblong charger came in best, using just 19 mW; this was so low compared to the other chargers that I measured it again a different way to make sure I hadn’t made an error. On the other extreme, the fake iPhone charger used 375 mW. The Apple iPhone charger performed surprisingly badly at 195 mW. If plugged in for a year, this would cost you about 21 cents in electricity, so it’s probably not worth worrying about.[8] In the following table, I use the official charger Star Rating System (yes, there actually is such a thing).[9][10]

I also measured efficiency of the chargers under load.[11] One of the benefits of switching power supplies over simpler linear supplies is they are much more efficient at converting the input power to output. The chargers I measured all did pretty well, with 63% to 80% efficiency. The HP charger was the winner here.

The chargers up close

Apple iPhone and counterfeit

The above photo shows a real iPhone charger (left) and a counterfeit (right); the two chargers are almost identical, down to the green dot. If you look closely, the genuine one says Designed by Apple in California, while the counterfeit has the puzzling text Designed by California. The counterfeit also removed the Apple Japan text below the plug. I’ve seen another counterfeit that says Designed by Abble (not Apple). I assume the word Apple is removed for legal or trademark reasons, since the word Apple is often (but not always) missing from counterfeits.

Samsung oblong

I call this charger the Samsung oblong charger, to distinguish it from the Samsung cube charger.

Samsung cube

The Samsung cube charger is shaped very similarly to the Apple iPhone charger. Internally, however, it turns out to be entirely different.

Apple iPad and counterfeit

The photo above shows a real iPad charger (left) and a counterfeit (right). The counterfeit has almost identical text, but without Designed by Apple in California. Assembled in China, Listed under UL, and the manufacturer Foxlink. Inexplicably this sanitization left TM and © 2010 Apple Inc.

The above photo shows a real iPad charger on the left and a fake iPad charger on the right, with the plug removed. The most visible difference is the real charger has a round metal grounding post, while the fake has plastic. (The US plug isn’t grounded, but in other countries the lack of ground in the counterfeit could pose a safety hazard.)

HP TouchPad

The HP TouchPad charger has a very unusual cylindrical shape, which is striking if perhaps not practical. The charger twists apart, allowing the plug to be replaced for different countries. (It took me weeks to discover this feature.)


The Monoprice charger isn’t a USB charger, but instead has a 30-pin iPhone dock connector attached. It is a relatively large charger.

Counterfeit UK

This charger is a counterfeit of the Apple UK iPhone charger. They’ve removed Apple from the text, but left Emerson Network Power, which I’m sure is not the actual manufacturer. The genuine Apple UK charger can be distinguished by a serial number inside the USB connector.

wall, charger, voltage, apple


The Belkin charger eschews the minimal design styling of most chargers, with a roughly oval cross section, curves and ribs, and a cover over the USB port.


The KMS charger is unusual in providing 4 USB ports. It also gives off a blue glow while in use. The plug can be removed and replaced for use in different countries, similar to the iPad and HP TouchPad chargers. I couldn’t find any UL safety approval on this charger, but I did find a report of one catching fire.


The Motorola charger has the lowest listed power output, 850mA. The back of it has a holographic sticker (like a credit card), which may ward off counterfeiters, even though it’s unlikely for anyone to counterfeit this charger. I wonder though why Apple doesn’t use holograms or other anti-counterfeiting techniques, given the large number of counterfeit Apple chargers being sold.

What Is Fast Charging? How Different Standard Works

Fast charging is a popular feature for mobile devices. Including phones, tablets, the Nintendo Switch, and laptops. It allows them to recharge faster over USB connections than they normally would. Newer phones can recharge from 0-50% in 30 minutes. And laptops with USB-C can use an open-source charger.

wall, charger, voltage, apple

The technology on USB dates back to 2007. Added to support the growing mobile market. Since then many charging standards have come and gone. The introduction of USB-C has been a big disruptor. But as plenty of USB-A-based devices remain so do some of the older standards. And a few have crept onto the occasional USB-C port.

How Fast Charging Works

Fast charging works by increasing the voltage and/or current (amps) into your device. This increases the total wattage (volts amps = watts) beyond what a regular USB charger can do. A charging standard handles power “negotiations” between a charger and a device. Verifying both support the same tech. And allowing the device to draw what it wants. But only to the point, the charger can provide. Some standards use similar methods, which allows them to be cross-compatible. Others are quite different and are non-compatible.

In general fast charging offers higher output while the device’s battery is low. The mode operates until the battery reaches 50-70%, depending on the device. As the battery charge increases the fast charging output steps down. This preserves the battery’s lifespan (less stress and heat). This is why charging from 0-50% is fast, while the last 10% seems to take forever.

USB Power Delivery (USB PD)

USB Power Delivery is a power transfer standard introduced alongside USB-C. It is an open standard maintained by the USB Implementors Forum, as is USB-C and other USB standards. All USB PD is USB-C, but not all USB-C is USB PD.

There are three versions of the standard:

USB Power Delivery 1.0

  • Supports 5V, 12V, and 20V. With up to 2A @ 5V and 5A @ 12V and 20V.
  • Supports some power profiles which Power Delivery 2.0 and 3.0 don’t allow for. This was done to include USB-C PD chargers that pre-dated the standard’s release.
  • Rare if buying a new charger today.

USB Power Delivery 2.0

  • Supports 5V, 9V, 12V, 15V, and 20V. All voltages can go up to 3A. 20V can go up to 5A, providing up to 100W of power.
  • For the most part, performs just as well as Power Delivery 3.0.
  • Still common in brand new chargers.

USB Power Delivery 3.0

  • Supports the same power profiles as Power Delivery 2.0.
  • Added programmable power supply (PPS). Which allows for more efficient charging of lithium batteries.

USB Power Delivery allows for increased power levels. Up to 100W, enough to power a 15-inch gaming laptop. Power flow is also bi-directional. The same port can give or take power, with the connection determining what to do.

The dream of many was that USB PD would become the dominant way to charge all future USB-C devices. As an open standard, no one brand would control the market. And one charger (with enough output) could power all your devices. But this hasn’t been the case to date. And whether it’ll happen in the future is up to specific companies, who do not have a stake in the USB-IF.

Power Profiles

All USB-C chargers offer one or more power profiles. These tell us what range of power they can provide. And are the best way to determine if a specific USB PD charger is a good fit for a device. For this explainer, we’ll ignore Power Delivery 1.0. It allowed for some weird power profiles we rarely see in the market.

Power Delivery 2.0/3.0 Power Profile Rules

  • Voltages
  • 5V, 9V, 12V, 15V, 20V
  • If a higher voltage is present, then the lower voltages must also be present
  • 12V is optional under all conditions
  • Each voltage can go up to 3A
  • Current at each voltage should try to match the max wattage, up to the 3A limit
  • 20V can go up to 5A

Here’s an example of two different, but within spec 45W USB-C PD chargers:

Both are acceptable power profiles for a 45W USB-C PD charger. As both offer 15V/3A they must also offer 9V/3A. 20V/2.25A is optional. But if 20V/2.25A is present then 15V/3A must also be present. And again 12V is completely optional.

Wattage vs Power Profiles

Most products list their wattage rather than their power profiles. Watts = voltage current, so 20V/5A = 100W. Knowing the wattage tells us a lot about the available power profiles. If a certain power profile is offered, then certain other ones must also be offered. Assuming the charger is following USB-C specs.

  • 15W = 5V/3A, (9V/1.66A)
  • 18W = 5V/3A, 9V/2A ,(12V/1.5A, 15V/1.2A)
  • 30W = 5V/3A, 9V/3A, (12V/2.5A), 15V/2A, (20V/1.5A)
  • 45W = 5V/3A, 9V/3A, (12V/3A), 15V/3A, (20V/2.25A)
  • 60W = 5V/3A, 9V/3A, (12V/3A), 15V/3A, 20V/3A

The power profiles in parentheses are optional.

To go above 60W a charger offers more than 3A, but only at 20V. So a 100W USB-C charger has the same 5-15V power profiles as a 45W charger. With only 20V offering more output.

When choosing a charger for your device the voltage must match. But the charger can offer more current than the device needs. The device controls the current. Power is drawn from the charger, rather than pushed to the device.

Programmable Power Supply (PPS)

The programmable power supply protocol was added in Power Delivery 3.0. It is an option, so not found on every PD 3.0 charger. It is currently uncommon in both USB-C chargers and devices. But adoption is growing.

It allows for small, step-wise changes in voltage and current. It doesn’t charge a device faster. Instead, it reduces the conversion loss during charging. Making the charge more efficient, which in turn produces less heat. Heat is a key factor in lithium battery lifespan. So PPS is better for your device’s battery.

Under PPS charging occurs in two phases. In the first phase, the current (amps) is constant, with a gradual increase in voltage. In the second phase, the voltage (now at a higher state) is constant, with a gradual decrease in current.

USB-C Specifications

Under section 4.8.2 of USB-C specifications, a proprietary charging method cannot change the voltage of USB-C output (between 4.40V and 5.25V) in a manner not defined by USB methods. Quick Charge and similar fast charging tech operate at higher than default voltages. And so goes against the specifications. USB Power Delivery is an open-source charging method. Created alongside USB-C, it is within specs even though it also increases the voltage. The big difference is USB PD uses communication lines to negotiate power transfer. While proprietary methods take over the data lines for their negotiation. They do so because legacy USB connections, such as USB-A, don’t have comm lines.

There is no known risk with running proprietary charging standards over USB-C. Manipulating the data lines does disrupt data transfers. But when plugging into a wall charger or power bank there is no data transfer anyway. A few USB-C focused engineers warn against using any USB-C product against specs. Their concern is unforeseen consequences. And we have seen bad USB-C products in the past. But since the first Quick Charge over USB-C charger came out in 2016 we haven’t seen any systemic issues emerge.

Leave a Comment