Difference between normal charger and Dash charger

If the battery power does not grow, it must be possible to charge faster - that is the motto of the device manufacturers. And that's why companies like Samsung, OnePlus and Oppo have long since stopped relying on the USB standard, instead using fast charging to pump significantly more power through the copper wires towards the smartphone. I will show you in an overview which technologies various manufacturers are currently using and how they differ.

Fast charging: how technology came about

It wasn't that long ago that a smartphone had to charge all night to get back to a battery level of 100 percent. However, there were also less energy-hungry background apps running on the devices, which drained the phone faster. Over the years, that has changed a little: In the meantime, a device often synchronizes several e-mail accounts, various social networks, loads information for smart assistants and offers an always-on display even in deactivated mode. This pulls on the small batteries that ensure sufficient power supply in smartphones. However, the end here is quicker than one would like. And because new battery technologies are a long time coming, the device manufacturer had to come up with a different solution: The battery had to be charged faster in order to at least make the power breaks at the mains plug as bearable as possible.

A short digression into cell physics

A smartphone battery has been equipped with the same chemistry for years, regardless of whether it is a Samsung or Apple smartphone. The abbreviation "Li-Ion" will always be legible on the label of the battery. This is short for lithium-ion: the positively and negatively charged electrodes are separated from each other by a separator. If energy is requested, positively charged lithium escapes from the positive electrode in the cobalt-oxygen layer and "changes" to negatively charged graphite.

Now there is a disadvantage with the Li-ion batteries: You can either trim the battery for performance so that it has a high discharge speed. This is the case with model building batteries, for example. Or one optimizes in the direction of capacity, so that as many kilowatt hours of energy as possible can be pressed in the smallest possible space. Smartphone batteries are more likely to be found in the second category. Unfortunately, the previous lithium polymer batteries have already reached their maximum energy density. Because of this, material is sometimes stuffed into the battery down to the last millimeter, which, as is well known, sometimes did not go well.

Fast charging in theory

Let's go a step further on the charging and discharging speed. While the capacity has almost doubled in recent years, the theoretical maximum load on the batteries has decreased. This load was never exploited, but now it's getting exciting: The possible loading speed has increased.

In model making, the so-called C-rate is used: 1 C corresponds to the stored power of a battery in ampere-hours. If a battery were to be charged with a C, it would be full after an hour. For lithium-ion batteries, 1 C is usually a charging speed that does not harm the chemistry of the battery. I would like to theoretically calculate how a 3,000 mAh battery with a nominal voltage of 3.8 volts could be charged - these are two common sizes in the smartphone market.

Based on the normal USB connection, which supplies 5 volts and 0.5 amps, the battery would need 5 hours and 56 minutes for an ideal charging process without losses with an average voltage of 3.8 volts. USB 3.0 delivers at least one ampere, which results in a charging time of around 3 hours. We want to keep this calculation for the fast charging of smartphones.

Quick Charge: Qualcomm's quasi-standard

With Quick Charge, the manufacturer, whose mobile processors are in pretty much every high-end smartphone, has achieved a monopoly position: The technology is only compatible with the Snapdragon processors from their own company, such as those found in the Samsung Galaxy Devices or from HTC, HP, LG or Asus. Some mid-range CPUs also support the technology, such as the Snapdragon 617 or 627.

The technology relies on communication between the charger and smartphone. If the processor recognizes that the charger supports Quick Charge, an exchange takes place via the data line and the clever charging mode is activated. Quick Charge 2 then simply increased the voltage and amperage, which of course allowed the phone to charge faster. With the current Quick Charge 3 standard, Qualcomm introduced "INOV": With the "Intelligent Negotiation for Optimum Voltage", the phone and charger can communicate bilaterally and regulate the voltage with an accuracy of up to 0.2 volts throughout the entire charging process.

Surnamenominal voltageAmperageMaximum charging poweradvantages
Quick Charge 1.05 volts2 amps10 wattsFaster than USB
Quick Charge 2.05, 9 or 12 volts, static2, 2 and 1.67 amps18 wattsMore volts: higher efficiency
Quick Charge 3.02.6 to 20 volts, dynamic in incremental 200mV steps2.5 and 4.6 amps18 wattsIncremental control: less waste heat, optimization
Quick Charge 4So far unknownSo far unknown28 wattsUSB Type-C mandatory, 5 minutes: 50% capacity
Quick Charge 4+So far unknownSo far unknownSo far unknown15% faster, 15% cooler, 20% more efficient

Quick Charge 4.0 is officially supported by the current Snapdragon 835. The Samsung Galaxy S8, as one of the few smartphones that already has this processor installed, does not yet use fast charging - probably because the software is not quite finished yet. However, the feature may be submitted as a software update at a later date.

Throttling at high temperatures

Incidentally, our theoretical battery from the above example would be full after around 50 minutes when fast charging with Quick Charge 3.0. This is of course not true, which is why I will stop this example at this point. There are two general explanations for this: The optimal charging process for a Li-Ion battery looks like a logarithmic curve. While this is negligible with low charging currents, 18 watts is quite a lot with such small batteries. That is also the reason why Qualcomm advertises with the slogan "50 percent in 30 minutes" and not with 100 percent in an hour. In the less charged percentage of the battery, the charging curve almost completely corresponds to the ideally calculated charging time, with more percentages the curve flattens noticeably and the battery fills more slowly.

In addition, some of the electricity is converted during fast charging - in the form of waste heat: The process of converting the electricity from the cable into charging current for the battery is lossy. Around 15 to 20 percent of the energy is converted into heat that warms the smartphone up to 40 degrees. From this temperature onwards, Quick Charge automatically throttles the charging current, which protects the device from damage.

VOOC Flash Charge: Oppo solitary confinement

The Chinese manufacturer Oppo is taking a slightly different approach. The so-called VOOC Flash Charge does not rely on higher voltage, but on higher currents. So the voltage remains at the typical USB 5 volts, but 4 amps are chased through the cable during fast charging. According to Adam Riese, a maximum of 20 watts of charging power is possible.

According to Oppo, around 75 percent of the battery is filled again within 30 minutes. These are of course laboratory conditions, but VOOC is a bit more fixed on paper than Quick Charge 3.0. The temperature of the smartphone remains significantly lower compared to the competition: Since the voltage does not have to be converted particularly strongly, the device can stay colder despite fast charging. The heat development on the charger is a bit higher.

However, Oppo’s technology has a notable disadvantage compared to Qualcomm’s solution: Due to the high currents, a special cable is required, as not every USB cable supports VOOC. This is because higher currents require larger wire cross-sections in the cable - otherwise the resistance is too great, which is expressed in the fact that the cable becomes warm and a few watts of power are lost on the way to the smartphone. If VOOC did not take this precautionary measure, it could even lead to cable fires in the worst case.

VOOC Flash Charge almost irrelevant on the German market

Similar to Quick Charge, the charger and smartphone communicate with each other; the data line exchanges the necessary parameters. This can then lead to pairing and fast charging. To prevent damage to the smartphone, Oppo even built in a fuse that could cut the connection in an emergency. In the worst case, high amperages are more dangerous than higher voltages.

Surnamenominal voltageAmperageMaximum charging poweradvantages
VOOC Flash Charge5 volts4 amps20 wattsLess heat development, 75% in 30 minutes
Great VOOCNot knownNot known~ 40 watts2500 mAh charged in 15 minutes, not yet in use

Oppo does it in a similar way to Qualcomm: Only smartphones of its own brand are allowed to use the charging standard. That is why VOOC Flash Charge is almost irrelevant on the German market. Only the following are supported:

  • Oppo R11, R9 and R7 in all versions
  • F1 and F3
  • Find 7 in all versions
  • N3

Dash Charge: Pretty much the same

Most of you will have nothing to do with VOOC Flash Charge. But maybe you are using a OnePlus device? Then you will be able to use the same advantages as VOOC Charge with Dash Charge. Because Dash Charge is - except for the name and small subtleties - exactly the same as VOOC. However, OnePlus compromises from the original. Around 60 percent should be charged within 30 minutes. Three of the OnePlus devices are currently compatible with Dash Charge: The OnePlus 3, 3T and also the new OnePlus 5 use fast charging technology.

Dash Charge also requires a USB Type C charging cable for fast charging, which can transport the high currents from point A to B. You can choose to take the cable from the scope of delivery or choose one of the supported cables for Dash Charge. With a normal cable, the charging process takes longer because it does not charge 4 amps.

Surnamenominal voltageAmperageMaximum charging poweradvantages
Dash Charge5 volts4 amps20 wattsLess heat development, 60% in 30 minutes

SuperCharge: Not Tesla, but Huawei

Huawei does not have a global supercharger network. Thanks to SuperCharge, the manufacturer's smartphones charge faster than Tesla's cars. With the so-called SCP chip in the charger and the smartphone, both devices communicate with each other with this charging standard. SuperCharge goes one step further than VOOC Flash Charge: Instead of sending 5 volts, Huawei goes straight down to 4.4 volts. This corresponds to the maximum voltage of the battery with which it consumed 100 percent of its power. With fast charging, this ensures that electronics no longer have to reduce the voltage in the phone itself, but that the energy can be loaded directly into the battery.

Since the internal voltage converter of the smartphone with SuperCharge has no work, it does not get warm either - this means the device stays cold. At 4.4 volts, the charging standard transports 5 amps through the USB-C cable, which corresponds to 22 watts of power. According to Huawei, a 20-minute charge is enough for a full day of use of the corresponding Huawei mobile phone.

Also with SuperCharge it is said again: A special cable for fast charging is needed. The high currents do not allow a generic cable, as this could lead to cable fires. SuperCharge is compatible with the Huawei Mate 9, the P10 and P10 Plus; according to tests, the Mate 9 is fully charged after 111 minutes.

Surnamenominal voltageAmperageMaximum charging poweradvantages
Super batch4.5 volts5 amps22 wattsElectricity goes directly into the Li-Ion battery

Pump Express: MediaTek's solution

MediaTek, as Qualcomm's biggest competitor, can of course not use the Quick Charge technology. And as it is, there must be a comparable offer from MediaTek, otherwise there would be a unique selling point. MediaTek offers the alternative under the name Pump Express. The third generation does not have to hide in terms of performance: Similar to SuperCharge, MediaTek bypasses the internal circuits of the smartphone and charges the battery directly to its maximum possible 4.4 volts. With Pump Express 3.0, the battery reaches around 70 percent of its total capacity after just 20 minutes of fast charging, and nobody is even faster on paper.

Very few devices currently support Pump Express 2.0, including the Meizu MX6. The Pump Express technology has only been renamed here and is called mCharge on the MX6. So far there is no smartphone on the market that supports the third revision, although MediaTek predicted corresponding devices for the end of 2016. The basic requirement for Pump Express 3.0 is the latest MediaTek chip, the Helios X20, which is already installed in some smartphones. Perhaps a software update can help here in the future.

Surnamenominal voltageAmperageMaximum charging poweradvantages
Pump Express5/7/9/12 volts3 amps20 wattsFaster than USB
Pump Express 2.05-20 volts, dynamic in incremental 0.5V steps3 amps25 wattsVolts depending on cable quality. Low quality: higher voltage
Pump Express 3.03-6 volts, dynamic in incremental 10mV steps5 amps24Electricity goes directly into the Li-Ion battery, 70% in 20 minutes, full after 75 minutes

Charging the battery: it lives a lot longer

Each manufacturer does its own thing. Nevertheless, there are some tips that you can follow when charging in order to save the battery and still be able to fill it up faster:

  • Airplane mode on and background applications ended: If any wireless connection is interrupted, programs cannot transmit to the outside world. This reduces the load on the cell phone
  • Do not use while charging. It is best to leave the phone on its side, because even light loads can slow down the charging process enormously
  • Get out of the sun! Ideally, charge mobile phones in shady and colder surroundings - because a battery will be damaged from a temperature of 45 degrees, which is reflected in shorter runtimes and bloated jaws
  • Conditioning the battery? This is not necessary with current batteries, the so-called memory effect no longer occurs
  • As early as possible to the socket? In general, the following applies: The smartphone battery has a longer life expectancy if it always has a charge level between 30 and 80 percent
  • Don't store your smartphone full? That's right. The ideal storage voltage of lithium-ion batteries is 3.85 volts, which corresponds to about 30-40 percent battery charge. In this storage condition, there is the least risk of explosion. In addition, the cells lose less power in the long run than when they are fully charged

Images by Mika Baumeister


About Mika Baumeister
Mika is studying technology journalism in Bonn and has been writing about all sorts of technical odds and ends for some time: be it smartphones, gadgets, drones, VR glasses or applications of all kinds. In principle, with every article he turns his hobby into a job.

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