The quest to make the fastest charging smartphone

by Peter Griffin / 05 December, 2018

R17 Pro phones are stress-tested to check screen quality. Photo / Peter Griffin

When it comes to the features you need to weigh up when choosing a smartphone - camera quality, screen resolution, processor speed, you can add a new one to the list - battery charging speed. 

Most modern smartphones have enough juice in a full charge to get you through a day’s usage - if you are doing fairly standard things like web surfing, playing music or brief stints watching videos.

But many of us are using the device in our pocket to do so much more - binge watch Netflix shows, take photos, tether the phone to use as a wi-fi modem, often all at the same time. That is why you increasingly see people toting around a battery bank to top up their phone battery on the move.

The rise of fast charging

“We needed to solve this urgent problem and provide fast-charging technology to our users,” says Shebiao Chen, a hardware engineer at smartphone maker Oppo, based in Dongguan, China.

Most new high-end smartphones now feature technology allowing you to charge your phone at an accelerated pace to what you have traditionally been used to. The idea is that if you can plug in even for a short burst of charging, you’ll boost the battery enough to see you through the rest of the day.

Check out Noted’s guide to buying a wireless charging pad for your phone

The new Oppo smartphone, the R17 Pro ($999) can get from zero to 40 per cent charge in 10 minutes and is fully charged in around 35 minutes. Its predecessor, the R15 Pro, took 90 minutes to get to full charge.

That makes the R17 Pro the fastest-charging phone currently on the market, along with its stablemate, the Find X Lamborghini edition ($2,400), Oppo’s luxury handset.

Some phone makers have licensed fast-charging technology from third parties, such as Qualcom’s Quick Charge or the USB-PD standard used in Apple handsets from the iPhone 8 onwards. Others, such as Samsung, Huawei and Oppo have developed their own proprietary fast-charging technology, seeing the feature as integral to the appeal of a new handset.

Smartphone maker Oppo uses SuperVOOC fast-charging technology in its latest R17 Pro smartphone. Photo / supplied

In Oppo’s case, the technology is called SuperVOOC, a supercharged version of so-called Voltage Open Loop Multi-step Constant-Current Charging, which initially launched in 2014.

“VOOC is low-voltage flash charging,” explains Chen, whose name appears on some of the 700-odd patents Oppo has secured in fast-charging technology.

“You can charge the phone any time, even while you are using it. There's no overheating. With high-voltage flash charging, you can only charge when the screen is off. It also has heating problems.”

How Oppo achieves such fast-charging speeds comes down to clever engineering but plays to the strengths of battery physics. Increasing voltage in a charging system allows a battery to charge faster. But there are limits to doing so safely and without generating excessive heat which eventually limits the charging speed.

The industry has been trying to achieve faster charging with higher voltage. But Oppo instead looked at the flow of electricity, or current, measured in amps.

“After a lot of research, we found that keeping the voltage level the same and increasing the current level was the best way. It is very safe and fast and provides the best user experience,” says Chen.

It involved re-engineering the battery used in SuperVOOC phones. Instead of one big battery, the R17 Pro has two battery cells that charge at the same time, splitting the voltage and current between them. Overall, the batteries are 3 - 5 per cent smaller than one big battery due to the extra connectors needed.

What are the downsides? Producing a larger number of smaller lithium-ion cells can be more costly and the system only works if you use the phone’s SuperVOOC-compatible charging adapter and cable, which have been specially engineered for the purpose.

Fast charging can also degrade a battery’s lifespan faster than regular charging. But Chen says Oppo can guarantee that battery capacity of 80 per cent is maintained after 800 cycles (charging and uncharging the battery 800 times).

With the Samsung Note 7 exploding battery debacle still a vivid memory for the industry, you can understand why Oppo’s rivals have been more conservative on battery technology. Apple, for instance, claims that fast charging will refill up to 50 per cent of an iPhone battery in 30 minutes, slow compared to Oppo and Huawei. Apple owners also need to invest in a MacBook charger and USB-C cable because a fast charger doesn’t come as standard with a new iPhone.

“VOOC is very safe,” says Chen.

“When we find the temperature passes a certain limit, the VOOC function will be turned off to guarantee the user is safe.”

So how fast can smartphone charging actually yet? The question is one Chen’s engineering team thinks a lot about, but he isn’t giving anything away. He points to a demonstration Oppo gave in 2016 at the Mobile World Congress in Barcelona, where a relatively small 2,500mAh (milliamp hour) battery was charged from zero to 100 percent in 15 minutes.

That’s a lower-capacity battery than exists in the R17 Pro (two 1850mAh battery cells), but if the low-voltage charging can be scaled up for larger battery systems, we could see a revolution in charging that may extend to larger gadgets, such as laptops and vacuum cleaners as well as smartphones.

Meizu, another smartphone maker based in Guangdong, claims it can fully charge a larger 3000 mAh battery in 20 minutes with its mCharge system. The developments will no doubt spur the likes of Apple and Samsung to up their game on fast-charging.

Both phone makers have also pursued wireless charging as a feature in their handsets, something that is so far absent from Oppo devices. Chen says the technology isn’t compelling yet, compared to the fast-charging gains of SuperVOOC.

“We are evaluating the technology. Currently, we can achieve 15W (watts) fast wireless charging,” he admits.

“When the user experience is good enough and when the technology has matured, we'll release it.”

Peter Griffin visited Oppo in Guangdong as a guest of Oppo.

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