Can Vodafone Pay work when the phone is dead? Depends on how you define 'dead.'

A long-standing complaint about NFC phone payments has been, “What happens when the phone battery dies?” Vodafone has come up with a way around that — albeit with a lot of caveats.

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Since the earliest days of NFC mobile transactions, one of the most oft-repeated criticisms was, "What happens when the phone battery dies?" Well, one mobile payment system says it has solved that problem, but the truth is that it's only solved part of it. Still, something is better than nothing.

On Oct. 10, Vodafone made this claim for its own payment system. "Vodafone Pay can even be used to make a payment when the phone is switched off or out of battery life because the contactless SIM can contact automatically to the contactless terminal to make the transaction," said Vodafone's statement.

But like most things in technology, the truth is a bit more complicated. To understand what Vodafone Pay can and can't do without phone power, it's critical to first define "out of power." For most consumers, "out of power" on their phone means, reasonably enough, that it has stopped functioning. In reality, that merely means that the battery's power level has dropped so low that the phone chooses to not function. This work-stoppage, if you will, is the phone's way of demanding that you plug it into a power source to recharge.

That phone, however, still has residual power, which allows data to be retained and some bare-minimal OS functions, such as the clock, to function. A phone can stay at that level for quite a few days, given that it is then using so little energy.

Vodafone, in a written statement to clarify its technical workings, was more conservative, saying that "mobile phones usually stay in battery low mode for 12h – 24h, depending on battery quality. The remaining power is usually sufficient to perform 10-15 contactless transactions. Once the phone battery is fully discharged, it enters into ‘battery power-off threshold,’ where there is no residual power to support NFC functions and Vodafone Wallet no longer functions."

Think of this as being akin to how a starving person's body almost shuts down. It's holding onto to life in an extreme low-power mode, hoping to get a charge (or food) before it dies completely.

What Vodafone Pay is using to make payments is that residual power. That minimal power is just enough to power its NFC controller and SIM card. That is sufficient because the bulk of the transaction's power — the RF field — is powered by the POS and the card reader.

Therefore, it's not true that the transactions can happen if the phone is completely "out of battery life." As a practical matter, though, very few consumers ever have phones that get that drained. That means that for the overwhelming majority of transactions where a phone seems to be dead, these transactions will still work. Well, almost.

There's one more caveat and it's one that may make this low-energy approach of minimal value for other NFC payment offerings.

"Vodafone Wallet users can also switch payment cards between two user-selectable payment modes — manual (where a transaction needs confirmation from the user) and an 'automatic' payment mode. Transactions in ‘battery low mode’ only work if the payment card is set to automatic, as manual mode requires user interaction on the screen," Vodafone said in a statement sent to Computerworld. "So customers can choose between convenience using automatic mode (giving them the same security level of a contactless plastic card) or a higher level of security using manual mode, which provides a security level higher than contactless plastic cards, but requires battery power."

In other words, because the screen and the keyboard won't function in low-power mode, the normal authentication procedures can't happen. No fingerprint scan, no selfie, no confirmation at all. The phone pretty much is reduced to pretending to be a regular contactless payment card. That may be a deal-killer for Apple Pay and Android Pay, but it's an interesting — albeit geeky — differentiator for Vodafone Pay.

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