I recently came across a video online where Nick Howe, author of Owning Model S, introduced a device that could potentially increase the USB charging speed of smart devices when used in conjunction with the Model S USB ports. This was certainly intriguing especially having heard that the Model S USB ports were rated at different amperages. The closest USB port to the driver’s seat is rated at 2.1 amps while the port directly next to it – let’s call it the passenger side USB port – is rated at 1 amp.
I, for one, definitely want to maximize the charge rate from the driver’s side port so I decided to pick up the recommended device and put it to the test.
Measuring USB Power
Devices used for the test:
- Model S (production April ’14) with Firmware 6.0
- iPad 4, iPad Mini (original), and an iPhone 6
- Digital USB Volt/Amp meter
- PortaPow Fast Charge USB Adapter (universal)
- 2 USB cables for the Apple devices; one from Apple (standard cable) and one Amazon basics certified clone.
Disclaimer: my test was performed strictly using Apple iOS devices. It’s quite possible that Android based devices may see different results.
Theory Behind “Faster” USB Charging
Without going into excessive detail, smart phones and digital devices that transmit data can only charge as fast as the negotiated USB protocol allows for (USB 1.0 vs 2.0 vs 3.0). The concept behind the PortaPow adapter is that it removes the transmission of data when a smart device is plugged into a USB power thereby making the device receive charge at a much faster rate, and up to the power limits of the port itself.
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USB Charge Results
The row in green represents the USB source where PortaPow was effective in providing a faster charge rate, which to my dismay only occurred when used with my MacPro USB 3.0 port.
Sadly, there were no benefits when pairing the PortaPow with the Tesla Model S USB ports. In fact, the PortaPow accessory actually reduced the charge rate by nearly 6% regardless of whether we used the driver or passenger side USB port.
Summary
I confirmed that both ports on my Model S charge at a rate of 1 amp, and not the 2.1/1 amp that some forum members (myself included) have previously reported. Actual measurements indicate that the PortaPow device is useless in the Model S. Skip it.
My recommendation is to get a good USB car charger that’s capable of charging at the maximum 2.1A rate. You can pick up a decent charger for under $20 that will actually do the job.
