'Reserve Strap' Debuts New Design Focusing on Apple Watch Diagnostic Port - MacRumors
Skip to Content

'Reserve Strap' Debuts New Design Focusing on Apple Watch Diagnostic Port

Originally announced by third-party developers Lane Musgrave and John Arrow back in early March, one of the biggest concerns of the battery-boosting accessory "Reserve Strap" was its use of the Apple Watch's heart rate sensor as a way to provide power to the wearable. Although it was unconfirmed, there was always a possibility of the Reserve Strap obstructing normal functions of the heart rate sensor, or causing the Watch to not function altogether by interfering with skin contact completely.

Last week, after getting their hands on an Apple Watch, Musgrave and Arrow have gone back to the drawing board on the design of the Reserve Strap, coming up with a new look that acts as more of a traditional Apple-made band without blocking the heart rate sensor at all. The new Reserve Strap aims to use the 6-pin diagnostic port - hidden inside of the band port on the bottom of the Watch - as the main source of providing power to the device, shirking the heart rate sensor's magnetic inductive charging altogether.

reserve strap change

The Original Reserve Strap design (left) vs the new design (right)

Finally getting our hands on the Apple Watch has further confirmed the immense value of the Reserve Strap. Since release day, we've been executing series of tests on the Apple Watch and have some really exciting news to share today.

We've developed and tested a completely rethought design that takes advantage of the 6-pin port underneath the band slide of the Apple Watch. This port hadn't been deciphered by anyone until now but we've been able to make significant enough observations so far to warrant shifting our development focus to this new method. We're looking forward to sharing more design details and technical specification of this new Reserve Strap as soon as we can.

The company claims in its blog posts that its engineers have "been able to independently confirm that the 6-pin diagnostic port underneath the Apple Watch case can be used for charging." They continue by also noting the diagnostic port will allow for not only a higher charge capacity, but faster, more efficient charging times. The blog post also notes that the new method should improve durability of the strap as a whole and eliminate "any interference with Apple Watch functionality including taptic feedback and heartrate sensors."

reserve strap port sketch

Initial renderings of the new design (left) vs fully realized 3D model (right)

No word was given on the planned Kickstarter for the Reserve Strap, but those interested can still pre-order the device from the company's official website for $249.99. Color options will include white, gray and black, and customers will be able to choose between 38mm and 42mm strap sizes to fit their preferred Apple Watch size.

Related Roundup: Apple Watch 11

Popular Stories

watchos 27

watchOS 27 Is Wiping Four Apps From Your Apple Watch

Monday June 22, 2026 8:17 am PDT by
Apple's watchOS 27, previewed at this month's WWDC, removes four built-in apps from all supported Apple Watch models, folding three of them into a single Find My app and dropping Walkie-Talkie entirely, based on the first developer beta released this month. The largest change affects Find My. watchOS 27 developer beta 1 replaces the separate Find Devices, Find People, and Find Items apps...
apple world surf league video

Apple Shares Video on How Pro Surfers Use Apple Watch During Competition

Tuesday June 23, 2026 9:57 am PDT by
Apple today shared a video showing off the Apple Watch in use at the World Surf League Championship Tour, with surfers describing how they use the watch when competing. Surfers can be hundreds of meters away from the beach during competitions and can't hear announcements over the sound of the water and the wind. The World Surf League has adopted the Apple Watch to solve the problem, linking...
series 10 apple watch titanium digital crown

Report: Apple Watch Redesign Coming Next Year With New Band System

Tuesday June 30, 2026 8:45 am PDT by
A "major overhaul" of the Apple Watch's design is due to arrive next year with a new system for connecting bands, according to a known Weibo leaker. In a set of recent posts, the leaker known as "Instant Digital" linked the new claim to older rumors about an "Apple Watch X" model, which was said to introduce a fresh design and break compatibility with the existing watch band system. Citing...

Top Rated Comments

DannyT2011 Avatar
146 months ago
It won't work. Look at the connector. Those of us who have our watches already know that the way to attach a strap is to slide it in. Straps won't slide with a big connector sticking out of them.

It looks like there are buttons on either side of the strap that you would pinch to insert/release. Perhaps as you pinch them, the connector will retract and then will connect to the port when you release them?
Score: 13 Votes (Like | Disagree)
146 months ago
It won't work. Look at the connector. Those of us who have our watches already know that the way to attach a strap is to slide it in. Straps won't slide with a big connector sticking out of them.

Lol. This made me laugh. They have engineers who can extract info from a diagnostic post... Yet you think they didn't think of that? Especially since they have one in their hands now.
Score: 6 Votes (Like | Disagree)
146 months ago
Apple covered that port for a reason. Good luck with that strap in the rain.

Yup, only to include it as a new feature with the watch2.
Score: 6 Votes (Like | Disagree)
shareef777 Avatar
146 months ago
Apple covered that port for a reason. Good luck with that strap in the rain.
Score: 6 Votes (Like | Disagree)
dannys1 Avatar
146 months ago
I take it these people are aware that having batteries in a watch band is something Apple has patented.

Which begs the question, why didn't they launch with battery bands?
Score: 6 Votes (Like | Disagree)
shareef777 Avatar
146 months ago
We all know the watch needs the iPhone to operate, and the iPhone doesn't last more then 18 hours so why does the watch need to? If you have to recharge your iPhone every night, it should be easy enough to charge the watch as well.
Score: 5 Votes (Like | Disagree)