'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 10

Popular Stories

iPhone 17 Pro Dark Blue and Orange

iPhone 17 Pro to Start at $1,049 With Doubled Base Storage

Wednesday August 13, 2025 1:45 am PDT by
Apple's upcoming iPhone 17 Pro will have a starting price that is $50 more than the iPhone 16 Pro but it will come with a minimum 256GB of storage, doubling the base capacity compared to last year's model. The information comes from Chinese leaker Instant Digital, posting on Weibo. The account, which has 1.5 million followers, has now made the claim three separate times in recent weeks....
ios 26 liquid glass lock screen beta 6

Apple Changes Liquid Glass Again in iOS 26 Beta 6

Monday August 11, 2025 12:09 pm PDT by
Apple is continuing to tweak the way that the Liquid Glass design looks ahead of the iOS 26 launch, and the latest beta makes a change to the Lock Screen. The Lock Screen clock has been updated with additional transparency, allowing more of the background to peek through. Beta 6 on left, beta 5 on right The clock also has more of a 3D, floating look, which is in line with the rest of the ...
Golden Apple Logo

Every Apple Secret That Leaked Yesterday

Thursday August 14, 2025 4:13 am PDT by
Apple made a major slip Wednesday when it accidentally included hardware identifiers in software code linking to numerous unannounced products. The leaked information provided MacRumors with concrete evidence of Apple's hardware development across multiple product categories. Here's everything that was confirmed through the code discoveries: New HomePod mini with updated chip – New...
iPhone 17 Pro Feature Dual

When Will Apple Announce the iPhone 17 Event?

Tuesday August 12, 2025 12:46 pm PDT by
It is now mid-August, meaning that Apple's annual iPhone event is just around the corner. This year, Apple is expected to unveil the iPhone 17, the all-new iPhone 17 Air, the iPhone 17 Pro, and the iPhone 17 Pro Max. Here are some of the key rumors for those devices:iPhone 17: Same design as iPhone 16, but with an A19 chip, a larger 6.3-inch display, an upgraded 24-megapixel front camera, ...
maxresdefault

Top 5 Features Coming to the Apple Watch Ultra 3

Tuesday August 12, 2025 11:48 am PDT by
We're just about a month away from Apple's annual September event, and we're going to get a new version of the Apple Watch Ultra for the first time since 2023. There are some useful new features rumored for the Apple Watch Ultra 3, which we've summarized below. Subscribe to the MacRumors YouTube channel for more videos. Satellite Connectivity - The Apple Watch Ultra 3 will be the first...
iPhone 17 Pro 3 4ths Perspective Aluminum Camera Module 1

Alleged iPhone 17 Pro Chassis Offers First Look at All-Aluminum Body

Thursday August 14, 2025 3:40 am PDT by
An alleged iPhone 17 Pro production leak may provide a first look at the device's milled all-aluminum chassis, which this year includes the camera bump – in contrast to last year's iPhone 16 Pro model that features a glass camera module attached to an all-glass back panel. Originally shared by leaker Majin Bu, the image below could be of a moulding, but it still lines up with rumors that...
Apple TV 2025 Thumb 2

New Apple TV Coming Later This Year With A17 Pro Chip

Wednesday August 13, 2025 5:29 pm PDT by
Rumors suggest that Apple is working on an updated version of the Apple TV that's slated for launch later this year. Information about the upcoming device that was found in Apple code indicates that it will be equipped with the A17 Pro chip. There have been multiple rumors about a new Apple TV coming in 2025 with a new A-series processor, but it hasn't been clear which chip Apple would use...
Tim Cook Apple Park

Apple Launching These 10+ New Products Later This Year

Tuesday August 12, 2025 11:08 am PDT by
While the summer months are often relatively quiet for Apple, the company still has many new products coming later this year. Below, we have outlined at least 10 new Apple products that are expected to launch later this year, along with key rumored features for each. This article was originally published last month, and it has been updated with the latest rumors. iPhone 17 Series iPhon...

Top Rated Comments

DannyT2011 Avatar
134 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)
elmateo487 Avatar
134 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)
Jandmtv Avatar
134 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
134 months ago
Apple covered that port for a reason. Good luck with that strap in the rain.
Score: 6 Votes (Like | Disagree)
dannys1 Avatar
134 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
134 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)