Snazzy Labs
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- First Name
- Quinn
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- Apr 15, 2022
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- Rivian R1T, Genesis GV80, Coda EV
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The wireless charging pad in the Rivian R1T sucks. Part of the problem is its design. The forum's very own @Sonartech found the specs and internal photos used in certification filings that show an array of 15 small Qi coils stacked on three layers. Contrary to popular belief, more coils doesn't mean faster charging. Coils cannot be pooled together to deliver more energy—only one coil is active per device charging. The purpose of coil arrays is to improve efficiency (reducing power loss by misaligned coils) and ensuring greater potential charging coverage over a large surface area (such is the case with Rivian's design). Clustering coils increases the likelihood that at any position on the charging pad your phone is correctly aligned with at least one coil. That's it.
And while a less-sensitive alignment is nice, problems arise from layering coils. For one, the further layer is physically more distant from your phone’s receiving coil. This results in slower (we’ve measured sub-3W charging in the Rivian) and greater power loss due to heat (these phones get darn toasty—especially when they’re also in the sun). Remember, the coil selected is the one that most properly aligns with your phone’s receiver coil. When this is three layers of coils down, partial obstruction can further decrease efficiency and lower the rate of power transfer. Rivian’s charger has its upper-most top-layer coils on the left side of the pad (LHD driver’s side) and we suggest placing your device here when possible—you’re likely to get a more efficient, faster charge (I’ve found it settles in around 5-6W). Not great, but it works. Kinda. That’s only half the battle with Rivian’s charger…
Have you ever wondered why Qi chargers take a few seconds to start charging? Well, the transmitter coil (Tx) frequently outputs small “search” pulses of energy to determine if there is a receiver coil (Rx) nearby (in the Rivian’s case, about 2-4mm). Once the Tx coil detects the Rx coil, the Tx coil provides a tiny amount of power to the Rx coil so your phone can communicate back its power requirements. This handshake process takes time and only until the handshake is completed can the Tx coil send power to the Rx coil. Rivian seems to have designed a very narrow tolerance of misalignment before charging stops (this is often the case with small coils). When your phone slides on the pad—even a fraction of an inch—charging stops and it needs to re-establish power transfer with another coil by starting the handshake process over. When your phone is constantly sliding on the Rivian charging pad’s slippery surface, you’re likely to experience more signal drops and handshake re-establishment than actual charging.
That’s where this post comes in. Lance from the Facebook Utah Rivian Club has designed a very clever 3D-printable solution that fixes most of the problems with Rivian's charging solution by simply immobilizing your phone's Rx coil. Here's a video of how it works:
I recommend this be printed in PETG, ASA, or (preferably) ABS as it will often find itself in direct sunlight in a hot cabin. It is not suggested to use PLA as such a thermoplastic has a significantly lower glass transition temperature and it's also more brittle. This design excels when your plastic is able to flex a little bit while maintaining the ability to return to its original form factor.
A one-size-fits-all for every phone was not possible, but Lance and I have determined there’s a good 3-5mm of flex when printed in a recommended plastic. On the Thingiverse/Printables download page, there are a lot of different sizes listed. Here's an example:
Rivian_Phone_20mm_Y_and_76mm_wide.stl
The first number (20mm) is the y-axis offset (the distance it places the bottom of your phone from the rearmost part of the charger), and the second number (76mm) is your device's width. If you use your phone without a case, it’ll be easy to Google for device dimensions. This reference guide also has dimensions for most modern phones. If you do use a case, it may be worth utilizing calipers to get your device's total width with a case. Make sure you round down to the nearest size. For example, if your phone is 74mm, don't print the 75mm model—it'll be too wide for your phone. Dependent on your phone's coil placement, you may want to try printing a few of the Y-values for your given phone width. The top-most coil series find themselves centered at around 95mm from the bottom of the Rivian charger—that's where you'll ideally have coil alignment.
The formula for guesstimate coil placement is: Y = 95 - (deviceheight/2)
So, with a 150mm tall and 74mm wide phone, I'd do: Y = 95 - (150/2) = 20mm
That gives me, the part Rivian_Phone_20mm_Y_and_74mm_wide.stl
Of course, this is not a hard-and-fast rule. Coils are not always located directly at your phone's halfway point and the width of the plastic part may not align your coil with the 95mm height coil row. Plastic is cheap so it's worth printing a few different models given your device width to see what charges most reliably/quickest.
If there's enough interest from those that don't have printers, it is possible I can do a mass-production run of these on my small print-farm at cost (material+shipping). Thanks for reading and thanks to Lance for the great design!
Models on Thingiverse: https://www.thingiverse.com/thing:5441861
Models on Printables (coming soon!): https://www.printables.com/model/257772-rivian-phone-wireless-charger-adapter-holder
And while a less-sensitive alignment is nice, problems arise from layering coils. For one, the further layer is physically more distant from your phone’s receiving coil. This results in slower (we’ve measured sub-3W charging in the Rivian) and greater power loss due to heat (these phones get darn toasty—especially when they’re also in the sun). Remember, the coil selected is the one that most properly aligns with your phone’s receiver coil. When this is three layers of coils down, partial obstruction can further decrease efficiency and lower the rate of power transfer. Rivian’s charger has its upper-most top-layer coils on the left side of the pad (LHD driver’s side) and we suggest placing your device here when possible—you’re likely to get a more efficient, faster charge (I’ve found it settles in around 5-6W). Not great, but it works. Kinda. That’s only half the battle with Rivian’s charger…
Have you ever wondered why Qi chargers take a few seconds to start charging? Well, the transmitter coil (Tx) frequently outputs small “search” pulses of energy to determine if there is a receiver coil (Rx) nearby (in the Rivian’s case, about 2-4mm). Once the Tx coil detects the Rx coil, the Tx coil provides a tiny amount of power to the Rx coil so your phone can communicate back its power requirements. This handshake process takes time and only until the handshake is completed can the Tx coil send power to the Rx coil. Rivian seems to have designed a very narrow tolerance of misalignment before charging stops (this is often the case with small coils). When your phone slides on the pad—even a fraction of an inch—charging stops and it needs to re-establish power transfer with another coil by starting the handshake process over. When your phone is constantly sliding on the Rivian charging pad’s slippery surface, you’re likely to experience more signal drops and handshake re-establishment than actual charging.
That’s where this post comes in. Lance from the Facebook Utah Rivian Club has designed a very clever 3D-printable solution that fixes most of the problems with Rivian's charging solution by simply immobilizing your phone's Rx coil. Here's a video of how it works:
I recommend this be printed in PETG, ASA, or (preferably) ABS as it will often find itself in direct sunlight in a hot cabin. It is not suggested to use PLA as such a thermoplastic has a significantly lower glass transition temperature and it's also more brittle. This design excels when your plastic is able to flex a little bit while maintaining the ability to return to its original form factor.
A one-size-fits-all for every phone was not possible, but Lance and I have determined there’s a good 3-5mm of flex when printed in a recommended plastic. On the Thingiverse/Printables download page, there are a lot of different sizes listed. Here's an example:
Rivian_Phone_20mm_Y_and_76mm_wide.stl
The first number (20mm) is the y-axis offset (the distance it places the bottom of your phone from the rearmost part of the charger), and the second number (76mm) is your device's width. If you use your phone without a case, it’ll be easy to Google for device dimensions. This reference guide also has dimensions for most modern phones. If you do use a case, it may be worth utilizing calipers to get your device's total width with a case. Make sure you round down to the nearest size. For example, if your phone is 74mm, don't print the 75mm model—it'll be too wide for your phone. Dependent on your phone's coil placement, you may want to try printing a few of the Y-values for your given phone width. The top-most coil series find themselves centered at around 95mm from the bottom of the Rivian charger—that's where you'll ideally have coil alignment.
The formula for guesstimate coil placement is: Y = 95 - (deviceheight/2)
So, with a 150mm tall and 74mm wide phone, I'd do: Y = 95 - (150/2) = 20mm
That gives me, the part Rivian_Phone_20mm_Y_and_74mm_wide.stl
Of course, this is not a hard-and-fast rule. Coils are not always located directly at your phone's halfway point and the width of the plastic part may not align your coil with the 95mm height coil row. Plastic is cheap so it's worth printing a few different models given your device width to see what charges most reliably/quickest.
If there's enough interest from those that don't have printers, it is possible I can do a mass-production run of these on my small print-farm at cost (material+shipping). Thanks for reading and thanks to Lance for the great design!
Models on Thingiverse: https://www.thingiverse.com/thing:5441861
Models on Printables (coming soon!): https://www.printables.com/model/257772-rivian-phone-wireless-charger-adapter-holder
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I use one of these at home and it seems to do just fine. Is there some reason this wouldn’t work, like easy, peasy?
