Saving the planet one rechargeable product at a time
Apple Magic Keyboard
Being a product designer for consumer products has caused me to become more aware of our responsibility to help build sustainable products. As my colleagues know, I loathe designing products that rely on throw-away batteries and I will vehemently try to influence clients to use rechargeables instead.
A few years ago, a generous colleague of mine gifted me a 1st generation Apple TV and a Magic Keyboard to go along with it. Since then, my wife and I have enjoyed our Apple TV, and now more so during this pandemic season as we binge-watch everything we can get our hands on. With the increasing demand to search Hulu, Netflix, and Disney Plus, recently she’s been driving me crazing using the Apple remote to navigate the alpha-numeric search menu one letter at a time. The “plop, plop, plop” over 20 minutes of texting on a 90’s flip phone interface is enough to drive anyone crazy! Enter the Magic Keyboard.
For a few years, it has sat idle in the coffee table drawer after soon discovering that it has a fatal flaw - its battery life is dismal. I don’t know if it’s a design flaw or something wrong with my particular unit, but I swear to you that if I put a fresh set of alkalines in it, and use it only two to three times over a month, it goes dead! I love its design but every time I reach for it to search YouTube, its DOA. After some research, it turns out that I’m not alone. The web reveals that others have had the exact same problem with this Apple product.
So because I could not stand to part with the design, to spite its one flaw and need to find a solution to the unbearable hunt n' peck UI of our Apple TV, I conjured up an idea; why not make the Magic Keyboard rechargeable. It turns out, with a little ingenuity, a 3D printer, and some spare and purchased parts it could be possible and retain its beautiful design.
Armed with my frustration, the idea first crossed my mind when I was searching Adafruit’s website and came across a 5V inductive charging kit. This kit is made up of two parts, a transmitter consisting of a copper winding a small circuit board that you power with a 5V supply. The second part, the receiver, is a similar copper winding an attached circuit board to regulate the current that is transmitted wirelessly from the first module.
This product looked ideal for creating a charging base and attached “lump” to the bottom side of my Magic Keyboard. The kit purports that if you place the two coils within 7 to 10mm, you can transfer up to 100ma of current at 5 volts.
First using SolidWorks, I created some 3D CAD to make sure everything would fit. Once I had a design I set out to tackle a few other challenges I had facing me. Foremost, was that I needed to find a way to replace the 3 AA cells with rechargeable cells. Unfortunately, it is not possible to just replace 3 Alakine cells with 3 NiCad cells since Nicad cells produce 1.2 volts each versus the 1.5 volts of Alkalines. In short, I would only have 3.6 volts and would fall short of the 4.5 volts to operate the keyboard, its microcontroller and Bluetooth circuitry.
Fortunately, there was a solution to this too. It turns out that Nicads are produced in a more rare 2/3 form factor (six tenths the length of a normal AA cell).
If I were to replace the three Alkalines with four 2/3rd Nicads I would be able to produce a total system voltage of 4.8 volts – close enough to have the keyboard work sufficiently since most microcontrollers work on 3.3 or 5V circuits.
With a 30mm “dummy” cell that I turned on my lathe and fitted with a cut down 4 penny nail through its center plus the four 2/3rds Nicads I have the length of three Alkalines. Problem solved! Of course “you don’t get something for nothing” – the four Nicads capacity in amp-hours are much less than the Alkalines, but since the keyboard would be spending most of it time in its base recharging, this wouldn't be an issue.
After watching a tear-down video of the Magic Keyboard, I studied how I could interface my charging lump to the bottom side with minimal physical alteration of the keyboard. After producing my 3D print for the charging base and the attaching lump, I then had to do some experimentation with the distance between the two inductive coils. You see, if they happened to be too close together, the NiCad cells would be introduced to too much current. The standard practice for charging NiCads states that its charging voltage shouldn’t exceed approximately 10% of the cell’s capacity.
The cells I purchased off of Amazon are rated at 800ma so that means my target charging current would need to not exceed 80ma. Fortunately, I had designed the base so that the coil could be off-centered from the receiving coil and by adjusting it’s offset, I could decrease its efficiency from 100ma down to 75ma.
With these design issues solved, it was just a matter of wiring the inductive lump to the keyboard and intersecting the Magic Keyboard’s battery connector and tieing into it with wires coming from the inductive receiver.
It turns out the only alternation I need to make to the Magic keyboard was to file a small slot on the removable plastic left foot piece so that I could run my wires to the keyboard’s battery cable.
To my amazement, everything worked out (most of my design projects are not so fortunate). The Keyboard sits on our entertainment center with it’s based plugged into a 5VDC wall brick. I’m very pleased with the result and even more pleased that we can now surf Apple TV without the annoying disappointment of a dead keyboard.
