A full-feature, open hardware battery pack designed to mount under any Polaroid SX-70 camera in order to enable the usage of i-Type film.
The Poweroid is a battery pack designed to mount to the bottom of folding-style Polaroid SLR cameras, such as the SX-70. In combination with a camera modded for ISO-600 film or an ND-filter, it enables the camera to take the cheaper i-Type film otherwise unusable in vintage cameras. The Poweroid aims to be a sleek yet cheap, easy to use, robust, full-feature battery pack with features such as internal USB-C charging, broad camera compatibility and safety considerations. It is supposed to provide an open alternative to proprietary solutions which are often expensive to buy and/or out of stock entirely. Anyone can build the required hardware, given they have access to the necessary tools and good soldering skills.
- Physical on/off switch: The controls include a power switch and corresponding LED indicator. In the off-position, power to the camera will physically be cut.
- Charge level display: There are four LEDs indicating the battery charge, making it easy to tell when the camera is running out of charge.
- Gauge button: There is an additional button which can be used to illuminate the charge level display without powering the camera.
- USB-C charging: The camera can be charged using any common USB-C charger. This includes "smart" chargers such as ones used for Laptops, which require voltage negotiation.
- Battery safety: The internal batteries are protected against undervoltage, overvoltage, short-circuits and physically fused for electrical failure.
- Modular batteries: As the circuit takes lithium cells in parallel, you can use any variant and any number of lithium cells you have available, as long as they are 3.7 V and fit in the case. There are 4 connectors available, more can easily be connected by soldering.
- External voltage protection: The circuit is protected against externally applied voltages. This means you can use 600 or SX-70 film in the camera while also having the Poweroid installed.
- Tripod socket: The device has a built-in tripod socket. This does not require the camera itself to have one!
The Poweroid is theoretically compatible with any folding Polaroid SLR there is, such as all SX-70 models and the SLR680/690, though it has only been tested on SX-70 Alpha cameras so far. Your mileage may vary, especially with Sonar or SLR680/690 models, as their autofocus and/or flash hardware makes them significantly more power-hungry. Unlike with other power packs, the camera does not have to feature a tripod socket, and does not have to be modified internally.
The Poweroid is designed to enable you to use i-Type film, which is lacking an internal battery and is thus the cheapest film type available. While using the Poweroid, you may also use 600 or SX-70 film which has internal batteries. The Poweroid will protect itself from external voltages. Please note that if your camera has not been converted to take 600 film, you will have to use a ND-filter when shooting 600 or i-Type. This will only give you the benefit of cheaper film, though you will entirely miss out on the advantage of the faster film speed. Therefore, it is highly recommended to have your camera 600 converted, or feature-upgraded to new internal PCBs like SX70-R or openSX70.
Keeping safety aspects in mind, you can also use the Poweroid to shoot expired film packs with batteries that have run flat. It is highly recommended to tape off the battery contacts on the film pack before inserting it! Film pack batteries are not meant to be recharged. Doing so may damage the battery (which isn't a problem since it's already dead), it could however also cause it to heat up, bloat, short out, or in the worst case catch fire, if left exposed to external voltage for too long. The Poweroid will essentially try to charge it whenever power is supplied to the camera, so be careful when doing this. The issue can be avoided entirely by putting tape over the battery contacts on the film pack before loading it into the camera, so its internal battery won't be connected to the Poweroid or the camera at all.
The case is designed to be 3D-printed, and can thus be fabricated in any colour filament one may desire. For example, black filament would make sense for black body cameras, white filament for ivory white models. There could also be a modified case design made for CNC milling in order to make it out of aluminum, which may look great on chrome body cameras.
The case is designed to have standard-size Polaroid leather applied to it on the bottom, though it needs a signle straight cut on one side to make it shorter (and some corner rounding). This is the only modification necessary, the tripod mount hole will align correctly, if your leather has one. You do not need to remove the leather from your camera in order to use the Poweroid. If there is no leather on your camera, you can use a 3D-printed insert as a replacement. If you are restoring the leather anyway, you can also cut your new bottom leather piece into two pieces, use the large piece for the Poweroid lid, and the small piece for the area left exposed by the device. For this use case, there is a short version of the 3D-printed insert, which leaves room for the smaller leather piece directly on the camera body.
In order for the Poweroid to be mounted to the camera, the bottom leather needs to either be removed or have holes cut out for the four screws of the body and the two battery contacts. Afterwards, you will need to remove the four case screws previously exposed beneath the leather. Depending on your camera, this will likely require a proprietary 1 mm x 1 mm Robertson screwdriver which is unfortunately very difficult to obtain. One UK-based manufacturer I know of is Polar Bear Camera, though it's quite pricy. The cheap but very tedious alternative would be to file down a different bit into the desired square shape. Once the screws are out, you can slot the Poweroid into place and screw it into the camera using new, longer screws in place of the original ones. If your camera does not have leather on it, you will need to use a 3D-printed leather insert as a spacer between the Poweroid and the camera body. Once you've screwed the housing to the camera, you can screw the lid onto the Poweroid and apply leather, if you have any.
Sliding the power switch to the right will enable the device, illuminate the battery charge display and power the camera. Sliding it to the left cuts power to the camera, the device will go to sleep shortly after. The camera has power whenever the round blue LED is lit up. While the device is off, you can press the little button in order to check the charge display. The device can be charged using any common USB-C charger. While charging, the battery charge display will show you the charging progress. The Poweroid is fully charged when all four LEDs are on. Charging is indicated by blinking. Charge the Poweroid once the charge level is in the red.
This section is to explain how to build a Poweroid battery pack from scratch. It is recommended to use resources from the latest version in the production folder.
In order to build a Poweroid battery pack, you need to have access to soldering equipment, including a hot air station, and a 3D printer. You also need to be reasonably comfortable with SMD soldering. Most generic components use the 0603 package, though there are a couple of smaller components.
The gerber and drill files for the PCB are provided as a ZIP folder (or you may export your own). This ZIP can be uploaded to a PCB prototype manufacturer of your choice. I'd presonally recommend using JLCPCB. Most settings do not need to be changed. Make sure the PCB thickness is set 1.6 mm (standard). You will likely have to buy a minimum quantity of 5. The PCBs should only cost a few dollars.
A list of all components required to populate the PCB ("BOM", bill of materials) is readily provided as a CSV and a human-readable HTML.
It is recommended to source everything from LCSC, a sister company of JLC, however you're free to source the components from wherever using the part numbers (MPN) provided in the BOM.
If you use LCSC, you can import the CSV file and filter by the JLC_PN column. These are the individual part numbers JLC and LCSC use. This will make it easy to find and order all parts. Make sure you order two Pogo Pins and not just one.
Incase you don't want to assemble the PCB yourself, you can also have JLC do it (PCBA), though this is quite expensive, especially for small quantities and thus not recommended.
The case consists of 3 required and 2 optional parts. The Base and BasePlate make the main housing together, closed by the Lid.
Depending on whether you have leather, half leather or no leather on your camera, you may need one of the LeatherInsert variants.
All 3D objects are provided as .stl files. Process them with a slicer of your choice and print them with whatever filament you'd like.
I've found PLA to work very well. If you have the choice, use a flat, untextured print bed.
The batteries inside the device are all wired up in parallel, thus, you may use any variant and any number of lithium cells you have available, as long as they are the 3.7 V type and fit in the case. There are 4 connectors on the PCB, but you may solder on as many more cells as you need. It is recommended to reach a total capacity of over 3000 mAh, getting closer to 4000 mAh is best. The higher you can get the capacity, the better, as the device will continue to operate even at lower voltages and the voltage will deplete more slowly overall, giving you better battery life. When assembling the device, try to make the battery cables as short as possible! Cables that are too long and thin cause significant voltage drop and may cause bad battery life and/or unreliability.
There is a series of LiPo battery cells in the "pouch" style that are named after their dimensions. A cell named 102050 for example would be 10 mm thick, 20 mm wide and 50 mm long. We're specifically looking for types that start with 10, as the case is 10 mm tall and will therefore perfectly fit these. I have personally used 102050 cells, as three of them will fit perfectly into the case, but you really may use anything. Try to get them in the biggest capacity for the size, sometime it varies. While it is highly recommended to buy the cells new, they don't have to be. My prototype camera for example had been running on cells harvested from disposable vapes for years. As the Poweroid has integrated undervoltage and overcurrent protection, the batteries don't necessarily need any such logic built-in. If you want to make the most of the space available, the following sub-chapter should aid you in choosing suitable batteries.
Here's a list of some commonly available battery types:
| Battery | Typ. capacity (mAh) | A | B | C |
|---|---|---|---|---|
| 102050 | 1,000 | ✔️ | ✔️ | ✔️ |
| 102540 | 1,100 | ✔️ | ✔️ | ✔️ |
| 102550 | 1,000 - 1,500 | ✔️ | ✔️ | ✔️ |
| 103048 | 1,500 | ✔️ | ❌ | ❌ |
This list is not comprehensive - it's just some suggestions of what to look for.
In addition to the case and PCB, you will need the following components:
- Any 3.7 V LiPo batteries. Recommended:
3x102050 type cells: AliExpress - Battery cables (others may also work, or they may be omitted by soldering directly to the PCB): LCSC
1xTripod screw adapter: AliExpress8xM3 threaded insert nuts (3 mm length, ~4.2 mm diameter): AliExpress4xM2 x 8 mm cylinder screws: Gedex (50x), OnlineSchrauben4xM3 x 4 mm cylinder screws: Gedex (50x), OnlineSchrauben4xM3 x 6 mm countersunk screws: Gedex (50x), OnlineSchrauben
Source these parts from wherever it is most convenient for you. The provided links are merely examples.
Once you have a finished (and optimally tested) PCB, you will need to prepare the case. If you want a tripod mount, you should install the insert for it first.
The tolerance is very low to make it a press fit. Press it in, make sure it goes in all the way and align the slots so they lign up with the notches on the lid. It's recommended to put some epoxy on the outer threads in order to secure it further.
Afterwards, you need to smelt 8 threaded inserts into the case. 4 to secure the PCB, and 4 for the lid screws. The four inserts for the PCB will hold the Base and BasePlate together to form one piece.
Once the case is prepared, slot the PCB into place and screw it down into the case using the cylinder head M3x4 screws.
Now, adding the leather insert if required, align the case with the bottom of the camera, and screw in the four longer M2x8 screws in order to secure it to the camera.
Note that M2 screws are not quite the right size and will take some force to screw in the first time. Be very careful, turn them back and forth regularly until you're through. Ensure the screws don't stick out into the film chamber.
Finally, screw on the lid using the four countersunk screws, and cover it with leather if you desire.
- Battery life: Despite the new TPS61288 boost IC being quite efficient, the large power spikes of the motor still significantly limit battery life. The MOSFETs in the main power rail are likely to be the main culprits. Choosing better ones may improve performance in the future. Still, the current capacity should be more than enough to run the camera for dozens of packs on a single charge.
- M2 mounting screws: It is currently recommended to use M2x8 screws in order to attach the Poweroid to the camera. Unfortunately, while very similar, they seem to have a slightly different thread from the originals. So far I could not figure out what thread the originals have. If you happen to know, please share your wisdom! When using M2 screws, you will have difficulties screwing them in for the first time. Be careful and turn them back and forth a few times. Once you've screwed them in all the way the first time, they will feel fine afterwards. You will have made the tread slightly larger, though the original screws will still work just fine.
For the time being, the project is licensed under CC BY-NC 4.0, limiting commercial use. If you would like to use this project commercially, please contact me at prismarymail@gmail.com. The commercial restriction explicitly does not extend to camera refurbishment service providers merely using the device as part of their services. Commercial restrictions may be lifted altogether in the future.
