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LiFePO4wered/Pi+

Next Gen LiFePO4 battery / UPS / power manager for Raspberry Pi, ideal for headless and IoT use

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Many IoT and other projects are based on the Raspberry Pi, but usually little thought is given to the power supply. Most project use generic cell phone adapters or USB power banks, which is fine for one-off projects where the duct taped parts and cabling don't matter and it's expected that SD cards will die because power was removed with the Pi running.

But when you need reliable non-stop operation for your prototypes, or you're ready to turn your project into a good looking product, or you want to use different power sources such as solar, it's time to look for a serious power manager for your Pi.

Built on the solid foundation of the #LiFePO4wered/Pi, this project provides Pi bootup and shutdown management based on button or touch, input voltage, battery voltage and time, all while making sure the Pi always performs a clean shutdown before power is removed.
In addition it provides significantly higher power, RTC functionality and Pi current measurement.

It was a hard decision to start from scratch with a new project for this next gen effort since the #LiFePO4wered/Pi project has such good traction and a gazillion likes, but the more I thought about it, the more I realized that starting with a clean slate would allow me the freedom to make this what people want it to be instead of feeling shackled by legacy, and at the same time prevent confusion about the different generations. A new project also allows me to enter it for the 2017 Hackaday Prize. :)

There are some issues with the current #LiFePO4wered/Pi design that I hope to address in this Next Gen effort:

1. Make it easier to assemble. The two-PCB arrangement with the charger on the bottom and power manager on top makes for a nice and compact unit, but it takes too much time to assemble. The original design sprang from a desire to provide an example application for the #LiFePO4wered/USB, but the #LiFePO4wered/Pi has turned out to be a much more popular product in its own right. So this will be a single-board setup with the charger and power manager both on one PCB, significantly reducing assembly time and cost. It is the best way to reduce cost and support higher volume.

2. Alleviate power limitations due to physical size. Power supplies unfortunately generate quadratically more waste heat as the current goes up (P = I^2 * R), and the tiny PCBs in the current design have a hard time sinking this heat away. Customers always want more power, but recent experiments with higher power on the current physical design have convinced me that the only way to allow more power is a bigger PCB with more copper.

3. Improve hackability. For a product targeted at hardware hackers, the current design is not the most hacker friendly, mostly because there is very little room due to the small size. Customers want to connect different power sources, have the on/off button and LED remotely located, etc. The current design has some tiny surface mount pads to allow such things, but decent sized through-hole pads and more configuration and customization options would definitely be welcome.

4. Make load current independent of charge current. Some people don't need a big battery for long untethered run time, they just want a little bit of juice, enough to shut the system down safely when external power fails. But in the current design, maximum UPS load current is linked with charge current, which in turn dictates battery size. I hope to separate these two concerns and provide high load current with a small battery as well.

5. Improve physical stability. This isn't usually a problem, but the current mounting method with one screw and the weight of the battery supported on the 4-pin connector between the boards is not ideal. I plan to use a 40-pin header and connect to at least 2 screw holes.

So here is my current plan to make this happen:

  • Start with a Pi Zero-sized PCB, extended past the GPIO header so the battery can still sit next to the Pi, but upside-down. Have one PCB design that can accommodate both the 14500 and 18650 cells. The 18650 will be located more forward than in the current design, making sure it doesn't stick out farther than the USB ports on a Model B+ any more.
  • The circuitry will be over the Raspberry Pi as is the case for most HATs. The components will be mounted on the bottom of the PCB, with only the on/off button (mechanical switch) and LEDs mounted on top. Most of the top of the PCB will be copper plane for heat sinking, on which an additional heat sink can be mounted if deemed necessary for high power applications.
  • There will be through holes for remote on/off button and LEDs, to easily connect input power other than USB, give access to 3.2V battery power and switched 5V output power, connect external LiFePO4 cells and loads, and adjust the charger's MPP for use with solar panels.

Anything I've missed? Comments and requests are not only welcome but highly encouraged!

LiFePO4wered-Business-Pitch.pdf

Buniness Plan/Pitch for Hackaday Prize Best Product

Adobe Portable Document Format - 308.92 kB - 07/21/2017 at 19:20

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sheet - 10.73 kB - 07/18/2017 at 21:06

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LiFePO4wered-PiPlus-CC-BY-SA.pdf

LiFePO4wered/Pi+ schematic as of 6/12/2017, CC-BY-SA licensed

Adobe Portable Document Format - 45.87 kB - 06/22/2017 at 19:38

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  • 1 × CN3801 Power Management ICs / Switching Regulators and Controllers
  • 1 × TPS61236P Boost converter with bidirectional load switch
  • 1 × MSP430G2232 Microprocessors, Microcontrollers, DSPs / ARM, RISC-Based Microcontrollers
  • 1 × SSM3J332R Discrete Semiconductors / Diode-Transistor Modules
  • 1 × DMG2305UX Discrete Semiconductors / Power Transistors and MOSFETs

View all 10 components

  • Current sense bypass check

    Patrick Van Oosterwijck08/16/2017 at 22:42 0 comments

    One concern I had was that when using the small 14500 size battery, the current sense resistor that limits the charge current also is in series with the load when running from the battery.  My concern was that it would drop so much voltage that the software would decide that the battery was depleted and shut down.  This is, of course, not a problem since the battery voltage is measured directly at the battery, and not after the sense resistor.  But I had temporarily forgotten that. :)

    So I did a test where I used a MOSFET to bypass the 0.18 ohm resistor when the input (charge) voltage was not present.  I wanted to see if it affected run time from the small battery.  This is still a valid test, because the boost converter does see lower input voltage due to the voltage drop across the sense resistor, so its efficiency might go down.

    The test was done with a Pi3 with 4 cores @ 100% and an active SSH connection over WiFi.  Here are graphs of the battery voltage in mV:

    Oddly, the results look better without the bypass.  The worst result was after a recharge a day ago, the voltage would droop and threaten to fall below the shutdown threshold, but then recovered.  The longest run time is without any bypass, and was about 23 minutes.

    I don't know for sure what caused the initial droop, it could be a chemical effect in the battery when charging wasn't recent and ion mobility may be lower.  I will have to do a little more testing on that since it comes dangerously close to the shutdown threshold.

    Overall this is good, the little battery did hold up so it's promising as a solution for those who are looking for UPS functionality and just want enough power to get through a clean shutdown.  The Pi was pulling ~950mA at 5V, which translates to about 1.6A at the battery voltage.  Testing with my electronic load seems to indicate 1.2A output current is the limit for the small cell, at which point the boost converter output droops to ~4.85V, still within the USB spec.

  • Getting to 2A... or not

    Patrick Van Oosterwijck08/10/2017 at 23:43 1 comment

      In trying to get to my goal of 2A output power, I've run into my old nemesis again: heat.  After getting stable operation at 1.8A continuous output current, I thought I could get to 2A with minimal effort just by changing some current sense resistors.  But this doesn't seem to be the case.

      The main culprit is the asynchronous charger's Schottky diode.  For all other power components, it's pretty much up to me how much heat they generate.  If it gets too hot, just get a MOSFET with lower RdsON, or an inductor with lower resistance etc.  But for the Schottky diode, it's another story.  Sure, you can get a diode in a larger package, allowing it to dissipate more power safely, but it's still going to generate the same amount of heat, because due to physics the diode will always drop voltage.  So it will always dissipate power (P=V*I).  Worse, the amount of voltage it drops goes up with higher current as well.

      Now 2A doesn't seem to be that much current, but keep in mind that I'm aiming for 2A output current at 5V, which means that with a battery voltage of minimum 3V, and counting on converter efficiency around 85%, the diode sees average currents of (2A*5V)/(3V*0.85)=3.9A.  Now I understand why, even though the power components are external, the CN3801 datasheet indicates 4A maximum output current.  How much power is dissipated?  At 4A, the SS56 Schottky diode I use drops around 0.6V, burning off 2.4W.  As it gets hot, it starts to exhibit an appreciable reverse current as well, leading to even more losses.

      The mechanism preventing me from getting to 2A due to this heat seems to work like this: as the circuit (mostly the diode) heats up, some of this heat warms up the CN3801, eventually at high temperatures making the current sense voltage reference drop.  Nominally 120mV, I've seen it go as low as 95mV when drawing high currents.  This will in turn limit the amount of current drawn (for the same sense resistor, lower current will generate this lower sense voltage).  So the whole thing is self-limiting: as it gets hot, it will limit the current.  This could be considered a feature I guess, but the bottom line is that even when you lower the sense resistor, as things get hot the sense voltage drops enough to negate the lower sense resistor.

      I've been considering possible solutions and what this means for the project:

      1. Is there a way to turn this into a synchronous converter (replace Schottky diode by MOSFET) with some clever circuitry and if so, how much circuitry and will it fit?  The chip has no complementary output for this so it will have to be a hack.
      2. My simple topology of running all current through the charger is showing its limits.  Another topology would be to only run the charge current through the charger and provide a parallel path for the load current directly from the power input.  Downside is that now the 5V converter needs to become step-up/step-down, since the input voltage can be as high as 24V and the battery voltage as low as 3V and both need to convert to 5V.  A step-up/step-down immediately pushes you into chips that are in the several-dollar range.
      3. A spec fix: instead of 2A max, advertise the system as 1.8A max.  The heat still bugs me, and will limit the current even lower at higher temperature.  2A is also a nicer number, and what the Raspberry Pi foundation recommends for a Pi3 power supply.  On the other hand, 1.8A is double what the current #LiFePO4wered/Pi3 can do without active cooling, so it's still a pretty nice upgrade.

      I would very much like user feedback on this.  How much current do you need?  The current design works well at 1.8A, and can probably go into production this fall.  Completely changing the topology will get me past 2A, but is a big redesign that will likely not reach production this year.  Would it be worth...

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  • Load test results

    Patrick Van Oosterwijck06/22/2017 at 23:40 1 comment

    Finally got around to doing some serious testing, and overall the results are looking good!

    I used a prototype with the battery holder area broken off and an external battery connected. This configuration has the smallest PCB copper area, and as such will have the worst thermal performance. I tested with a Pi3 @ 100% CPU first to get a baseline. This first thermal shot is running from the battery without charging:

    Very good, doesn't get hot at all even though the Pi is cooking!

    Now a shot while also charging the battery:

    The hot spot is hotter and has shifted to the charging area, which makes sense. The charger is an asynchronous step-down design, which is less efficient than the synchronous boost converter.

    To be able to see the components (which are on the bottom, facing the Pi), at this point I decided to switch to my electronic load instead. First I ran the system at a load of 1A, similar to a Pi3 at 100% CPU:

    As expected, the culprit is the asynchronous charger's Schottky diode. Unfortunately, the diode will always drop a voltage, so it will always dissipate heat. Because I anticipated this, I put a ton of vias around the diode to try and pull as much of this heat as possible to the top side ground plane. As the images show there's only a few degrees C difference between the diode temperature and the temperature measured on the top side, so this seems to be doing the trick. My prototype PCBs only use 1 oz copper as well, for production I intend to use 2 oz copper instead which should increase the heat sinking capability of the ground plane.

    Next I wanted to see what would happen if I really loaded this puppy. I cranked up the electronic load to 2.5A. I only designed the system for 2A loads, but I like to be mean during testing to make sure things aren't marginal.

    Ouch, hot! Unfortunately the FLIR camera can't seem to measure hotter than 120C, so I don't know how hot the diode actually is. On the plus side, the diode is rated for 150C, and I had it running for several days like this without anything going up in smoke. :)

    The boost converter got pretty hot too at this load:

    As this chip is rated up to 125C, I don't think this is something to worry about at this point. If the system is going to be used at high load and elevated ambient temperature, more thermal management will have to be added. I intend to do some future tests with a heat sink on top of the PCB as well.

    On the low power side, the system is pulling 3-4 uA from the battery with the Pi off, so it seems my scheme to disconnect the charger from the battery when not charging is working as well.

    I tried to run at high load continuously but I ran into an issue with that. I would try to run overnight but would find the system off in the morning. I finally figured out the charging chip was regulating to a lowish 104 mV across the current sense instead of 120 mV. So the system was discharging the battery instead of charging it. I had to lower the load to 1.8A to keep the battery charging. This means that I need to make some adjustments in the current sense resistors to account for tolerances due to temperature etc and still reliably charge the battery at 2A load.

  • It's alive!

    Patrick Van Oosterwijck05/19/2017 at 23:35 0 comments

    After hacking on firmware for the past two weeks, I'm happy to report that the prototypes are working!

    Here are my two protos: running a Pi 3 and a Pi Zero W:

    The prototype in the back uses a 18650 LiFePO4 battery and stackable header, the one in the front uses a 14500 (AA) LiFePO4 battery and normal header. To remove the excess PCB used for the bigger battery from the unit with the smaller battery, I had added perforations to the PCB, but I was worried that the copper foil might peel when breaking it off. I decided to see what would happen with and without scoring with a knife, so I scored only part of the perforated area. Here's the result:

    The section of PCB broke off very clean, and I honestly cannot see any difference between the part that I had scored and the part that I hadn't. Very good news! I'll have to see what happens when breaking off the bigger section when I'm ready to build a prototype with external battery.

    On the firmware side, I worked on the following:

    • Different pin assignments since I had to switch to a 20-pin package to accommodate an extra signal and had run out of pins.
    • The extra signal allows measuring the Raspberry Pi current consumption.
    • Separate single point calibration values for VIN, VBAT, VOUT and IOUT instead of a single calibration value based on VBAT. Since the range of VIN is now huge (24V) compared to the range of VBAT (5V), the single calibration value wasn't working well.
    • Added shadow buffering to the I2C driver. This allows atomic read and write of multi-byte values to prevent race conditions, and will be very important when implementing RTC functionality.
    • Timeouts for boot and shutdown phases. At the moment they are hard coded to 5 minutes for boot and 2 minutes for shutdown, but the idea is that they will be settable in 10 s increments. This improves behavior when the Pi is not present or unresponsive.
    • Support for mechanical switch (default for LiFePO4wered/Pi+) in addition to capacitive touch. As you can see in the pictures, the prototypes have a side-facing switch as well as a top-facing one. The side-facing will likely be standard and the top-facing an option. There are also pads to connect an external button or cap touch pad.
    • Improvements to reduce power consumption when off (still monitoring voltages and button), around 3uA now. Initially I had a problem where the current was ~80uA if the Pi wasn't connected.

    Once functional, I could do some preliminary testing, and things look promising:

    • With a Pi 3 running at 100% on 4 cores (~950 mA), the board was warm but not hot. This is promising for extra power capability!
    • The split sense resistor scheme to allow much higher load current than charge current seems to work! The prototype with the small battery was able to power a Pi 3 @ 100% while also charging the battery quickly, but not above its rating when under low load.
    • The 40-pin header with 2 screws seems to be mechanically solid.

    Next I'll need to do more detailed high-power testing to see where the limits are. I still need to add registers to set the boot and shutdown timeouts and implement RTC functionality.

  • First prototype build

    Patrick Van Oosterwijck05/08/2017 at 23:53 0 comments

    I decided to build up my first prototypes of the LiFePO4wered/Pi+ today. Since I wanted to do all 3 boards I received from OSH Park, and there are quite a lot of components, I figured using solder paste and reflow was the way to go instead of manual soldering.

    I had not ordered a stencil so I used the laser cutter at the Tinkermill to cut my own stencil from plastic film. It never turns out as well as the professional ones you can buy, but it's free and usable. :) Below is a picture of the stencil over a bare PCB:

    Time to apply solder paste:

    The result with the stencil removed is fairly decent, even for the tiny and weird TPS61236P boost converter pads:

    I decided to paste all 3 boards and then build them up in batch:

    The disadvantage of doing this is that the paste tends to dry out during the long build. Placing the components took around 2 hours and the paste was definitely getting dry, but it seems to have had no ill effect. Here are the boards with all components placed except the inductors:

    And here's a closer shot, ready to go into the reflow oven:

    Here's the first board after reflow:

    Looking good! :) Even the TPS61236P connections seem to have soldered fine. I was a little worried because the stencil wasn't exactly accurate for those tiny pads.

    Here are all three boards done:

    I still need to add the LEDs on the other side of the boards, and maybe a top button. As you can see, there is a side-facing button already on the boards but I want to evaluate different options such as side-facing and up-facing. I also need to add the 40-pin GPIO headers and battery holders.

    Then I need to take the existing #LiFePO4wered/Pi firmware package and port it to this new platform. This new design needed more pins than were available on the micro I was using before, so I'm using a different part from the same family and some pin assignments have changed. Plus, I need the firmware to sample a physical button instead of a touch button and use the 32kHz crystal instead of the internal RC oscillator.

  • First prototype layout

    Patrick Van Oosterwijck04/17/2017 at 23:49 0 comments

    My prototype layout is done!

    Some OSH Park renderings below:

    All in all I'm pleased with the result. It was harder than expected to cram it all in, especially the larger (higher current + lower cost) inductors take up a lot of space. This board has the following features:

    • Micro USB or through hole 0.1" connections for VIN. Voltages up to 15V should be supported, making it possible to hopefully power this directly from 12V car power or a <15V Voc solar panel.
    • Footprint for 3 types of tactile buttons, two on top and one side facing. The idea is to evaluate different button options (only one would be populated). There are also 0.1" connections for an external button. The firmware will likely still support capacitive touch for the external button, but not on the PCB itself, and a mechanical button will be the default. This will likely reduce quiescent current as well below the current <4uA.
    • The charge and power LED are right by the micro USB and button, making the user interface nice and concentrated on one side. There are also 0.1" connections to connect external LEDs if desired.
    • MPP voltage is adjustable by adding a resistor to the 0.1" MPP connections. 4.65V by default for USB use, but if you use solar you can customize this now.
    • Switched 5V output to the Pi (hopefully 2A+) is also available on 0.1" connections to drive external load like a screen.
    • The PCB has break-off areas to accommodate either a 14500 (AA) or a 18650 size battery holder, or they can be broken off completely and a battery can be attached to 0.1" connections. Without the battery holder extensions, the PCB is Pi Zero size. The break-off quality is not tested yet and to be evaluated.
    • A solder jumper is available to configure either 0.55A (14500 battery) or 1.5A (18650 battery) charge current. The current sense resistor is split to try and implement the higher-load-than-charge current system described in the previous log.
    • A solder jumper is available to reduce the output voltage from 5V to 4.25V. The Pi and many peripherals can run at lower voltage and it makes the power system (on both the LiFePO4wered/Pi+ and Raspberry Pi) more efficient.
    • An external 0.1" connection for VBAT is available for loads through a 1.5A resettable fuse, but if you use this you need to make sure to manage low battery conditions yourself and draw very little power when the system is off! If loads connected to this are switched from Pi GPIO outputs, it should be fine because they should turn off when the Pi is turned off. But mind the quiescent current, discharging the battery too much will kill it!
    • With the new boost converter it should be possible to measure the 5V load current to the Pi and read it over I2C!
    • Footprints for several types of 32kHz crystal are present, to implement RTC functionality.
    • An EEPROM is present to implement the HAT spec! (Although the physical shape still won't meet the spec.) Hopefully this will result in easier software setup in the future.

  • Experiments on current LiFePO4wered/Pi

    Patrick Van Oosterwijck04/04/2017 at 18:38 0 comments

    Since electrically this project is an offshoot and/or combination of the #LiFePO4wered/Pi and #LiFePO4wered/18650 projects, the current hardware I already have makes a good platform to do experiments on.

    In fact, one of my recent experiments, which now really belongs here more than on the LiFePO4wered/Pi project page, was already documented in this LiFePO4wered/Pi project log. I was testing the TI TPS71235P, a new high power boost converter I intend to use for this project. In fact, now that I will be having enough space for a resistive divider to set the output voltage, I intend to use the TPS71236P instead, which will allow me to configure the output voltage myself instead of using a fixed 5.1V. Since efficiency and current capability get better when there is less difference between the input and output voltage, I want to have a default output of 5V but provide a solder jumper that allows the user to reduce the voltage to 4V for more efficient operation if their system allows it.

    In the current physical form factor of the LiFePO4wered/Pi, the booster was able to support a continuous current of 1.6A at 5.1V, and as this thermal image shows, the inability to shed heat was the limiting factor that made the thermal protection kick in at higher currents:

    The image clearly shows that the heat stays very concentrated in the little PCB. My hope is that with the LiFePO4wered/Pi+ going to a larger PCB with 2 oz copper, this heat can be sinked away from the chip more effectively and I hope to be able to support at least 2A continuous output current.

    Another goal for the LiFePO4wered/Pi+ is to make the maximum load current independent of the charge current. To do this, I intend to split the current sense resistor on the charger and connect the load to the midpoint. By choosing the right resistor values, the charge current can be limited to a safe value for the battery while the load can pull significantly higher current directly from the power source. The principle is demonstrated in the graph below:

    In this case for the 14500 cell, the charge current under no load is about 550 mA, but as the load current increases, the total current pulled from the input goes up to accommodate the load. As the load current gets higher, it takes more and more from the input until eventually at 3A there is no charge current left for the cell and the cell will start to provide current instead.

    You may have noted that I'm designing the charger for 3A instead of the 2A that I mentioned above for the load current. This is because the boost converter trades current for voltage, so that even with ideal components and no losses, a load current of 2A at 5V requires an input current of 3.33A at 3V. So I really should go for a higher current than 3A for the charger, but the test below was done at 3A charge current and has me worried to go any higher:

    The problem is that the charger uses an asynchronous buck design and the Schottky diode always drops around 0.5V at high current, making it dissipate a lot of power. I need to see what temperatures I get on a bigger PCB before I start thinking about pushing the charger current any higher. I may also need to see if I can find a synchronous charger instead, but it's hard to beat the CN3801 I use currently on value.

    Also, the CN3801 is not a low leakage chip, and leaks quite a lot of current from the battery when it's not charging. That's why I currently use a MOSFET to disconnect the battery from the charger when it's not being charged, similar to what can be seen in the #LiFePO4wered/Solar1 schematic (Q4), which reduces the leakage to less than I can measure (<1uA). The problem is that the current topology doesn't work with the split current sense resistor scheme described above. So I need to disconnect the battery differently.

    I did an experiment yesterday with moving the MOSFET up to right after the inductor instead:

    Hackish, but it did the job well enough to test the concept. :) This reduced...

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Discussions

Jay wrote 08/05/2017 at 13:37 point

Any new updates since the initial load test results you posted 06-22? I'm interested in using a Raspberry Pi as a hub for an environmental monitoring device and your design makes my plan for it much more practical. Interested to know how the 2 oz copper works as a heatsink vs the 1 oz from before!

Thanks Patrick!

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x893 wrote 06/16/2017 at 09:19 point

Hi,

possible use TPS61089 ?

I have some problem with download schematic - can you publish info on github ?

Thanks in advance

  Are you sure? yes | no

Patrick Van Oosterwijck wrote 06/22/2017 at 19:41 point

That chip is more expensive than the TPS61236P I'm using, any particular reason for the suggestion?

Looks like the Hackaday.io CDN choked on the "+" in the file name of the schematic, I changed the name and now it seems to work.  Hackaday, fix this so it either works or tells me there's a problem when I upload the file!

Wonder if the "lack of schematic" made any different in the Hackaday Prize judging... :(

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Antoine wrote 06/14/2017 at 08:35 point

Hello Patrick,

I have already purchased your LiFePO4wered-Pi3 ™ from Tindie.
Our prototype is based on Pi Zero W for AQI.
Now I have to select Solar Panels and there is a big gap between the average output panels (Vmpp 12V to 17V) and the LiFePO4wered-Pi3 ™ V.in Max (9V).
As you said, the MPPT is also less relevant for panels.


That's why this new version is very clever.

Our vote goes to You.

We keep in touch from South of France

  Are you sure? yes | no

Stevo wrote 05/29/2017 at 21:36 point

I would like to buy two when your have finished the development. How many amps can it supply to the Pi? I have a bunch of peripherals attached to one of mine. I love the battery backup idea. I have lots of 18650s and one of them would be great to power it in the event of power loss until it can be safely shut down. I have a lot of little nieces that tend to trip over chords, unplug things for the fun of it, and create a general state of complete havoc.

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Patrick Van Oosterwijck wrote 06/22/2017 at 19:43 point

Hello, I'm designing this version to be able to supply 2A to the Pi and whatever you may have connected to it. :)

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Magnus Eriksson wrote 05/27/2017 at 19:22 point

Hi. Patrick Van Oosterwijck
It looks very interesting.
I wonder if I can buy 2 pieces of LiFePO4wered / Pi
Then I'm building a bit of a Rasberry pi 3 type that I'll have in my vehicles
I am also interested in being able to drive them with solar cells.
I'm most interested in the model with 18650 cells.
Sincerely
Magnus Eriksson

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Patrick Van Oosterwijck wrote 05/29/2017 at 18:58 point

Hello Magnus,

You can buy the existing LiFePO4wered/Pi3 on Tindie: https://www.tindie.com/products/xorbit/lifepo4weredpi3/

It will be a while longer before this next gen version will be available since I need to do a lot more testing on it. :)

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doubleodoug wrote 05/26/2017 at 22:21 point

Could you post your schematics? Ideally as pdf. I would really appreciate it.

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Patrick Van Oosterwijck wrote 05/29/2017 at 18:55 point

Planning to post the schematics soon... I just need to overcome my reluctance to give my hard work away. :)

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x893 wrote 05/26/2017 at 19:06 point

Super project !!!

Can you publish schematics for LiFe.../Pi+ ?

  Are you sure? yes | no

denplis wrote 05/11/2017 at 19:53 point

Could it be possible to use a few 18650 cells ?

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Patrick Van Oosterwijck wrote 05/29/2017 at 18:54 point

Yes, several 18650 LiFePO4 cells in parallel is supported, you will be able to connect them to the BAT through hole terminals and break off the existing battery holder if required.

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oshpark wrote 05/09/2017 at 18:45 point

Awesome project!

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SlumberMachine wrote 04/06/2017 at 23:40 point

Looking forward to your progress.  I have 2 of your lifepo4weredpi and they have been working great for me.  They even helped me detect and deal with a bad charger I had received by safely shutting down the pi because the usb charger was giving intermittent power (also started smelling like burnt plastic).  Probably would have cost me some corrupted SD cards if it wasn't for your lifepo4weredpi.  BTW - I'm using it for a time lapse setup which I leave connected to usb battery bank. 

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Patrick Van Oosterwijck wrote 04/30/2017 at 20:56 point

Thanks for the feedback and glad to hear the LiFePO4wered/Pi are working well for you, I always enjoy hearing how people are using them. :)

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