Sub 100 Wh portable power station

Finally completed the demo video as well.

This is the last devlog EVER for this project.

It has been a great experience for me. Everything from the late night strides to the unexpected mistakes to the excitement of thinking about reaching this day..

HOLY, I’m gonna miss Stardance soo much..

Completed most of the editing, planning to finish everything by tomorrow… Soooo sleepy rn………

Had shot videos on my desk for 4 hours today (not lapsed btw), started off with the intro-hook of the video. Need to focus more and make it better tomorrow

Started off with the video editing process. Hopefully I complete it on time. Wish me luck ^.^

Finally completed the assembly.

Not sure how, but reseating the button wires were enough to fix the intermittent button issue.

With this, I can finally declare that the hardware and code part of this project is over.
From tomorrow, I’m planning to do the video editing of the demo video and probably also the social media video.

I am very happy and satisfied with the performance of the power station. Everything works like intended.

Future plans? I’m gonna make another power station with LiFePO4 cells at 768 Wh and a 2000 Watt inverter. I’m not going to use arduino based UI, but rather straight up, manual switches and relay in order to further minimize the footprint.

It is kind of sad to see the end of this project that I felt never-ending and impossible on day 1 :).

Thanks for reading till the end and also following my progress :D.

After a long time, I had managed to do an almost 2 full hour long session today.

Here’s what I did for today:
Successfully reseated the fuse.
Put the inverter board back into its enclosure
Took it out since I forgot to mount the TO220 package components on their metal heatsink.
Put it back into its enclosure.
Noticed that the screw was touching the heatsink, which might cause issues.
Pulled it out again, bent the sheet a little and bent it too much, making virtually no contact with a MOSFET. Took it all out, bent the sheet back, spent another 10 minutes looking for the orientation, and finally secured it very firmly.
Had to be gentle during the assembly and yet I broke a screw peg and did a temporary, caveman plastic welding.
Like always, I was ranting about the repairability of this portable power station in my mind.

Now I’m seeing another issue (not another -_-):
The down arrow button doesn’t work. It worked intermittently for a bit while assembling but now it is completely dysfunctional. Need to diagnose this tomorrow

Tried soldering a new fuse, its still incomplete. Gotta try with my hoof tip tomorrow.

Getting this fuse in pure traffic and 100 other people in the same automotive shop was a bit challenging for me :U.

Since heating power is I²R, the heat scales quadratically up with the flowing current. Hence if our inverter draws, say 30 A, and there is about 0.05 ohms of resistance on the exposed terminals, 45 W of pure heat is produced.

Need to push the fuse further in and flush with the board and minimize the resistance with my hoof soldering iron tip tomorrow.

My screw driver tip loses heat quickly :(

Finally replaced the MDP1933 MOSFETs with beefier IRFB4110 MOSFETs, but boy was it expensive!

Whenever we replace blown MOSFETs, its a good practice to replace the entire array even if one MOSFET is blown and the others work perfectly fine since you never know if the voltage spike or whatever calamity had partially destroyed it (it would fail to close properly, dropping a lot of voltage)

Atleast the inverter’s been fixed now (or is it..?) and outputs a clean 230 V RMS.

Tested with a 20 W lamp and it works well.
Need to replace the 35 A automotive fuse on it as well since it was also blown due to the direct short that occurred, I’m using a piece of solder wire as a temporary substitute (not recommended btw)

Need to test with bigger loads to ensure that its back at business and nothing else was damaged due to the overload.

Also worked on the Instructable for the past two days while waiting to get the MOSFETs.

Switching to daily devlogs from now on..

Worked on the broken inverter.

Tried replacing the MOSFETS with a different ones.

The original ones were MDP1933, with a drain to source resistance of less than 5 milliohms, while the ones I replaced with were IRFZ44N and featured a drain to source resistance of 15 milliohms.

I need to find a stronger MOSFET than the original MDP1933 used in the build and also upgrade my table’s sticker to gray :D

After a full 2-week fever, I’m back into business :D.
Things aren’t great to start off. To sum it up, the inverter died after I connected a chineese steamer apparently rated for “120 W”, when in reality, it drew around 500 W from my wall. My inverter tried to maintain its voltage and ended up killing its MOSFETS. I really hope the MOSFETS are the only ones damaged.

Had to tear the unit down, do plastic welding since the screw mounting slots broke.
Probably I would rate this as a 0/10 in the reparability scale by myself -_-.
Also, bypassed the 10 V regulator on the charger boost converter module and now it can work from 9V.
Planned to add another separate boost converter for the inverter to prevent inverter’s low voltage protection from kicking in.
Bypassed the regulator here as well. I feel kinda lazy and tired, probably will log more time from tomorrow,,

Had to harvest a boost converter from my old bench power supply, fix it (it was dead shorted due to an internally shorted capacitor)

Planning on adding a pre-boost converter for the inverter and the charger functions. They refuse to work below 10.2 V, disregarding 20~30% of battery capacity.

Recorded the voltage, current, milliamp hours, power drawn along with time stamps. Gosh, my hands are numb now -_-.

Welp, killed another boost converter. This one failed by having its output voltage always equal to the input voltage no matter what, unlike previously where the boost converter failed as a direct short.

Other than this, I spent a lot of time troubleshooting the charging MPPT function, which seemed to not have proper limit and tripped whatever charger I had connected it to. Had to change the values quite a bit but nothing helped.
In the end I noticed that the initial_in_voltage variable was set to the absolute minimum trigger point whenever the charger was connected, therefore the condition where the (initial_in_voltage - in_voltage variable <= 0.2) inequation is always held true and therefore the Arduino ramped up the PWM no matter what, it took a ton of time to figure out -_-
In addition to this, I had also spent a around 2h in testing the power station regarding its thermals and max. power capability..

Successfully completed the soft started board in order to prevent the inrush current drawn by the XL4016 module from tripping certain chargers. It felt endless, I had to use 2 NPN transistors in an inverter configuration in order to not use a PNP transistor since I did not have one lol.

Also 3D printed and replaced the old battery case for a newer one which has ventilation holes, helping in keeping the battery temperatures low..

In the process of making the soft starter circuit for the XL4016 module, since the inrush current trips some chargers, I’m set on using a 555 timer chip in order to turn on a relay 2s after powering on the relay.

Anyways, tested the bare-bones version of the power station at around 100 W and/or 10A of current and it worked beautifully, though I was scared to my core when doing so, not wanting this setup to blow up like last time which killed the boost converter and both the charger modules.

Printed the left side panel, tried to print the bottom panel but failed, also the BOM list final is ready!!

Well, seems like the assembly process is going to be hard due to a ton of wires and obstacles :(

Had to trim the direct source connector panel twice for it to fit in the right side panel
Boost converter module is held under really high amount of tension probably due to 10mm bolt and nuts.
Made orientation and placement mistakes while installing the chargers panel -_-

Looked through the designs and measurements, edited them when necessary, tested the charging circuit, not sure why but it trips my MacBook’s PD 30 W charger but not my Samsung PD power bank, probably due to inrush currents.
After a long conflict, finally printed the right side panel, need to proceed with the left, top, bottom and back panel as well.
I don’t know, I’m scared to waste ~100g of filament and ~10h of time over a failed print just because of a dimensional mistake or inaccuracy, I’m just looking through the final model in Fusion 360 countless times,!

Birthday devlog today🎉!

Did a ton more of CAD work, including modification of slots and sketches, and boy was it painful!. I had to re-draw each sketch on top and repeat this once again since I need one for negative extrusion and one for filling the already existing slots. All caused by my poor judgement of the dimensions of the other parts

But here I am! Also, had tweaked the code a little, did some power wire replacements and stuff

Working on the mainboard mount.
The mainboard is planned to be mounted on top of the battery pack. Not sure how I’m gonna figure out how to make mounting holes on the bottom panel. Its 12:20 AM rn, need to go to bed,,,

Probably a really messy workbench right now.

Anyways, once again, did quite a bit of working, especially in CAD and 3D printing.
Finally, I’ve hit 100% of the program storage space in my Arduino Nano when uploading my code. Need to optimize the code.
Had to snap off the screw mounts and the bottom section of the button mount cover for it to fit, fixed it in the later version though.
Also, spent 5 full minutes troubleshooting, opening the mainboard out of its case only to find out that nothing was connected (power button, navigation buttons, etc.). Probably, late night fatigue kicking in,,

Printed out the front panel, got a ton of work to do on the other panels.
Thinking of whether or not to add a fuse in series to the direct source connector..
I feel like fitting all of these components into their designated space might be a very tedious task.
Its just a pain to measure and ensure everything is in its own designated region and every part seats in properly, and also, found a mini bug, which is to be fixed in the code,,

Printed and assembled the chargers part

And also, I’m in the middle of designing the right side panel, gonna take up a ton of time as I’m using hit and trial method

Completed the modelling part of the inverter case, charger panel and probably also the front panel.
Did some minor bug tweaks in the code
Also finished cutting the copper sheet for the inverter module

TERRIBLE NEWS: I lost 3D models of the main front panel, the inverter case AND the chargers panel to a power outage. I know I should’ve saved it but I either complete it and save it or just have them lying in my RAM overnight till it finishes and that power outages are rare for me, but here I am!

Completed the bench power supply part, printed the front side in orange and screwed it on the gray bench power supply mount since I’m planning to use orange on gray as opposed to gray on orange.

Also added an extra master XT60 connector for direct battery access connections.

Officially over the 100h mark! 🎉

Designed the front plate of the chargers, designed a stencil to drill through the copper sheet that acts as a small ‘heatsoak’, soldered some cables and much more

Did quite a bit of various work today, but the one that made me glad is the successfull printing of the bench power supply part after 5 devastating failed attempts.
Designed the case in Fusion 360
Worked on the header connections
Worked on the bench power supply part

Completed the case for the inverter part, switched to digital operation of the fan instead of analog due to never ending problems.

Completed the addition fan and LED interface to the mainboard. I had to add a separate boost converter to the setup.
Still the addition of fan causes fluctuation in time to empty readings, need to fix them in code,,

Finally completed the haptics part, there are still some areas that do not work like intended, but I cannot really do much about it.
Designed as well as printed cases for the main board and batteries for enhanced safety.
My streak has not extended for today despite 3h of work today.,

Worked on the haptics for quite a while, still need to add haptic feedback/notification for other messages displayed on the screen, though it is SOO BUGGY! I had to work on it for 3 full days, yet I still feel like the haptic patterns were inconsistent, gotta do more fixing tomorrow, or probably I might focus into something else for a while.

Messed up and messed around using millis(), need more time to debug and fix it (I’m not an expert when it comes to dealing with millis(), open to suggestions), I don’t want to use delay() since it interferes with my mAh measurement in the code.

Did a weird contraption of a capacitor, polarity protector diode on a perf board in order to act as a power distribution board since the boost converter had only 1 screw terminal..

I have planned to integrate haptics to the power station too, though traditional ERMs felt too cheap and unreliable, therefore I made something called the “Haptic block”, an LRA (Linear Resonance Actuator)-based haptic actuator, similar to the ones found in flagship smartphones (I’m looking at you, iPhone 6S!). Used a 12V, 6N solenoid along with a MOSFET, resistor and a flyback diode for switching the solenoid with the Arduino board.

It works great, started with the coding process, the timings have to be perfect, else, it feels like metal and plastic colliding (though that’s exactly what’s happening XD).

With perfect timing though, it enhances the user experience by a lot!

Took quite a while to try various methods, debug, fix, etc. the MPPT charging. Finally, a transistor pulling the floating 100mV to ground along with an RC filter seems to work, works for now, though not the best way of doing this.
(Literally screamed in joy when it finally worked lol :D)

A week’s worth of devlog, probably I’m gonna switch over to weekly devlogs cuz I’m a bit lazy. Anyways, once again, a ton of changes:

1. First and foremost, replaced the charger modules and the boost converter (Boy was it expensive for me).
2. Added ADS1115 ADC as I needed an extra analog pin for measuring input charging voltage, switched voltage, current and temperature measurement to there as well.
3. Planning on adding 2 more temperature sensors, 1 for the battery and 1 for the charger modules.
4. Working on charging part for now, gonna use MPPT.
5. A mystery addition that I bet nobody can guess (its in the image btw), open to your guesses btw.

A lot of changes and events.
Spent almost an hour modifying/testing the charging lightning icon on top of the battery.
Fixed the mAh counter
Fixed the time to empty counter
Edited the power value such that only positive values are shown
Killed the boost converter and charger modules, still unsure what caused it but I suspect the boost converter overheating and then finally, a voltage spike killed the charger modules too.
Any ideas/opinions are very helpful..

After 800 lines of code, I finally hit the 2kB RAM ceiling. Did some optimization work on the code. Had to take a backup of the flawless code, try new stuff, in split screen mode between 2 IDE screens

Completed the chargers part (mainly fixed the power measurement bugs).
In addition to that, did the temperature controlled fan part for today, so far works perfectly.

Finally completed the soft-latching power control part in the circuit.

2 Arduino nano(s) were k1lled during the process :*(.
Used an N channel MOSFET at first in order to control power going to the Arduino, failed at it, switched to a relay (big mistake), driven by a transistor, finally got out, bought a P channel MOSFET, still driven by an NPN transistor, and in the end, it works flawlessly, gave me immense happiness watching it work flawlessly :D

Did more soldering work, not the prettiest, has a ton of improvements to be made both on the hardware as well as the software side.
So far, the charger and the inverter switching part works, need to add a transistor in between the system and the battery in order to turn it off completely when not in use..

Open to suggestions and improvements..

Burnt some midnight oil to disassemble the breadboard prototype and start with the actual circuitry, soldered a few components so far, yet there’s a lot more to do so, probably gonna take a month to complete -_-.

Worked on the settings screen for a while. Added maximum power limit as well as basic RGB LED colour setting along with EEPROM memory to store the parameters

Completed drawing the sketch of the portable power station (sorry for the messy work, its the first sketch). Please let me know of any suggestions/improvements..

Did a lot of tidying and reposition work as well as addition of various controls toggles on and offs.

Added 2 pages: Controls and Info, settings page is still pending..

Replaced the 20 A BMS with a 40 A one, in order to achieve the full 27 A capability

Started with the framework of the icons for turning the outputs on or off.

Re-positioned the screen page indicator, fixed a bug that that was present since the start
(fun fact: I thought that it was not possible to fix that till yesterday till I remembered “break” statement exists thanks to a dream I had last night using break statement to fix the same)

Added some adjustments, possibly also a framework of multiple screens.

Completed the temperature reading, temperature warning, as well as temperature controlled fan pwm signal.
Bugs:
Temperature and PWM value fluctuate greatly when connecting an LED as a test for PWM regulation

Bare-bone version of the code is ready, works without any major bugs..
Next step: Continue coding of the remaining features and functions
(Tested and verified on my trusty breadboard setup)