Introduction: Ultra Small Portable Power Supply
Finally after a really busy time I finished a new project just a few days ago.
Why to hell should I need this
My main lab is in our stairwell, there is almost all my equipment, but sometimes specaly with arduino or raspberry I like to sit in the living room at my desk. But my living room is not my lab so there is no place for large heavy loud... tools. OK and I think my wife won't be happy when I move my lab to living room. So I needed a small PSU for some testing.... and here we are ...
1. It is a fully battery powered Bench Style PSU in very small form factor.
2. It's quiet cheap all parts together about 40€
3. It's really powerful 0-20V 0-2A
4. It's easy to build really just put together some parts and that is all, hey I made it so you can also made it.
5. It's informative, it show input voltage, setup voltage, setup amp, output amp, output power
6. It can work as constant current or constant voltage
7. It can store up to two settings voltage and current
8. My iconic wooden case design all done with knife and glue
Battery Pack: 16,8V, 2500mAh, 42 Wh
Output: 0-20V, 0-2A
Size: 11,5cm x 12 cm x 5 cm (I'm from Germany we use cm, sorry guys should be about 5"x5"x2"
Step 1: Parts No. 1 - the "three" Parts
Go shopping and send me chocolate.
the first picture show the more special parts you need for the project and maybe you have to buy.
DC/DC Boost Converter [link for DC/DC module]
after I contact banggood they now have the original modul I used in my project in stock for an very resonable price under 5 Bucks, thanks to my friends at banggood for their great service.
Battery Pack [link for bms]
First part is a battery pack I build this from 4 x 16850 Li Ion batteries (4,2V 2500mAh) that I have just salvaged from a broken power tank, because Li Ion batteries are a little bit tricky I bought a BMS (battery management system) for 3 or 4 cells. How to solder the BMS to the cells you find in the specs of your BMS Modul.
Boost Converter [link to DC/DC converter]
My battery pack has an output from about 12V to 16,8V but for the last Modul I needed about 23V so I just boost the voltage with this module.
PSU Modul [link for psu module]
Here all the magic happen, just power it with 23V and you can play around no heat-sink needed because it is a DC/DC converter and very effective of course the voltage from a classic linear converter is more clean, but not very useful for some battery powered devices.
Step 2: Parts No. 2 the Really Common Parts
1. From step up converter to PSU module
2. From battery pack to charging port
3. Switch between battery pack and step up converter
4. Red binding post from PSU module to front panel
5. Black binding post from PSU module to front panel
6. ohh dammit not on picture a black wire from battery pack to step up converter
Step 3: Get Out Your Knife or Laser Cutter or What Ever You Use to Work With Wood
My case is made out of 4 mm plywood I choose this because it is easy to use and don't need any special tool. The dimensions in the wonderful hand painted blueprint are for 4 mm plywood if you use other materials you have to make sure you also change the other dimensions otherwise it would not fit, or you just build your own design.
Step 4: Glue Everything Together
After I cut all the parts from one sheet of plywood I just glue it together normally I use some tape to make sure it fall not apart while drying.
Only the lid I did not glue this will be later attached with some really tiny screws.
Step 5: Sand It, Paint It and Polish
my cases don't need to be perfect but I like it smooth so before I paint them I sand them, also good when you don't work so exact because a knife is not a laser cutter or a cnc or it is just me always in hurry.
I just have some leftover from those brown wood color so all my projects now get this paint, i like it and it looks also a little bit vintage, after I apply the paint i just wait for a few minutes and then I finished it with some bee wax laying around in the basement.
Just get some of those sticky silicon bumpers for underneath make the psu more stable on the table.
Step 6: First Run - Testing the Electronic
to be honest before I build the case I made a proof of concept prototype where I just throw together all the parts also useful to build the case and see what space I would need. In this picture you see my electronic load, this is the reason I come to instructables I see this instructable for the electronic load and just build it and when you are building a PSU there is nothing more useful then an electronic load.
Link to the great arduino controlled electronic load [link]
Electronic Load Modul [link]
Step 7: Throw Things in the Box
hey we are coming close to the final steps and a hopeful working cool device.
Here you see how I placed all the parts in the case.
You also find another of my wonderful unique technical drawings 100% handmade by myself, use it to do all the wiring but be careful it is quiet a lot of power in this small box.
Step 8: TEST IT.............. Yeah We Are Done
Of course charge the battery before, I used my Bench PSU for this job, I just setup 16,8V constant volt and 1 amp constant current.
Power it up, and it should work.
Congratulation from my knowledge you have one of the first battery powered bench performance PSU in you hand and can start with some projects.
For example power a raspberry with it or whatever you want.
Step 9: Compare Noise From Bench Psu and Battery Powered Psu
Here I will just show you my result of a little test I made with the PSU to check the noise I got under test with about 15 Watt output power.
- Bench PSU and my battery powered PSU
- Both are set to 10V
- Electronic load set to 1,5 A
- DSO 100mv / Div
You can see on the second picture that I have more noise on the battery powered PSU but that is what I
expected from the through the DC/DC converter I used but until now I could not find any problem.
Step 10: Get Ready for New Projects
Hey people at the beginning I already say I'm quiet busy. So she is the reason why, my little girl "made n china" but now she is already 6 months so it is time to train her on the computer I think with 1 or maybe 2 she can start to build things with me.