Mike- N7ETA
A few years ago, I decided to upgrade my PC. In researching, I found a mini fan-less PC that runs on a 12v wall wart. After researching my software wouldn’t have any issues I purchased and installed the software I use.
The only issue I had was that even with my off the shelf UPS system the PC would reboot during bad weather. I investigated and found the wall wart was susceptible to power line transits.I thought about using one of my ham radio power supplies, which I thought was way over kill.
Searching the internet I found that battery operation was preferable. But then again it was much more than I needed. Then on “YouTube” I found them using an oversize AA with a voltage of 3.7v. This is actually called a 18650 cell as the designated size. What was impressive was the different capacities viable on “Amazon”. These cost from $2.25 in multiples and capacities from 2000mah to 9900mah
More research indicated I could build a DIY UPS with no switching time and a fairly large run time. Since the most time I have been without power has been less than 1 hour. So I sat down and worked out a wiring diagram. The schematics program I use is called “Fritzing”. Here is a link to the webpage for the software. https://fritzing.org/
Here is the parts list, cost supplier.
| 12v 18650 UPS BOM | |||||
| QTY | Label | Part Type | Unit | Part Number | Supplier |
| 1 | Case | Enclosure | $18.99 | Blue Metal Enclosure.7 x 4.33 x 3.1 inch | Amazon |
| 1 | 120vac to 12vdc | S-350-60 Power Supply | $12.98 | 12v @ 5amp | Amazon |
| 1 | 5.15V Out | Generic female header – 2 pins | $1.44 | Terminal Binding Post Spring Clip 2-Way | Amazon |
| 1 | AC1 | AC Power | $1.83 | Inlet Module Plug Socket Power Entry | Amazon |
| 3 | Bat1 | 18650 Battery | $5.97 | 3.7v @ 9900ma | Amazon |
| 1 | C1 | Electrolytic Capacitor | $0.35 | 470uf | Amazon |
| 1 | D1 | Rectifier Diode | $0.05 | 1N4007 | Amazon |
| 1 | DS2Y-5-DC5V1 | DS2Y-12-DC12V | $1.00 | HK19F-DC 5V-SHG Signal Relay | Amazon |
| 1 | LED1 | LED | $0.04 | 3mm Green (570nm) | Amazon |
| 1 | R1 | Resistor | $0.05 | 470kΩ | Amazon |
| 1 | S1 | Push-button | $0.53 | Momentary (NO) | Amazon |
| 1 | TP1 | BMS Li-ion Charger | $0.64 | 3S 12V 10A 18650 Lithium Battery Protection Board | Amazon |
| 1 | U1 | Buck converter | $3.24 | Mini-360 Step-up DC-DC | Amazon |
| 1 | VM1 | Voltmeter | $2.16 | 3 digit LED (2 wire) | Amazon |
| Total | $49.27 | ||||
Here are a couple of pictures of the finished unit.
The Future-
Since I also operate a couple of Raspberry Pi’s 24/7, I am refining the schematic with a couple of changes and will build one for 5v.
Mike- N7ETA (Extra Terrestrial Amateur)
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