DIY Battery backup/UPS for WiFi Router, switch... 4x18650

I have a home automation system at home, and I already have an inverter on this system. The problem is that the internet box is a long way from the system, and everything breaks down when there's a power cut and the network goes down. So I was thinking of buying a second inverter, but it's very expensive and very inefficient: they convert 12v to 230v and the internet box power supply converts 230v to 12v 😂

If you include the cost of the battery, which has to be changed every 3 or 4 years, and the loss of power due to charging lead battery 365 days a year, it's very expensive.

So I decided to make a DIY 12v backup battery.

I'll explain how I did it so that you can make one for your needs:

First of all, determine the voltage you want for your equipment. In my case, it's an Orange Livebox powered by a 12v wall adapter.

I wanted to use the wall adapter, so I bought some DC Jack connectors (measure the outside and inside diameter of yours, there are all different ones...)

Here are some on aliexpress: https://fr.aliexpress.com/item/1005004640331507.html?spm=a2g0o.order_list.order_list_main.10.15745e5bYKmB9s&gatewayAdapt=glo2fra

I also bought a card that manages the protection, charging, discharging and conversion of all this.

I found this (which I'm using in this project): https://fr.aliexpress.com/item/1005006743236692.html?spm=a2g0o.order_list.order_list_main.60.15745e5bYKmB9s&gatewayAdapt=glo2fra

it is for 12V or 15V (read the documentation for detail explaination)

But you can use this card: https://fr.aliexpress.com/item/1005006243706665.html?spm=a2g0o.order_list.order_list_main.34.15745e5bYKmB9s&gatewayAdapt=glo2fra

There are many different versions with different voltages! Choose the one that best suits your needs.

Then follow the documentation for the card you buy, particularly for wiring.

For the 18650 battery (you can use other li-ion batteries, but again, read the board's documentation!), I printed out this customisable part (shame it's not printable...): https://www.thingiverse.com/thing:456900

Connect it all up and you're done!

I decided to add heatsinks (homemade at work 😉 , but you can buy cheap ones on aliexpres) as the board gets very hot when in use (only when charging or on battery)

I also added feet to the case to increase airflow (ventilation under and over the PCB). The feet don't need any screws or glue, they fit perfectly into the box (you may need to sand them down if they're too tight, depending on your printer settings!)

The cap clips neatly onto the case and holds everything together. No need for screws or glue!

There is 2 location to put to status LED (my circuit card provide this, so I put this 😂) It provide information on the actual state of the system (battery failure, power outage, battery charging state…) 

I print everything in 0.2mm thick black PETG. PLA and ABS work too !

The next step is to integrate an ESP8266 to manage everything in the home automation system (indicating the state of the battery, the time before power-down in the event of a power cut, periodic automatic tests, etc.).

If you need any details or explanations, don't hesitate to ask me, I'll be happy to answer!

And post your make, upgrade or modification ! I'll be happy to see this 😉

Note : Links are not affiliate ! 

Note2: I'm not responsible for what you can do with this. Always be careful with electricity, even if it's low voltage: short-circuiting a Li-ion battery can lead to a disaster !