Compact Battery box for 9x 18650 cells

I needed a small 12v power box for drone flying/Amateur radio outings.

Designed this one along similar lines to my other battery box with a battery fuel gauge and a single Anderson powerpole connector for charge/discharge.

There are 9x 18650's in the case wired in a 3x3 configuration (3 Parallel X 3 Series) This gives an output of 12.3v at full charge dropping to 11.1v at empty.

Depending on the capacity of your 18650's you can get a nice little capacity battery mine were rated 2600mAh so this worked out to around 7.8A (claimed!).

I used a small 10A BMS board which can be found on online sellers. Search for "TS-P134" -3S 18650 10A BMS Charger.

I used a model found online for holding the cells but include one here that will work just as well here for a complete design just print 2 of these (one for each end of the cells).

The battery fuel gauge can be found online and will do 1-8 cells and come in various colours. The small tactile switch can also be found online. I hotglued these to the underside of the lid.

The seperator isolates the batteries from the BMS board and the fuel gauge, fuel gauge tactile button and main output terminals. I used double sided tape to stick the BMS to the seperator plate.

I would ALWAYS recommend sourcing good quality batteries. Any 18650 advertised being above 3500mAh is a scam. If you want to learn more google a report: "Lumafield Battery Quality Report" this is good reading on why you should stick to reputable cell manufacturers. (I am in no way affiliated with the authors).

If you are working with 18650's please take great care and do your research on these as they have a high energy content and things can go bad very quickly if you short them. The rest is on you!