I, like all of you I bet, have tons of USB power banks laying around, but even my largest, a "20,000"mah pack died after a few days away camping just charging my Apple Watch and iPhone. I wanted something that would last MUCH longer and be more versatile at the same time.

As this is the 21st century, we have the Internet which allows you to harness the brain of people with skills you don't poses, this means following some online guides of how to DIY the battery side of things. I then designed this enclosure around the pack, with some added features too!

The enclosure contains all the holes needed for a on/off button, a charge port, a LCD battery level indicator, 4x 2a USB ports, 4x USB Quick Charge Ports & two USB-C ports too. All those additional hardware items the case is designed around are linked below.

So, you want one too?

To actually build the power banks electronics, I used this guide https://www.instructables.com/id/DIY-Professional-18650-Battery-Pack/

I suggest you follow that, build up your pack, make sure it works and then order all of the parts needed for this enclosure.

This is version 3.0 of my original design(V1 https://www.printables.com/model/498563-24-cell-18650-diy-usb-powerbank-with-apple-watch-q) (V2 https://www.printables.com/model/498563-24-cell-18650-diy-usb-powerbank-with-apple-watch-q) to keep all the same benefits of my older design with some small spacing and sizing improvements, but be compatible with the Vruzend 1.6 battery system.

I dont have any of the newer Vruzend kits, but in theory it should be compatible as long as their sizing hasnt changed. The Vruzend kits are amazing, they let you literally clip and bolt together a battery pack. This means that even if you don't have a spot welder, you can make your own 18650 power bank! Seriously, ANYONE can do this!

Performance

In my mixture of recycled 2500-3000mAh cells from old laptop battery packs that I dismantled, i achieved a total capacity of 40,000mAh of total charge output. This was tested using a 2 amp dummy load and a USB power analyser in-line. Obviously, using higher (such as all 3000mAh) or lower capacity cells will result in different capacity numbers and drawing current in smaller bursts, giving the cells time to recover slightly would likely have yielded over 40,000mAh. Also, this is true numbers, my "20,000"mah pack simply isn't even close to these figures in reality, 90% of the sellers online significantly over-rate their packs size. Just sticking in 8 2500 mah cells does NOT mean you have a 20,000mah pack as the cells are arranged in series parallel and you have losses from the conversion to 5v.

I have created a wiring diagram for you to follow when assembling the power bank. This is attached to this Thing.

As always, be careful! 18650's pack a punch, let alone when you have 28 of them hooked together!

There are two lid designs too. One is solid and the other has a raised edge. I personally used the raised edge one and filled the inside with casting resin. This gives you a smooth, glass-like top surface rather than the rough PLA layer lines. If you want to do this, use the file called "lid.stl", if not, then use “lid_NonResin.stl”

Notes:

Supports are needed on the main body of the unit, and the lid.

This is due to the large overhangs to support the USB PCB and display windows.

Clearances are very tight, so even if your printer does amazing bridges, id still recommend using supports and make sure they're all trimmed properly before you install components.

Print the lid with the QI chargers facing up and support underneath to allow the recesses to be properly formed.

How I Designed This

Design Considerations

In the aim of being rugged, the box itself is really thick and very strong. All walls are even thicker than my last designs being at least 5 mm thick.

All the box edges around the walls are chamfered to increase rigidity of the box itself.

As a bonus, the 5.5mm input (charge) jack is always live at the battery pack voltage, so you also have a ~12v output on that jack depending on the charge state of your pack.

NOTE: The DC charger jack can be used as an output as mentioned but it BYPASSES the battery protection circuitry. Use this with caution to avoid over discharging the pack. Keep an eye on the battery indicator and once it gets to ~10%, stop to ensure you have some margin of safety.

Extra Hardware & Modules

Shopping List

You need wiring essentials such as hot glue, a soldering iron, some wire and to make it smarter you can use some crimp terminals and heat shrink. I also recommend wrapping you completed battery back in Kapton tape too (it helps prevent accidental shorts when wiring the various components up. Other than that, you'll need the following;

6x M3x30mm Screws - https://www.ebay.co.uk/itm/291112686143

Or, if you have a M3 Tap set, use Grub screws, it makes the top look much tidier as there's no exposed screw head.

M3x20mm Grub Screws - https://www.ebay.co.uk/itm/383636779270

Fake Wago Connectors Multipack - https://www.ebay.co.uk/itm/185246270584

1x - 16mm LED Latching Switch - https://www.ebay.co.uk/itm/352395057455

1x - 5.5 x 2.5 mm DC Jack - https://www.ebay.co.uk/itm/223562703966

1x - 3s Battery Level Indicator - https://www.ebay.co.uk/itm/262982640363

1x - 3s 18650 Balance Board - https://www.ebay.co.uk/itm/393111726760

2x - USB-C Trigger Boards - https://www.ebay.co.uk/itm/324302765701

1x - QC 3.0 4 USB quick charge module - https://www.ebay.co.uk/itm/164349537942

2x QI Chargers - https://www.ebay.co.uk/itm/134138354848

1x - DC-DC Converter 24V 12V to 5V 5A - https://www.ebay.co.uk/itm/275300251317

1x - 4 Port USB PCB - https://www.ebay.co.uk/itm/165269353986

This is a different model to what the box was designed for so it may need some trimming to fit. (Original one seems to no longer be sold)

1x Vruzend 1.6 Battery System - https://www.ebay.co.uk/itm/124368763264

And finally, you'll need a way to charge your battery pack. This is the exact model I purchased and has performed several charges without incident. The last few % of charge does seem to take FOREVER, but I suspect that's due to it ramping down the current in the final charging process.

1x 12.6V 3A LiPo Charger - https://www.ebay.co.uk/itm/303290069329