This is recreation from scratch of the first DSO Shell + battery + usb charging The freecad source file is included if you want to modify it

It uses a TP4056 to charge the battery and a boost converter to bring it up to ~ 8.5v You might have to filter the DC/DC output if you see a lot of noise (not significant in my case)

The part list is the same as the first version :

• Boost : https://www.ebay.fr/itm/5PCS-MT3608-2A-DC-DC-Step-Up-Power-Apply-Module-Booster-Power-Module-for-Arduino-/201206848274?hash=item2ed8dcdb12
• TP4056 including protection cirtcuit : https://www.ebay.fr/itm/5PCS-5V-Micro-USB-1A-18650-Lithium-Battery-Charging-Board-Charger-Module-/400665524431?hash=item5d4986b8cf
• Switch https://fr.gearbest.com/diy-parts-components/pp_237508.html?wid=21

Some tips :

• You need to use support, and they are a pain to remove, but it's doable
• You'll need to clip a bit the original power switch if you installed it.
• If you use large battery like in the pics, space is very tight. But you can use smaller battery such as the ones for nokia 3110. There is not enough room for 18650, but smaller ones can fit.

/!\ Be careful, some of the boost converters on Ebay have the wrong potentiometer value. It should be 100k (104) and it is 1k (102)