If you want to go the diy route: https://circuitmaker.com/Projects/Details/Craig-Peacock-4/LT8490-Buck-Boost-Multi-Chemistry-Battery-Charger-with-MPPT
you can request the lt8490 ic for sample for free from analog devices.
Hi. I've bought 18650 batteries from aliexpressbefore. I was wondering if anyone here has bought 18650 from Taobao as their prices are a lot cheaper. Although the cells are not "name brand" their seems to be good deals like 2600mah for $0.80 and 3000mah $1.25. These listings have many orders and...
If you don't mine cutting your own:
18650 shrink wrap cutting jig: