3.7v lithium-ion batteries (eg. 18650's)

flashlights

The batteries must be field-replaceable.

• by GearLight
• by Ultrafire
  • this company has really good advice [1] [2] [3]
• by Fenix
  • advice [1] [2] [3] [4] [5]
• by ZebraLight
• by Noctigon / Emisar
• by Convoy

Reviews of 18650 flashlights: [1] [2]

Amazing database of different 18650 flashlights. [21700] [UV]

Another database of different 18650 flashlights [21700] [UV]

power banks based around USB or QC 3.0

• [1] [2] [3] [4]
• comparison of charger/powerbanks. Most of these products have been discontinued. Products that are still available:
  • Xtar PB2 and others some support QC 3.0 also
  • Tomo P2, P3, and P4

power bank that outputs 12 V instead of QC 3.0

This could be used for all kinds of things, including RV fridges, semi-truck microwaves, you name it.

1. the power converter — [1] [2] [3, 300W] [4, 138W] [5]
   • better-known brand: Victron Orion — [manual1] [manual2] [240W] [1200W]
2. several cigarette-lighter sockets in a row — TODO
3. 3- or 4-slot 18650 battery holder(s) — TODO

Other things you could use 18650 batteries for

• https://www.reddit.com/r/18650masterrace/comments/10kdkt1/18650_powered_devices_besides_flashlights/
• https://www.reddit.com/r/18650masterrace/wiki/devices/
• https://www.reddit.com/r/18650masterrace

Full list of 3.7 volt batteries

Some of the more common sizes are 16340, 14500, 18650, 21700, and 20700, but there are many others available.

A more complete list might be — 18650 26650 21700 14500 16340 10440 16340 14650 18350 18500.

I currently own 18650's, and may buy some 21700's, since they work in both my charger and my USB-C power bank.

Other pro-tips

• 18650's can be stored for a relatively long time if kept at 20°C (68°F).