Home › Builds › 12 V solar lantern and power box in an enclosure: two 32700 LiFePO4 cells, USB-C and solar charging, 12 V and USB outputs

12 V solar lantern and power box in an enclosure: two 32700 LiFePO4 cells, USB-C and solar charging, 12 V and USB outputs

Bench build · Everyday gadgets · Intermediate · about 60 minutes

A rechargeable 12 V light and phone charger that fills from USB-C or the sun: about 3 hours of a 9 W bulb. A complete product, laid out the way it sits in a 300 × 200 mm IP54 box. Two 32700 LiFePO4 cells in series (6.4 V, 6 Ah, about 38 Wh) lie on the floor with a 2S BMS above them. Two ways to charge, both into the BMS P+/P−: a USB-C 2S charger board on the left wall (any phone charger, 1 A) and a solar jack feeding an MPPT solar charge board (CN3791-type) set to 7.3 V and 1.5 A, which holds a 20 W “12 V” panel at its best voltage. Out through a 5 A fuse and the front switch, an XL6009 boosts the pack to 12 V for a 12 V bulb on the right-hand jack and a USB-A port for a phone. Set both charger boards to 7.3 V (LiFePO4) before the cells go in; set the XL6009 to 12 V with nothing connected.

12 V solar lantern and power box in an enclosure: two 32700 LiFePO4 cells, USB-C and solar charging, 12 V and USB outputs: the finished build running on the simulator's bench

Build it in the labGuided build, test sheet and fault finding, free in your browser.

zencircuitlab.com/l/12v-solar-lantern-power

Parts list

Test procedure

Each test has an expected value and a pass range, like a factory test sheet:

  1. USB-C only: charge current
  2. Sun only: charge current into the pack
  3. On battery: 12 V at the bulb
  4. On battery: USB port
  5. Full pack: charging stops at LiFePO4 full

How it works

What it does: A rechargeable 12 V light and phone charger that fills from USB-C or the sun: about 3 hours of a 9 W bulb.

Build it (guided or ready-made), then run its test procedure below. Every test has an expected value and a pass range, just like a factory test sheet.

Background

The “solar generator” lanterns sold online are this inside, often with half the cells the label claims. Building it yourself, you choose honest cells and a BMS.

More builds: everyday gadgets