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This is not yet a finished project intended as instructions but only a means to share progress on the project.

This might be dangerous to attempt !!!

If you attempt to follow any of this, you do it at your own risk.

Adapting a mains AC led bar to work with a battery of 18650s

by lepi(lepi at-a

KiCAD files:

Revision 0.1


The purpose of this project is to adapt a 220AC UV LED-Bar to work with 18650 cells.

I have just started learning electronics, and my knowledge is very basic.


The LED Bar - Light4Me LED UV 8

Characteristic Value
Voltage: AC110-240V, 50/60Hz
Power: 30W
Light source: 8x3W UV LED
Light angle: 65°
Light wavelength: 390-410 nm
Dimensions: 450 x 50 x 40 mm + 55 mm pins
Weight: 0,6 kg
LED driver inside (IP65):
Model: ZW0820
Power: 27 W
Input: AC85V-265V 50/60Hz
Output Voltage: 27-36V DC
Output Current: 600 mA ±5%
TA: 60 °C
TC: 80 °C

18650 Cells

Characteristic Value
Datasheet: ([“datasheet”]
TME Symbol: Samsung ACCU-ICR18650-26H
Rated voltage: 3.63 V
Capacity: 2.6 Ah
Maximum current: 5.2 A
Charging Method: constant voltage, limited current
Charging Voltage: 4.2 V ±0.05 V
Charging Current (standard): 1300 mA
Charging Current (max): 2600 mA
Diameter: 18.4 mm
Length: 65 mm

Battery charger - Tangspower TP-L8S20 Li-ion charger

Characteristic Value
Maximum Voltage: 8 * 4.20 V = 33,6 V
Charging Current: 2 A Passive, PFC filter

The Story

Revision 0.1

A friend of mine performs POI with POI-tails that are neon-yellow. The thing is made to shine in UV light. Some AC mains LED bars I have, revealed a lot of space inside the casing profile - more than enough to house 8 18650 cells.
The LEDs have a “PowerLed” package soldered in-series upon a pcb with no other elements, but most likely have some resistor inside the package, as multimeter LED tester does not show anything when testing a single LED.

Remembering next-to-nothing about Electrical Circuits, I started designing a circuit, that would: - Power the LEDs from cells - Allow charging the cells without taking them out - If possible leave the original charger with mains connection

First I considered two solutions: - LEDs and cells in parallel

  1. Operating current would be 0.6 A * 8 = 4.8 A
  2. Charging current would be 1.3 A * 8 = 10.4 A

- LEDs and cells in-series

  1. Operating voltage would have to be 26.9 V (3.36 V / LED)
  2. Charging voltage would have to be 8 * 4.2 V = 33.6 V


- I have a TP4056 03962A Lithium Battery Charger with protection module

- Initially I thought that would be crazy to put 8 of these inside - Also wiring LEDs in parallel would if I understand correctly require to put at least 40 cm * 8 = 3.2 m of thick wire - that might be difficult.


- A friend informed me to the fact, that I could use an external 33.6V charger which seemed to be easier. - And also that I could use LM317 to regulate current out of the cells to LED's - I decided to use a I/0/II switch and an IEC cord socket with the original LED driver if possible.

Emeryth suggested: - to learn more about li-ion cells before I use un-protected or multiple cells - to put some protection between cells and the cell charger - to use a DC-DC converter instead of LM317 that produces too much heat - to rethink if I need all LEDs in-series

Next Steps:

- Research Emeryth's suggestions
- Find a solution to connecting the cells

  1. decide whether to solder the cells (dangerous, potentially capacity hindering)
  2. contact weld the cells (I don't have access to a contact welder)
  3. design a 3d-printed casing for the cells with springs, that would slide into the LED bar casing
  4. remember to discharge cells before in case of soldering


projects/portable-led-bar.txt · Last modified: 2021/03/21 20:57 by lepi