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I am designing a chainable module of three parallel LED strips with individually addressable LEDs (WS2812B @ 144LEDs/m). When connecting one module to another, each LED strips data channel of the one module will be connected to the Data channel of the corresponding LED strip of the other module. So no matter how many modules I connect, it will act like three long LED strips.

The power of each module will be provided by its internal batteries only. The ground wire is passed on to the next modules, so that all modules share the same ground.

The power is provided by four 10440 Li-ion batteries in parallel, which are connected through a BCU.

I use four batteries per module, since The BCUs cutoff current is 4A, but the maximum current I can draw from a single battery is 1 A. So using 4 batteries in parallel would make it possible to draw 4A from them.

The total length of all the modules I will connect will be around 1.5m (so 3 LED strips with ~1.5m each)

My questions:

  • Does current flow through the ground wire between the modules? In theory not, since the whole circuit is complete within the module.
  • Does the ground wire connecting the modules need a particular thickness? Since no or very little current flows, I can use a thin wire, right?
  • Assuming I check that the batteries are charged to the same voltage before putting them in, is it safe to have them in parallel like this? I have read somewhere that I'd need to put a resistor between the batteries to limit the current in case they are out of balance and start charging each other, but wouldn't that drain the batteries to death?
  • Do you see any other problems with my diagram?
  • \$\begingroup\$ I see many uncertainties and GND is just a label where you define 0V. ANY current to shared grounds may disturb that 0V. WHere is the datasheet for every part? \$\endgroup\$ Commented Sep 7, 2022 at 16:14
  • \$\begingroup\$ Diagram does not match text very well. || Batteries MUST be matched before paralleling. eg charge each fully independengly first. Once paralleled they usually work reasonably well. || Assumptions re ground sound reasonable. Star connect grounds to a common point to avoid drop along ground lead causing signalling issues. \$\endgroup\$
    – Russell McMahon
    Commented Sep 8, 2022 at 11:12

1 Answer 1

  • There will be a very small AC GND current between the modules.
  • You need a low inductance GND wire to not corrupt the data, > 0.75mm².
  • Cells in parallel are OK if balanced well before combination.
  • Use series resistors in the data line (30-50 ohm)
  • I2C over this distance has poor chances. Shield it, strong pull-up and low frequency. VGA monitor cable provide this, so it is not impossible.
  • \$\begingroup\$ Would you recommend connecting ground and power at both ends of the LED strips? \$\endgroup\$ Commented Sep 8, 2022 at 2:27
  • \$\begingroup\$ @Jasen No, do not feed the battery voltage along the chain \$\endgroup\$
    – Jens
    Commented Sep 8, 2022 at 16:35
  • \$\begingroup\$ not through the connector just to both ends of the strips. \$\endgroup\$ Commented Sep 11, 2022 at 7:37

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