Connected a pair of led strips 12 v from car 12 v battery. It starts flickering when engine running, and gradually goes to constant brightness as rpm goes high. However, the light stays constant or don't flicker as soon as engine is off. I guess current from battery is not pure DC current. Will connecting capacitor in parallel with these lights will make the flickering go away?? Thanks.

  • I've experienced this with LED headlights on my motorcycle. The stator doesn't produce enough power to keep the LED lights lit, so they flicker. As far as the capacitors - it depends on the size of the capacitors, and how much voltage/current you can charge them with. Also, they might discharge through the charge wire when the voltage drops, as the low source voltage will be drawing the power from the capacitors backwards. I'd be interested in seeing a diagram of how you wired the lights. Any automotive LED lights should run fine on 12V, and your alternator should source ~15V, even at idle. Aug 12, 2019 at 15:46
  • It's basic led strip light. It doesn't flicker when engine is off. But flicker only a bit when engine is running!!! Is the alternator outputs AC current to the 12 v battery? Then, I guess this ac current is the culprit behind this flickering. Want to confirm from your experience. Thanks.
    – Thang Tons
    Aug 12, 2019 at 16:12
  • It seems strange to me that the battery wouldn't provide a massive buffer which keeps the input voltage from causing a flicker. However, if the AC alternator output is the cause of the flicker, then I agree that a capacitor would solve it. I don't know enough to recommend capacitance though. Aug 12, 2019 at 16:29
  • Realize an alternator produces AC power, then rectifies it through diodes to create the DC current. It does this in three waves, which gives a fairly steady rate of current which the eye pretty much does not pickup. Your alternator can still function if one of the diodes goes out, meaning it will still produce the DC current to recharge the battery, but this can sometimes be seen in the lights. With as quickly as an LED bulb can turn on/off, it might be more susceptible to this. All this said, I wonder if one of your diodes might be out in your alternator and you've not noticed it? Aug 12, 2019 at 16:58
  • But the inbuilt headlamps doesn't flicker at all at any case!!!
    – Thang Tons
    Aug 12, 2019 at 17:08


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