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I am powering an array of LED lights via the car alternator (the LEDs are connected to the car battery leads, but only run when the engine is on). The problem with this setup is that the natural alternator/battery voltage spikes cause the LEDs to flicker slightly. I would like to remove this flickering, however I am unsure how. The setup is an array of 12v LED strip lights. Should I use capacitors or some other method? Note that there is a large number of individual LED strips, totaling about 30 amps of current draw.

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  • \$\begingroup\$ You'd need a massive capacitor to smooth this out very much. You want a proper power supply/voltage regulator most likely. \$\endgroup\$ – Hearth May 8 '19 at 19:13
  • \$\begingroup\$ All power supply solutions are prohibitively expensive at this scale of amperage (and voltage regulators are already being used to give the strips ~12V from the car's 14V) so I just need a simple and cheap solution to mitigate these spikes. \$\endgroup\$ – James R May 8 '19 at 19:19
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    \$\begingroup\$ "Simple and cheap" and "30 amps" don't really go together all that well. \$\endgroup\$ – Hearth May 8 '19 at 19:27
  • \$\begingroup\$ LEDs don’t normally switch themselves on above 13V, so there is a design fault in this unknown string \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 8 '19 at 21:48
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A high-quality car capacitor should work. The bigger it is the smoother the signal. Bigger capacitors do take longer to charge and cost more.

Amazon has these.

Just be careful it does not short, there is no overvoltage, it does not get connected backward, and it can handle your current load. If something is wired wrong, these capacitors may explode. Just make sure the top of the capacitor is not pointed to anything important and any escaping gasses can vent somewhere safe in the event of an explosion.

A fuse or better yet breaker which automatically resets would be useful to prevent a short from damaging setup.

A switch which can disconnect the capacitor when the engine is not running may save your battery life.

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    \$\begingroup\$ And a way to disconnect / discharge it so the car can be worked on safely... \$\endgroup\$ – Solar Mike May 8 '19 at 21:10
  • \$\begingroup\$ Thanks, this is exactly what I needed. Big amperage calls for big capacitance. \$\endgroup\$ – James R May 9 '19 at 18:43

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