masterelyt

Hi guys it's been awhile since I've posted on here. I have an idea of putting a capacitor in parallel with each of my head lights in order to stabilize the voltage when my subs hit. I'm a first year electrical student in college and as such I have a basic understanding of the physics going on here. I have a reasonably powerful alternator generating 150A and my calculated load for my amp is only 80A so I'm set there, but I still have momentary headlight dimming on strong kick drum hits.

Let's get this straight, these light dims are not sustained, only quick flickers. I think I can get rid of them with capacitors in the headlight circuit. The only question I really need help with is how to find the correct size of cap for this setup.

I plan on using one electrolytic cap on each light and I'm familiar with the formula for calculating energy stored in a cap.

Each light consumes 55W of power.

So using the formula for calculating capacitor energy, a .5F cap results in 51.84 joules of energy. Thats enough to sustain the light for almost 1s.
The light dimming might only be for a 10th of a second so might this be overkill? And won't a .5F cap be fairly large?

Is my thinking correct here? And has anyone else had any experience with this sort of thing?

Sonic

iTrader: (1)

Caps are a thing of the past and is only a band aid, root cause of the problem is where you should be looking at, start this by looking at your system wiring size and doing the "big three" frist.

masterelyt

I expected to get this response, I have already done big 3 and I have a decent alt I just want to know if my calculations are correct for capacitor size

Dukk

Most people won't understand what you are trying to do with the caps. They just read 'capacitor' and respond that they suck.

You could probably get away with 1/4f caps but the ones I have seen are pretty much the same size as 1/2f so get what you can find.

masterelyt

Thanks for the useful reply Dukk, any idea where to get caps with this sort of capacitance (.25, .5, 1 Farad)?

wasted911

iTrader: (2)

Car audio shops will stock them but will usually be priced fairly steep (shitty to say even though I work in a shop). Throw up a wanted ad on Kijiji and you should be able to get one used for pretty cheap.

To give you an idea, new would be about $100-$150
Used should be somewhere around $30-$70

Dukk

lol, I would just go out to my garage.

1/2f caps should pop up on ebay and craigslist. I snagged some 1/4f from a distributor for cheap years ago (DLC I think) but they are harder to find for sure. Could try an electronics repair shop or wholesaler.

masterelyt

All right thanks guys, I guess I will be on the hunt for some capacitors now!

stereo-dave

You said you are a "first year electrical student" did you mean "electronics" ? I would think that your professor would have some input for you on this? Like most others here, I would just grab my box of caps and start testing. BUt then again, I dont care that my lights dim / flicker. I say let 'er buck. The wiring to the headlights are only going to allow so much current anyways.

Path of least resistance

Dukk

^ ehh, you'd be surprised how narrow a view an academic can have. When I was taking Engineering we naturally took a section on capacitors in the eletronics class. For giggles I brought a 1f 20v cap to class one day. I thought the prof was gonna fill their pants. lol

I really 'endeared' myself to her when we got to inductors and one day I made a rail gun out of a few of them daisy chained together and was shooting 1/2" x 4" steel rods across the room.