Cap questions

[blind34_1]

Okay lets see if I get a response to this or just blank stares...

I'm to be running enough of a load in my car to where my headlights will dim and the alternator wont put out enough. a new alternator is not an option right know (later, during engine swap), so I'm considering cap(s).

1 farad caps are expensive, and I'm poor. So I'm looking for a cheap solution, tell me if this would/could work:

I can get low value caps for cheap. These are the big blue caps bigger than a soda can. If I were to wire a bunch of these caps in series, does the benefit of having them make a comparable difference to buying a big 1 farad? I'm asking are the capacitances additive?

[94_AcCoRd_EX]

I'm not sure about the performance, but you'd wire the smaller caps in parallel ;) I just f'd up an electronics lab when I wired them in series :o

Hmm... what value caps can you get? I think that you'd want to wait and buy a real one. First though, how many are you talking about hooking together?

[sc0rch]

caps dont necissairly save the battery....they just store power for deep bass drops when the amp is pulling 12v or over for a long time.....if the cap is dry from pulling over 12v then the alt and battery are still being effected......caps are not a good alternative to a new Alt or isolated battery

[sc0rch]

also.......you can have an Alt rewound for about $100 but it just rewinds the copper and doesnt replace the guts.......so it wont last forever

[Non_Affiliated]

First off, Caps when Wired in parallel, The capacitace of each cap. is addative and the Voltage rating is only as high as the lowest voltage rating of the two or more caps.

Now wired in series the the Caps Farad ratings are 1/(1/C1+1/C2+1/C3+......) In other words you take the capacitor 1 and Inverse the value, that is the 1/X button on a calculator. Then you do the same for Capacitor 2 then add those valuse together, then the inverse of that. Which will equate to a lower capacitance, yet the working voltage of the caps will be addative.

So let say you have two 0.5 Farad caps with one having a DC working Voltage of 20V. The other has a DCWV of 16V

I Parallel, that would equal a 1 Farad Cap, yet you would only have a DCWV of 16V.

Now with these connected in Series that would make it equivlent to 0.25 Farad cap, yet it would have a working voltage of 36V.

Now on to the other part, Don't get the cap. First I would suggest looking at the wire for your battery grounds, and the power wire that runs from your alternator to your battery.

While commonly overlooked, The Alternator to battery wire most people will forget when up-grading to a higher power handling system. While you add bigger power wires for amplifiers, the wire gauge in the front end of the electrical system doesn't get changed. Why? It should especially if you have increased the currnt load on the alternator.

Second People use big wire going to the fram of the car, well the car chassis is not the end of the road for the current flow. remember when you added that big fat power wire to the amp in the trunk or hatch, you really should look at the return path to the battery. How come some forget to replace that old factory ground, or add anothe Ground wire to the battery? Not sure but It commonly gets over looked. Remember if you are drawing 50A from the battery, that same 50A sould be returning to the batts negative post.

So I would say first I would see if that may help. Remeber though if you are drawing signifigantly more current than your Alternator can handle. Bigger wires, Caps, or what not is not gonna help dimming.

[blind34_1]

thank you, thats what I needed. To this day I still blow little caps in my elelctronics labs.

And I didnt even consider bigger wire from the alternator...thats a good point!

[Civcity]

Originally posted by Non_Affiliated
First off, Caps when Wired in parallel, The capacitace of each cap. is addative and the Voltage rating is only as high as the lowest voltage rating of the two or more caps.

Now wired in series the the Caps Farad ratings are 1/(1/C1+1/C2+1/C3+......) In other words you take the capacitor 1 and Inverse the value, that is the 1/X button on a calculator. Then you do the same for Capacitor 2 then add those valuse together, then the inverse of that. Which will equate to a lower capacitance, yet the working voltage of the caps will be addative.

So let say you have two 0.5 Farad caps with one having a DC working Voltage of 20V. The other has a DCWV of 16V

I Parallel, that would equal a 1 Farad Cap, yet you would only have a DCWV of 16V.

Now with these connected in Series that would make it equivlent to 0.25 Farad cap, yet it would have a working voltage of 36V.

Now on to the other part, Don't get the cap. First I would suggest looking at the wire for your battery grounds, and the power wire that runs from your alternator to your battery.

While commonly overlooked, The Alternator to battery wire most people will forget when up-grading to a higher power handling system. While you add bigger power wires for amplifiers, the wire gauge in the front end of the electrical system doesn't get changed. Why? It should especially if you have increased the currnt load on the alternator.

Second People use big wire going to the fram of the car, well the car chassis is not the end of the road for the current flow. remember when you added that big fat power wire to the amp in the trunk or hatch, you really should look at the return path to the battery. How come some forget to replace that old factory ground, or add anothe Ground wire to the battery? Not sure but It commonly gets over looked. Remember if you are drawing 50A from the battery, that same 50A sould be returning to the batts negative post.

So I would say first I would see if that may help. Remeber though if you are drawing signifigantly more current than your Alternator can handle. Bigger wires, Caps, or what not is not gonna help dimming.

Sounds like you have either done this before or you are an electrican:confused:

My understanding of parallel is when you wire it this way which ic negative to negative I believe then you are actually increasing the available amount of power right? Just my understanding I could be wrong!

[MAXed Out]

just do it the right way the first time even if it costs more or just don't do it at all. but i dunno they might work though

[Non_Affiliated]

Originally posted by Civcity
Sounds like you have either done this before or you are an electrican:confused:

My understanding of parallel is when you wire it this way which ic negative to negative I believe then you are actually increasing the available amount of power right? Just my understanding I could be wrong!

I have a degree in electronics. That doesn't mean I know it all I just have some knowledge of the theories, and understanding of electronics.

But to Blind34_1 Question. Personally I have done this before. Measure your battery tray for length and width. Then find the maximum allowable height for a battery taking into account the Post height.

Now bring a ruler down to your local Wally world or Costco, or where ever. I personally wnt to Wall-Mart and spent $50 on a Group DT-1 Truck battery. It was 925CA amd 720 CCA with a 100 Min reserve capacity. I stuffed it under the hood of my old '80 accord. Which was quite the step up to the punny little battery that waws in there. Not to mention I Had a 60A alt. I ran a PPI A600 and PPI A204.2 toataling 800 Watts RMS, and Being Class A/B they drew quite a bit of current. Having that moster battery under the hood helped a bit in dimming lights. It didn't cure it but it was a decent alternative to a HO alt, considering that back then it would cost around $600 for a 150A alt for my car. Today HO alts. have become quite a bit cheaper.