Jump to content
CE Auto Electric Supply

Recommended Posts

Caps don't hold enough power to be useful - even nice ones will be drained in a fraction of a second

My DC5K has 24 1200uF caps in its power supply input which are used to produce >5kW.

That adds to 28,800uF.

Most basic stiffening caps are 1F = 1,000,000uF.

Still think they're "small"?

yes... still small.. the capacitors in that 5k's power supply section are not there to be the supply of power.. see snafu's post from before on how capacitors are used for many different purposes in electronics, from conditioning, to filtering, etc.

Yes, I realize that and I'm not stating that the amp runs solely off of the input caps.

They are there to reduce the ripple voltage to the power supply and stabilize the voltage.

Stiffening caps are used for the same purpose at the input to an amp.

I was merely comparing what a 5kW amp uses at its input to the actual size of most stiffening caps that people buy.

1F >>> 28,800uF.

Caps in the trunk are not meant to supply power to the amp, they are to stabilize the voltage.

This post sent with 100% recycled electrons.
2004 BMW M3
Mechman 280A
2 - XS Power XP3000

1 - XS Power D375

500F of Maxwell SuperCaps (soon to be 1000F)
iPadMini2

Dash mounted O-scope
Audison bitOne (Remote DRC MP)
Highs Amp - PPI Art A404
Hertz HSK130 (HSK165 waiting...)
DC Audio DC9.0K
2- DC Audio XL12m2

LEGAL             - 147.3dB @ 41Hz
OUTLAW         - 150.2dB @ 45Hz

OUTLAW         - 145.7dB @ 30Hz
JUNE 2014 SOTM WINNER

2014 COLORADO PEOPLE'S CHOICE WINNER

SOTM BUILD:
http://www.stevemeadedesigns.com/board/topic/141656-wicks-e46-m3-build-bass-turbo-button-and-a-big-new-addition/page-68#entry2802026

sig-sized6_zps0265e669.png

Link to comment
Share on other sites

Ready to learn.....or teach.

Vehicle: 1995 Impala SSHead Unit: Pioneer AVH-P4400BHMids And Highs: (still deciding)Batteries: 1 Deka Group 34

Time to make a race car.My Build Log: Solo X 12"http://www.stevemead...don15zzz-build/My Build Log: DC lvl 4 xl 15"http://www.stevemead...don15zzz-build-My Wall Build Log: 4 Lanzar 15's/ 3k+ RMShttp://www.stevemead...t-by-techforce/My Feedback:http://www.stevemead...1

Link to comment
Share on other sites

Nice numbers Sanitarium, but it seems SO wrong!

Can someone confirm my thought, or is it me that's in the wrong?

Link to comment
Share on other sites

This looks like a lot of headache ...lo

ivsmd.png

06 Trailblazer ss

2 Team shok industries tsx 18s
Phoenix Gold ''THE ONE''
2 Phoenix gold 800.4
4 crescendo mp6.
2 crescendo mp8
bass processor

Dc power 270xp

150ft 1/0 ofc sky high cable
1 juicebox lithium 0.5kwh 14v/40ah
kenwood dnx8120
BCAE1.com
YouTube channel : REaudioxxx1
build log: http://www.stevemeadedesigns.com/board/topic/160106-trailblazer-ss-xxx/

Link to comment
Share on other sites

J=CV^2 (J= joules, C=capacitance, V=voltage)

for a 1 farad capacitor on a system charging at 14.2 (voltage = random number somewhere around normal car voltage I pulled out my ass for the sake of this post)

J = 1 x (14.2x14.2)

J = 201.64

ok lets round that to 200

ok so 1 joule = 1 watt for 1 second.

now lets play with those numbers.

we all know amplifiers aren't perfect, power is lost to heat, etc. a pretty common number to see is 70% efficiency at 1 ohm on a class D amp.

lets say you're the typical sort of SMD person. you want bass. you want it in your face, you like the long drawn out demo music, low notes, etc.. you stive for a big, powerful system.

so lets start the number game at 5000 watts, at 70% efficiency, that amp needs 7142 watts of input.

and remember from before, 1 farad = roughly 200 joules = 200 watts at 1 second.

7142 / 200 = 35.71 . round it up to keep from getting bogged down. 36

so that's 36 joules if the amp is operated for 1 second.

lets keep playing with the numbers cause 36 farads is a ridiculous number for 1 second of play.

say you put a nice single 275 amp alt under the hood, that charges at the 14.2 as we started this whole thing out at.

wattage = voltage x amperage

275 x 14.2 = 3905 watts from the alternator

bare minimum to run the car itself is say.. 60 amps or (60x14.2=852) call it 900 watts for overhead.

so we got.. call it 3000 watts left for the system

7142 - 3000 = 4142 watts still needed for the system

4142 watts @ 1 second = 4142 joules / 200 = 20.71 call it 21 farads needed.. per second

still haven't taken batteries into the equation here but we'll leave them out of this for now.

ok so 21 farads per second, for 30 seconds of a bass race 630 farads.

So who's buying me a 630 farad capacitor bank?

This is some interesting math and don't get me wrong, I love working through some equations to figure out a problem, but it is assuming that you are running the amp totally from a capacitor so obviously you'd need a very large capacitor bank to operate the amp for any amount of time.

Your math also assumes that you are completely draining the cap to ~0V.

An amp can't really operate below ~9-10V so your usable voltage range is really only 14.2V to ~9V.

  • Like (+1 Rep) 1

This post sent with 100% recycled electrons.
2004 BMW M3
Mechman 280A
2 - XS Power XP3000

1 - XS Power D375

500F of Maxwell SuperCaps (soon to be 1000F)
iPadMini2

Dash mounted O-scope
Audison bitOne (Remote DRC MP)
Highs Amp - PPI Art A404
Hertz HSK130 (HSK165 waiting...)
DC Audio DC9.0K
2- DC Audio XL12m2

LEGAL             - 147.3dB @ 41Hz
OUTLAW         - 150.2dB @ 45Hz

OUTLAW         - 145.7dB @ 30Hz
JUNE 2014 SOTM WINNER

2014 COLORADO PEOPLE'S CHOICE WINNER

SOTM BUILD:
http://www.stevemeadedesigns.com/board/topic/141656-wicks-e46-m3-build-bass-turbo-button-and-a-big-new-addition/page-68#entry2802026

sig-sized6_zps0265e669.png

Link to comment
Share on other sites

This is some interesting math and don't get me wrong, I love working through some equations to figure out a problem, but it is assuming that you are running the amp totally from a capacitor so obviously you'd need a very large capacitor bank to operate the amp for any amount of time.

Your math also assumes that you are completely draining the cap to ~0V.

An amp can't really operate below ~9-10V so your usable voltage range is really only 14.2V to ~9V.

very good that you point out these two things,

1. your battery doesn't provide very much juice above resting voltage so essentially as soon as you outrun youru alternator, your voltage starts dropping and you start draining the capacitor bank.

2 about the capacitors, as soon as the capacitors reach the resting voltage of the battery/batteries they then become neutral to the system, ready to draw from it as soon as voltage increases again, or provide power as soon as the demand grows, for a short while.

so you can see for the purpose of pushing numbers around, putting these two things into the equation really just gums up the works and makes for more guess work in an otherwise clean exercise of throwing numbers at a board to see what sticks.

  • Like (+1 Rep) 1
Link to comment
Share on other sites

I'm just curious how much current it takes to charge a cap per farad and how quickly they charge. I've never owned one, but everyone i know swears by them. But they all have stock charging systems and dimming headlights.

Also, Can a capacitor help out with other things like the amplifier(s) for mid range speakers?

Hopefully these questions get answered.

edit:

Also, don't things like capacitors start loosing efficiency as they get larger?, I mean, not only discharge time, but discharge vs charge time?

Edited by strangeduck
  • Like (+1 Rep) 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Who's Online   0 Members, 0 Anonymous, 257 Guests (See full list)

    • There are no registered users currently online
×
×
  • Create New...