Using ICE at Home.

[Xiaogary]

Anyone using stepdown voltage transformer to step the 230v AC supply to 12V DC supply to power Car audio system at home?

 

How to calculate how many amphere max required for the power supply. I am using a 30A main fuse for my ICE in my car. If I shift it to home, I will need a power supply of 30A max also. But I feel mine is a overkill for a 30A on my main fuse in my car ICE. I suspect 20A is sufficient.

 

I have a 1300w max monoblock subwoofer Class D amp powering my single coil 4 ohm subwoofer 300w rms 650w max at 350w rms at 4Ohm. So is it combination consuming 350w or 1300w? Should be 350w only right?

 

I also have a Z4000 Cadence amp with 4 X 75w rms powering my front 50w rms, 120w max MB Quart component speaker actively. It should be consuming 4 X 75 = 250w in total right?

 

I also have a Alpine 9855 HU and Cadence CEQ770 pre-amp which the power consumption should be neligible. And a 1F Stinger capacitors which should be helpful.

 

If considering 30A power supply needed, I saw a 30A 12V DC supply selling $300+ at sim lim tower. Was thinking whether there is other alternative such as using multiple power supply or transformer for each amp.

 

Or in fact I dont need 30A max power supply. Calculating the rms power in total in my car, I should have abt 600w + HU and preamp's power consumption, should be abt 700 or max 800w. If 12v, P = VI, I = P/V = 800/12 = 66A. Doesnt make sense how come I am using only 30A fuse and the duse doesnt blow in my car. I suspect it is way below 30A.

 

Let's say total is 800w, round up to 1000w for play safe. Using 230v power supply, the current should be 1000/230 = 4+A. But I dont think I should calculate this way right? Since it should be on a 12V DC supply even when its at home. It should still be 1000/12 = 83.3A right? Cannot be....if so much current, confirm my 30A fuse should have already blown in my car.

 

Whats the correct way to calculate the main fuse needed in the car and whats the power supply needed at my home? Anyone with strong electrical background care to teach me?

[Headshok]

yoyo..

 

u write very cheem. for normal usage, u can get a 22A 12V power source at ard $160 at SLT (i've got one)..

 

BUT if u want more current, get a normal car battery and connect it to ur 12V power supply ( to charge it up)and the car battery to ur amp. i've seen a shop do that to run their display setup.

 

tats wat i did lah.

 

it works well normal spkrs, but haven tried for sub.but the shop had it rigged up to a sub, so it'll be fine..

 

cheers.

[Xiaogary]

I am reading up from the net before anyone answer my question.

For those interested, I have learned some at least on my main ICE fuse needed on my car.

 

Taken from this link.

http://www.canze.org.nz/bcae/fuses.htm

 

The main fuse is the summation of the current drawned from all the amps. If u have 2 amps, 20A and 50A, the main fuse should be 70A.

 

Still reading...will post more updates if I can find.

[Twnll]

Headshok, U shd try driving yr two atomics subs with at home. Would be interesting to hear how they sound!

[Xiaogary]

I think I found my answer from here.

http://www.diyaudio.com/forums/showthread/t-62703.html

 

Say I need 1000w rms. So thats 1000W/12V = 83.3A at 12V.

 

Therefore say my battery is 56AH. I can play 56A for one hour, and 83.3A for 40minutes. That does not means my battery will stay on the upper range for 40minutes bcos the charging will not be fast enuf. Thats why a capacitor will be helpful. Or unless I connect a few battery inline. The main fuse needed for my power suply should be 90A.

 

If I dont use battery, the power suppply from transformer will be cheaper, but then its not portable, or I should say I must always on power unlike having stored charged battery and can play for few minutes or half hour or even 1 hour when power failure.

[Hyun]

while u're on calculation, i suppose u could calculate how many minutes u could play your ICE using the car battery without charging it with engine running, comparing the maH figure of the car battery with the power of the ICE?

[Erwinseow]

Hello Xiaogary,

 

There is one thing you need to note. OUTPUT POWER of Amps NOT EQUAL to INPUT POWER. Amps have efficiency rating. For ease of use, you can take that your amp have efficiency of 50% (For class AB amps). So if your speaker needs 300W of power. Your amp need 600W of power. Because 50% of the power is lost to heat, etc... So you may need to re-calculate your INPUT fuse.

 

Thanks!

[Xiaogary]

Hi thanks ErwinSeow, I never thot of this. Guess I need to have higher current power supply.

 

Headshok, of course I want to put my sub at home, if not putting sub at home, no kick. The problem is putting sub bcos sub consume super lots of power and jack up the current drawn. The charging of battery can only be possible if it(the charging) is faster than the output. Or else the bass will not be deep or complete.

[Maded]

i wonder if a "hacked" PC power supply will do the job - i have one that churns out 15A on the 12V rail... saw some in SLS that will do 20+A on 12V....

 

Of course, this will have to be connected to a 12V car battery... and probably even some capacitors.....

[Hyun]

can't we use Sensitivity as a way to calculate?

 

say, we want to play music at some 86 or 90 dB.

sensitivity for many speakers is about 86 db / W / m.

are we able to use this formula to estimate power required?

[Kwongwing]

No need to be so complicated lah - check with Slonez, he has a step down transformer which he uses to test car amps on home audio set-ups.

Ask him for the specs of the unit he has lah!!!