Capacitor

C

Chippy657

Torque Junkie
Points
62
Location
Gosport, England
Car
Peugeot 206 LX
Right another question from me (shock)

I have installed my sub and such and when i have the engine running and the lights on they start to flicker when the sub kicks in, i know i need a capacitor but not sure what farad i need.

I have this sub running of this amp, it is bridged so any ideas?

hope thats all the info you need!!!
 
I'd be checking all the wiring to the amp before investing in a Power Cap. 900 watts peak shouldn't really affect the lights on the car unless the battery and alternator are weak. Make sure you have a good short earth cable. The shorter the earth cable the better. Bad connections will make your lights dim but you may well just need to reinstall the system with better quality cable.
 
So a 1 farad capacitor will be sufficient for what i need and thanks for the replies

Turbonutter- My earth cable is only 15cm long, my connections are all very good and i have a Juice wiring kit so the quality should be there. I understand what you are saying about bad connections because i come across them all the time in my day job!

p.s. Is juice any good? i have heard thay are but just need an experienced opinion!!!
 
dont know mate, i allways mad my own wiring kits much cheaper.
could be the altinator is unable to produce enough power. not going to be running full whack but even at 500w thats still 42amps if youve got lights etc on it could be pulling too much.
what size altinators on it?
 
the thing that charges the battery. basically a generator that is turned by belt, along with the regulator ( most are inbuilt to the alternator) it provides around 13-14v constant to provide power for the car and recharge the battery

follow the power lead on the battery there should be 2. one leads to the fuse box the other should go to the alternator.
 
HDi fun said:
900 watts is about 75 amps load at 12 volts!!
Click to expand...

I had a 1200 watt D-class amp running 2 12 inch subs and the amp was running at 1ohm stable which boosted the amps power to 2400 watts. I didn't need the capacitor but I bought it so the bass stayed strong however loud it is played. A 900 watt amp should not make the light's flicker. What engine is in the car?
Juice are a good name but there is better out there.
 
Engine is only a 1.2

I must have explained wrong, when the sub is on and a really demanding part comes in (not very often but enough to annoy me) the headlights dim ever so slightly.

Also another question, when i was setting up the amp and sub, setting the gain
and all that, i must have had the system on for 20-30 mins and then i couldnt start the engine afterwards the battery had died, i charged the battery and everything was fine, so would a capacitor allow me to play music with the engine off and still be able to start the car afterwards?

Cheers pgarner i found the alternator so i learned one thing today.
 
The battery itself will take over when the alternator can't deliver enough current. Perhaps the battery itself is in need of replacement if lights are dimming slightly. If its internal resistance is going up, as is typical when a battery failing then this is a likely symptom.


CLASS D AMPLIFIERS

CLASS D AMPLIFIERS are not linear devices. They operate the output devices (whether BJTs or MOSFETs) in switched mode. This ensures that the devices are either fully on fully off, thereby increasing efficiency as there is no partial conduction.

Despite the fact that semiconductors don't obey Ohm's law all the time they do so fairly well when operated in their linear region. As such, the source and load see the output device as a simple resistance. And the same rules apply as to simple resistors ie Power (WATTS)=I x I x R.

This power is dissipated as heat within the output device and makes NO contribution whatsoever to the signal output power.

Class D amplifiers rely heavily upon low pass filtering before driving the final load in order to get rid of quantization noise. They are not necessarily of high audio quality and their frequency response is highly dependent upon the impedance of the final load.

A later development is the CLASS H amplifier. In this arrangement the amps supply rails' voltages themselves are continuously modulated to ensure that the output devices foward current can nearly always be at maximum. These, too, rely upon LPF networks for driving a loudspeaker.

Impedance is nowhere near as straightfoward as simple resistance. as such, the linearity of frequency response from a switched mode amplifier can be quite poor.
 
I understand what your saying there HDI. But an you knew there was gonna be a but Class D amps where developed for driving subwoofers. A class d amp will deliver the power a hell of alot better and stronger than your normal Mosfet amp. I know the class d is more efficient than a standard mosfet but mine was delivering 2400 watts of pure bass and didn't affect the lights at all. But in a 1.2 it may well be that because i'd emagine that a 2.0 litre engine has a more powerfull battery and alternator than a 1.2 .
And yes Chippy you would be able to have the stereo on and the battery should be fine. But it will drain eventually if say constant all day with the engine switched off.
 
mmm going to diagree there TN
the capacitor is basically a small battery just with lower resistance, this is why it can discharge itself quicker than the main battery when alot of current is required. the battery will basically die just as quick.

chippy did you look closely at the altinator ? it should have had a rating on it somewhere. on a 1.2 i wouldnt be looking high it might only be 60 amp compared to 120amp on a bigger engine
 
I doubt the 2400 watts claim, That's over 200 amps at 12 volts. Class D amplifiers are more efficient that linear amplifiers but even so you can never get more than you put in.
 
The capacitor will hold alot of charge when the ignotion is off. Please just trust me on this 1. Before I had the cap I needed the engine running to turn up the volume as the amps where drawing that much power the stereo kept switching itself off. Now with the cap installed I can sit without the engine running and crank up the volume without the stereo cutting out. No it won't last forever but will last longer than a battery on it's own. Plus the fact that the caps readout will tell if the power levels are dropping then just restart the engine before it's drained.
As far as 2400 watts. This is a true power figure as it is setup to run at 1 ohm stable. (it may be 2ohm but i'll check and then update but i'm sure it's 1 ohm) I don't know how to explain but in lamen terms the lower the ohms the more power an amplfier can produce. I'll try an find some info for you. But my amp is now running 2400 watts of pure Bass and this is fact!
 
turbonutter69 said:
The capacitor will hold alot of charge when the ignotion is off. Please just trust me on this 1. Before I had the cap I needed the engine running to turn up the volume as the amps where drawing that much power the stereo kept switching itself off. Now with the cap installed I can sit without the engine running and crank up the volume without the stereo cutting out. No it won't last forever but will last longer than a battery on it's own. Plus the fact that the caps readout will tell if the power levels are dropping then just restart the engine before it's drained.
Click to expand...

correct to a point, i had the same problem my HU would flash without the cap when i had something with alot of bass in it. after installing the cap it never did it again. this was due to the cap being able to supply the current quickly. the battery didnt last any longer however after around 50mins that was it had to restart the car. i had a low battery alarm that sounded when the battery dropped below 11v
 
Cheers for all your help!

pgarner i didnt look that closely but your probably right about the 60 amp thing although my amp cannot take more than 40A due to the inline fuse.

I am going to invest in a capacitor even if it has no affect on the headlights dimming ever so slightly, it will put my mind at rest knowing i can have my music on for 10 minutes and know that i will be able to start the car afterwards!!!
 
you should be able to have it on for 10 mins without any problem.
if your going to be parked up blaring for a while look at installing another battery in the boot and power the amp off this. to charge it get an split charger

the cheap split chargers use a relay that connects to the ignition when the engines on the relay is closed and the latinator charges both battery. when the engines switched off the relay is open so it just uses the spare battery.
just make sure you go for a gel battery incase the worst happens
 
pgarner said:
you should be able to have it on for 10 mins without any problem.
if your going to be parked up blaring for a while look at installing another battery in the boot and power the amp off this. to charge it get an split charger

the cheap split chargers use a relay that connects to the ignition when the engines on the relay is closed and the latinator charges both battery. when the engines switched off the relay is open so it just uses the spare battery.
just make sure you go for a gel battery incase the worst happens
Click to expand...

I understand multiple batteries being installed when there is say a MTX Jackhammer that needs that kind of juice. But for a simple install a power cap will suffice. I have a 2 Farad power cap and it will last longer than 50 minutes without the engine running.
 
im just suggesting it as it sounds like his standard battery is rather small. and maybe insuficiant at delivering enough juice for a lengh of time yours might be alot larger. the prelude used to run for around an hr before the alarm would sound with system and TV running, that was with a 1 , might have been 1.5 cant honestly remember, farad cap. where as the boras battery is alot smaller. i get around half and hour to 40 mins with the carputer and HU with standard speakers no amps at all before it switches itself off (low voltage on the power supply kills power when the battery drops below 11.5v) simply because the battery is smaller rated

chippy look at your battery and see what the rating on it is
look for XX Ahr.
 
He wouldn't need a seperate battery even if his is weak. Just upgrade the current battery in the car and then add the power cap and everything should be fine. How old is the car? Some on the earths may need replacing.
Understand where your coming from Pgarner buddy but IMO it's just too much work when all is needed is to possibly upgrade the current battery and install the cap.
 
no worries mate, i was needing mine to run for a couple of hours at a time so had a second battery wired in this way as it was the easist way of doing it. already had decent wiring to the amp so removed it and fitted the battery with an isolater up front then ran a short earth wire from the 2nd battery.

depends if theres room for a decent battery. ive no idea how big the battery tray is in the 206. if he can get a dcent one in then yup it wont be a problem, a new one might not be much better if the current ones in good nick, but if he cant.. then he can get back in touch
 
yeah thats more or less what i was on about installing in the back. the battery box of the 206 looks like its stuck in, so really need the sizes of the battery to see if a better one can be fitted
 
Wow i caused a bit of a debate lol.

havent had the chance to look at my battery yet will do soon, i am going to get a capacitor anyway and just go with that, im to lazy to wire in another battery or think of any other solutions , the capacitor seems easiest so im going with that!
 
Chippy657 said:
Wow i caused a bit of a debate lol.

havent had the chance to look at my battery yet will do soon, i am going to get a capacitor anyway and just go with that, im to lazy to wire in another battery or think of any other solutions , the capacitor seems easiest so im going with that!
Click to expand...

I like a good debate...:D
Power Cap will do you fine buddy.
 
Yeah thats the basic jist of a power cap. It just delivers the power quicker.
If I was Chippy though I'd spend a few extra pennies and get a 2 farad cap. So there is then scope for adding more amps in the future. ;)
 
A power cap doesn't deliver current any more quickly than a battery mounted very close to the power amp's supply input. Caps and batteries are one and the same. Both rely upon electrolysis in their operation.
 
Would it be worth opening the power amp and fitting caps between the amps supply rails and 0v downstream of the inverter? A 70 volt cap could be of a much smaller capacity (farads).

It would be much smaller in size. You'd also not have to wait for the latency of the inverter which itself can cause poor transient response.
 
mmm.. not sure about that, been a while since i played about with amplifers in the classroom so cant remember how they are set up.
makes sense in the delay time and the size as the voltage is higher the current would be lower
 
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