# BIG 3, Caps and General Electric stuff



## GaBulldog (Jul 24, 2012)

Seems to be a lot of confusion, Rumors, BS and just plain wrong information out there concerning the car electrical system.
*Big 3 upgrade:* 
Does it help with the dimming of lights, current draw/ recharging rate/discharge rate of the battery etc? Yes and No. 
In the process of "upgrading the ground from the battery to chassis, Ground from Alternator to Battery and the (+) positive Alternator to battery with massive gauge wire" you clean the connectors and ground spots for each termination. Just this action alone will help with the current transfer, the cleaner the connection the less loss due to corrosion. 
The gauge of the wire does determine how much current it is rated to handle. The amount of current in the wire is determined by the output of the Alternator and the Voltage difference across the battery. Not the size of the wire. 
In other words if your battery is a 14.4V cell and the voltage level of the battery is 14 volts the Alternator will be putting out a small current level to ( charge) the battery. If you battery is at 12 volts then your Alternator will be putting out a much larger current to (charge) the battery. 
The current rating for multi-strand wire is dependent on strand size, number of strands, insulation thickness, diameter, cable length and temperature. We will use this example: 
4 Gauge Battery Cable 
Stranding 61/.0250
Nom. Insulation Thickness 0.065”
Nominal O.D. 0.386”
1 ft/ Nominal Temp 200F

The math tells us that this cable will handle 81 amps. 2 Gauge= 120 amps, 0 Gauge =167amps.
Ref: Wire And Cable Derating Criteria From MIL-STD-975

Okay what we see here is that upgrading the wire will give you a greater potential for current flow but if you don’t change the Alternator out you are not increasing the available amount of current.

What people are seeing when they do the BIG 3 upgrade (without an Alternator or Battery change) is a better electrical connection not an increasing the current.

*Capacitors: * 
Do they help your sound system sound better? NO 
Do they help with demands on the cars electrical system? NO
Capacitors are in lay mans terms are quick fire batteries. They store a charge and when the voltage on the circuit they are placed in drops to a certain point they release the stored energy into the circuit. They then recharge and wait for the next voltage drop. The amount of energy they put out is measured in Farads. (I am not going to get into theory here Google it) What you need to know is to get a capacitor big enough to make a difference in your electrical system it would be bigger than most sub boxes. You are better off putting in a second battery. Most if not all but the largest Audio Systems do not need 2 batteries. A HO Alternator and a good battery under the hood are all you need if you are running anything over 1000 watts. 

In summary if you are experiencing dim lights, degraded volume level, amp clipping etc, I would first clean my electrical connections and ensure proper grounding before changing out power cables. Then you need to see what amperage draw you actually have. If it is greater than the output of the alternator then you need a new alternator. If it is within your Alternators output but you are still having problems then I would look at the battery.
There is an exception to this: Cars older than 1995, the electrical systems where not designed with large amperage draws in mind. Newer cars run a lot of electronics hence higher electrical demands. Small cars such as 4 cylinder rides, batteries and not designed to hold large amounts of amperage.

Then of course there is just the cool factor of doing the Big 3 and capacitors, sometimes you just want to have something that looks pretty. (Hence why you buy your wife lingerie)

Just my 5 cents!


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## scott0482 (May 17, 2012)

Yeah, that's pretty much the conclusion I came to 10 years ago.

One thing though. your wire gauge calculations seem off. Those numbers look accurate for about 10-15ft of cable, but big 3 would be much shorter, therefore a smaller gauge wire can handle much more current.

It has been years since I looked any of this up. One, fairly reputable source I could quickly find is crutchfield.

Cable Gauge Chart


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## GaBulldog (Jul 24, 2012)

You are right my calculations are off ( chaulk it up to long days!). The point being that the exsisting factory power wires are more than sufficent to handle the current demands of most audio systems.


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## Hillbilly SQ (Jan 26, 2007)

Agree 100%. The ONLY wiring upgrade I was going to do on my truck was battery to fender but they already did that at the factory with 4g wire. Plus the terminals already had lugs for stacking rings so win win


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## [email protected] (Feb 4, 2008)

I agree that TB3 won't increase the total current available on an average basis, the alternator output capability limits this.

With locally regulated alternators it will provide slightly faster recharging into a suitable battery (AGM / spiral wound) as there will be less voltage drop in the cable at higher currents, and with a higher charging voltage at the terminals the battery will take full output from the alternator for slightly longer. 
It won't help with flooded cells as these recharge much slower.

As you've mentioned cleaning the connections will also be a big contributor to getting the alternator to give it's best too.

With remote sensing alternators it won't make any difference unless the cabling is almost shot. It's only a useful preparation before fitting a bigger alternator in these systems.

With SQ systems the average draw is usually quite low with higher peaks drawn mostly on loud bass notes and transients as the sub takes the lions share of the amp power and therefore current draw. 

Having a power source with stable voltage will help amps with unregulated power supplies to give more power and therefore reduce the chance of clipping. 

The battery won't supply significant current until the terminal voltage drops to around 12.5 so on a big system you could be looking at a fluctuation of 1.5 to 2 volts in the input rails of the amp with the system cranked up. This will drop output power by 25-33% on unregulated amps.

The run of the mill 1 farad caps don't help as they don't store nearly enough energy, though the 15 and particularly the 50 farad Alumapro and similar units will provide short term bursts of curent much higher than the alternator can provide with good voltage stability. 

With the 50F alumapro caps selling for around $500, whether this improvement at higher volume provides value is another issue especially considering a bigger alternator is similar money.


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## jhsellers (Jan 7, 2012)

[email protected] said:


> I agree that TB3 won't increase the total current available on an average basis, the alternator output capability limits this.
> 
> With locally regulated alternators it will provide slightly faster recharging into a suitable battery (AGM / spiral wound) as there will be less voltage drop in the cable at higher currents, and with a higher charging voltage at the terminals the battery will take full output from the alternator for slightly longer.
> It won't help with flooded cells as these recharge much slower.
> ...


Gordon's post is the best synopsis I've seen for vehicle battery/charging circuits, and the strain/limitations placed on them by mobile audio systems. 

Purpose of the Big 3 is not to increase current (or capacity for current flow) - it's to lower the voltage drop that is caused by the current flow through impedance of the conductors. 

Lowered voltage drop in the wiring means more of the system voltage appears at the input of the amplifiers - hence more power available for the speaker outputs. (Potentially, that is - pun intended...) 

Best,
John


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## MAXecutive (Sep 9, 2012)

Excellent post. I'm glad to know that everyone doesn't subscribe to the big 3!!!


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## Joemon (Jul 9, 2010)

always good to change factory wires for good current flow and for future upgrades also. and its cheap and easy to do


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## Laramy-Audio (Oct 25, 2012)

Capacitors do nothing to increase steady current flow, if you have a 100A alternator, 100A is all you can hope for over the long haul, and in reality you will have less due to other parts of the car drawing power. Where the big cap comes in to play is transient current. That big kick drum pulse can draw current higher than the alternator/battery can supply, but the cap can use it's stored energy to deliver the current spike needed for transient response. This is why good home audio amps have huge capacitor banks in their power supplies. For best results, mount the cap as close to your amp as possible to minimize I2R losses.


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## RNBRAD (Oct 30, 2012)

Laramy-Audio said:


> Capacitors do nothing to increase steady current flow, if you have a 100A alternator, 100A is all you can hope for over the long haul, and in reality you will have less due to other parts of the car drawing power. Where the big cap comes in to play is transient current. That big kick drum pulse can draw current higher than the alternator/battery can supply, but the cap can use it's stored energy to deliver the current spike needed for transient response. This is why good home audio amps have huge capacitor banks in their power supplies. For best results, mount the cap as close to your amp as possible to minimize I2R losses.


Good points. It's obvious that the location of the caps is crucial to their benefit. That's why in a car with amps a good clip from the batteries, a cap can be more benificial and audibly so. Many variables come into play but I feel that distance/time is most significant.


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