voltage drop problem, what battery to buy?

oldspark wrote: You use you voltmeter or multimeter to find your biggest voltage drop - eg: * in the ground circuit: chassis to engine block; battery- to chassis or engine; chassis (or whatever) to the amps. * in the power circuit: alternator to battery+; battery+ to front/nearby fuse or distro block; across fuse/distro; distro to amps (or front fuse to rear distro; across distro; distro to each amp/load) etc. IE - find the voltage drop across each section. Tackle the biggest drop first. Doubling your copper (cable) across that section will halve that voltage drop. That's your cheapest option. And reducing that 1.5V drop is VERY worthwhile. (That's 150W lost per 100 Amps of load.) You might then consider boosting your source voltage from about 12.7V to 13.8-14.4V with a bigger alternator.

So here is the REVISED scoop. I went out and got a 320A Iraggi Alternator. I also changed the amps up from Sundown SAZ1500D's and SAX50.4 to Cadence Audio C9 and C5. The subs will now be wired for a 2 ohm load at the amp instead of 3/4, so this should be way more stable. The C9 will also put out more power than the SAZ1500D at 2 Ohms simply because it is a bigger amp (physically) and it is rated higher. The amps are wired like so: Battery (+ and -) ---> C9 ---> C5 So essentially there is a direct Voltage line from the positive terminal of the battery to the +12V terminal on the C9 and a direct ground from the negative terminal to the C9's GND terminal (0 GA on both lines). From there, an 8 gauge wire was inserted in the power and ground terminals on the C9 and it was ran to the C5's +12V and GND terminals (respectively). These lines act like "jumpers". According to one of the engineers at Cadence, the amplifiers need at least 11V to operate safely. My questions include the following: 1. Will my STOCK battery be able to run this entire system now that I have the tremendous charging upgrade or is there just not enough capacity there for the battery to provide power? 2. Someone was telling me I should establish a common "ground plane" between the head unit and the amplifiers considering the distance between them. Is this a valid point? He was saying I should run a small jumper line from the C5 (4 channel small amp) to the head units + and GND inputs on the back, then it all would be hooked up to the same voltage and ground plane. Does this make any sense? To be more explicit, he said that I would run a 20 ga wire in the + input on the C9 (which is being fed by an 8 gaug + input jumper from the C5) and run it to the + input on the head unit, and do the same with the negative for the GND terminals. Please let me know what your thoughts are.

The battery will provide enough power until it discharges to the point where - with voltage drops - the amp sees 11V. I don't know how else to answer that part of your question....

oldspark wrote: The battery will provide enough power until it discharges to the point where - with voltage drops - the amp sees 11V. I don't know how else to answer that part of your question....

Well I had asked a few questions in there, and nobody has responded about the whole grounding plane idea. At any rate, would my battery sustain that 13.8-12V charge considering how fast the alternator is recharging it?

The ground plane depends what it is there for. An antenna's radiation? A common ground to avoid ground loops? If there is no need for it, then why have an extra connection point hence more resistance etc in the paths? The battery does not sustain 13.8V etc. Excluding surface charge, a fully charged battery can only supply (sustain?) up to ~12.7V. It is the alternator that sustains the load above the battery's voltage (eg, max 12.7V). Below 12.7, it is the battery and whatever the alternator is supplying. So however long your battery can sustain your load without the alternator is the minimum time the battery will sustain the load with the alternator. Does that make sense? The battery sustains the load until it is discharged - ie, ~12.4V for cranking batteries, ~11.6V or lower for deep cycle. (Those are internal cell voltages - ie, without the internal-resistance voltage drops. This may mean 11.4 or 10.4 or 9.4V at the terminals under load.) But your load will probably hit 11V before the battery is discharged.

oldspark wrote: The ground plane depends what it is there for. An antenna's radiation? A common ground to avoid ground loops? If there is no need for it, then why have an extra connection point hence more resistance etc in the paths? The battery does not sustain 13.8V etc. Excluding surface charge, a fully charged battery can only supply (sustain?) up to ~12.7V. It is the alternator that sustains the load above the battery's voltage (eg, max 12.7V). Below 12.7, it is the battery and whatever the alternator is supplying. So however long your battery can sustain your load without the alternator is the minimum time the battery will sustain the load with the alternator. Does that make sense? The battery sustains the load until it is discharged - ie, ~12.4V for cranking batteries, ~11.6V or lower for deep cycle. (Those are internal cell voltages - ie, without the internal-resistance voltage drops. This may mean 11.4 or 10.4 or 9.4V at the terminals under load.) But your load will probably hit 11V before the battery is discharged.

So are you saying that when I'm driving and listening to my music that there could be a point where my battery runs out of potential and cannot sustain the load despite my alternator charging? Also, do you surmise that there would be sufficient voltage fluctuation to possibly fry the connected equipment? What I mean from GND plane is establishing a common 12V and GND signal from the amplifiers and the head unit. Is this a good idea by running the + and - wires for my head unit as jumpers from my 4 channel + and - ports?

LOL! We are going in circles again!

michigan_tech wrote: So are you saying that when I'm driving and listening to my music that there could be a point where my battery runs out of potential and cannot sustain the load despite my alternator charging?

No - you are suggesting that your alternator cannot always supply the load. You are hence discharging your battery.

michigan_tech wrote: Also, do you surmise that there would be sufficient voltage fluctuation to possibly fry the connected equipment?

No - I am not familiar with the equipment. (You mentioned 11V etc.)

michigan_tech wrote: What I mean from GND plane is establishing a common 12V and GND signal from the amplifiers and the head unit. Is this a good idea by running the + and - wires for my head unit as jumpers from my 4 channel + and - ports?

IE - a common ground, or ground bus etc. Though I see reason for common ground point, I see no reason to introduce another one. What is wrong with the common point between the battery & body? (Or alternator/engine if you prefer?)    But irrespective of the commonality, as KLF wrote ((klferguson26; and just before 3AM too LOL!), you will have voltage drops to or from it. You can minimise the drops. And they may NOT matter anyhow. (The common +12V is lesser issue since things are not referenced to it the same way as ground - ie, ground loops, not hot or +12V loops.) I'm merely (re-)stating the basics. Re-read the thread (or my replies) if you don't understand that we are repeating the same. EG - when the alternator can't supply the load, the battery discharges. How long till it flattens? Refer to battery specs and discharge curves for your load (else approximate through AH ratings).

In general, can voltage fluctuation between 10 - 12 Volts damage amplifiers even if they are stable at nearly 10 V?

michigan_tech wrote: In general, can voltage fluctuation between 10 - 12 Volts damage amplifiers even if they are stable at nearly 10 V?

The voltage is barely fluctuating at all now! I just hooked it all up, established common V and GND between the head unit and the amps, and I get about 14.3 V at the battery and 14.0 at the amps, and thats running it 3/4 of the way up! I peaked it out with 13.8V at battery and 13.5V at the amps, so very efficient so it seems! No heating problems from the amplifiers!