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    Re: Rear batt voltage drop when amps are on

    Quote Originally Posted by Xprime4 View Post
    so, i wouldn't need to ground the rear batt on chasis if i had all my amp ground on the neg of that batt

    i'll put my dash voltmeter on my back batt, so i'll monitor the drop better with car off. Considering that once the amps power on, i'm down to 11.7ish, what should be my maximum drop to keep it safe? not under 11v i guess, but i would like your opinion Loopkiller

    btw, you should be the moderator of this wiring and electrical forum.

    also, bassracers must burn few amps per year with low voltage?
    You have to remember that the source of your power on the POS+ is also your end point for your NEG- side. So the electrons flow down the POS+ wire, through your amp, and then they must get back to the NEG- post of that same power source. The shorter that route, the better. So if your amps are powered by the rear battery with the engine off, then you want the NEG- wire for the amps going directly to the NEG- on the rear battery.

    But, when you have the car on, the alt is going to be making power too. So your grounds then have to send the electrons back to the NEG- of your alt. The NEG- of the alt is the outside metal of the alt, which is connected to the engine block, which should be connected to the chassis. That is why you would normally ground your amp to the chassis, so it could be connected to the metal of the alt.

    The problem with using the chassis as your connection back to the NEG- of the alt is that steel is a poor conductor and even worse when 20 pieces are welded together. That is why bigger systems need a dedicated wire for your grounds.

    As for the mod comment, I appreciate your flattering comments, but I am just here to help and am not looking for added responsibilities.

    Quote Originally Posted by Xprime4 View Post
    also , once the amp caps are charged, should my "iddle"battery voltage goes up? I just check today and i was around 11.70 with music playing at confortable level.
    Yes, I would expect that when you first turn on the HU, the amps will then power up, and at that time you will see a dip in voltage. But if you are not playing at a high volume, the current draw will taper off and you should expect the battery voltages to come back up.

    Also, when batteries have not been used for a period of time, they become somewhat dormant. After the initial draw, they will begin to make more power for a short term. If you had a load tester and you loaded a dormant battery to a given amperage, say 200A, then watched the voltage, you would see the immediate drop in voltage from the resting voltage. Let's say it rested at 12.8V and the 200A load initially dropped it to 11.8V. You would then start to see the voltage gradually climb back, let's to say 12.1V and hold steady, even under the same 200A load. Now this will only hold true while the battery still has plenty of reserve power. After some time, you again would see the battery start dropping in voltage again as the battery was drained. This amount of time would be determined by the battery's capacity.







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    Re: Rear batt voltage drop when amps are on

    Quote Originally Posted by loopkiller View Post
    You have to remember that the source of your power on the POS+ is also your end point for your NEG- side. So the electrons flow down the POS+ wire, through your amp, and then they must get back to the NEG- post of that same power source. The shorter that route, the better. So if your amps are powered by the rear battery with the engine off, then you want the NEG- wire for the amps going directly to the NEG- on the rear battery.

    But, when you have the car on, the alt is going to be making power too. So your grounds then have to send the electrons back to the NEG- of your alt. The NEG- of the alt is the outside metal of the alt, which is connected to the engine block, which should be connected to the chassis. That is why you would normally ground your amp to the chassis, so it could be connected to the metal of the alt.

    The problem with using the chassis as your connection back to the NEG- of the alt is that steel is a poor conductor and even worse when 20 pieces are welded together. That is why bigger systems need a dedicated wire for your grounds.

    As for the mod comment, I appreciate your flattering comments, but I am just here to help and am not looking for added responsibilities.



    Yes, I would expect that when you first turn on the HU, the amps will then power up, and at that time you will see a dip in voltage. But if you are not playing at a high volume, the current draw will taper off and you should expect the battery voltages to come back up.

    Also, when batteries have not been used for a period of time, they become somewhat dormant. After the initial draw, they will begin to make more power for a short term. If you had a load tester and you loaded a dormant battery to a given amperage, say 200A, then watched the voltage, you would see the immediate drop in voltage from the resting voltage. Let's say it rested at 12.8V and the 200A load initially dropped it to 11.8V. You would then start to see the voltage gradually climb back, let's to say 12.1V and hold steady, even under the same 200A load. Now this will only hold true while the battery still has plenty of reserve power. After some time, you again would see the battery start dropping in voltage again as the battery was drained. This amount of time would be determined by the battery's capacity.

    so much clearer thank you. So I don't have to worry about that too much then. I'll be swapping car soon, and on my next setup, i'll make sure i get back to the alty neg.
    Also, what should be my minumum voltage for safe listening?




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    Re: Rear batt voltage drop when amps are on

    Quote Originally Posted by Xprime4 View Post
    so much clearer thank you. So I don't have to worry about that too much then. I'll be swapping car soon, and on my next setup, i'll make sure i get back to the alty neg.
    Also, what should be my minumum voltage for safe listening?
    I would say the higher the better, but absolutely not below 11.0V.




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    Re: Rear batt voltage drop when amps are on

    Quote Originally Posted by loopkiller View Post
    I would say the higher the better, but absolutely not below 11.0V.
    ok. i'll aim for that




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