do i need a battery isolator?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=92615
Printed Date: April 27, 2024 at 1:04 AM
Topic: do i need a battery isolator?
Posted By: mbaudio06
Subject: do i need a battery isolator?
Date Posted: April 06, 2007 at 4:25 PM
I havent decided on how many batteries to run yet. I have a Crossfire VR2400D amp with 2 XT212s. I open the box of the amp and it says i need at least two batteries to run this bitch. No can i just run one optima up front and an optima in the back, will that count as two batteries? Or do i need to run two seperate batteries in the back for the amp? Also i know if i want to play my car when the engine isnt running I need a battery isolator. Could i just hook up the batteries inline together with 0guage and be done with it?
Replies:
Posted By: Velocity Motors
Date Posted: April 06, 2007 at 8:21 PM
This was taken from a site on outboard electronics:
Let's dispel the myths of multiple battery charging sources.
All a battery charger sees on the 12 volt circuit is a voltage.
It has no "knowledge" of what else is on there, charging or discharging.
It just responds to the voltage it sees at any one time.
1. If it is a dumb regulator or charger and the battery voltage it sees is less than its built in threshold, it charges at full strength governed by the difference between its internal voltage/source impedance and the actual battery voltage. When the voltage rises to the threshold, it stops charging. This process my cycle on and off at different speeds depending on loads, etc.
2. If it is a smart alternator or charger, then the above scenario is complicated by having multiple threshold voltages at which it changes from full charge to topping-off charge to maintenance charge, to off, however the underlying principle is the same. There may also be timers and temperature inputs that modify the thresholds.
So what happens when there is more than one charging source is all those regulators that see a voltage less than the (next) threshold, charge the battery as though the other charging sources weren't there. They don't "know" anything else is charging. During the bulk charge, when the battery voltage is below all the thresholds, all the sources will be putting out the maximum they can. As each charging source reaches a threshold it changes its charging rate accordingly. Since no two regulators will have exactly the same threshold(s) this means that some of the paralleled regulators will tend to cut down or shut down before others and leave the job of finishing the charge to them but by that stage the current requirements are within the capacity of the one(s) that continue(s) to remain on line.
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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
Posted By: haemphyst
Date Posted: April 07, 2007 at 6:36 PM
That's great, Jeff, but wth??? Even *I* was confused by that...  ------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: omzig10
Date Posted: June 05, 2007 at 7:56 PM
Um... So did anyone every answer this question? I'm trying to figure out if the shop trys to sell me an isolator for my setup if it's necessary as well... Omzig10
Posted By: j_darling2007
Date Posted: June 05, 2007 at 10:35 PM
It takes power to make power. Batteries just store the power made by the alternator. If you don't plan on running the system with the vehicle off, you really don't need an extra battery in my opinion. You should put that money towards a high output alternator. An extra battery can't really hurt, though, as long as your alternator is strong enough to make the power to feed the amplifier.
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There are 3 kinds of people in the world, those who can count and those who can't
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