battery question
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=61770
Printed Date: July 05, 2025 at 5:42 AM
Topic: battery question
Posted By: choover567
Subject: battery question
Date Posted: August 21, 2005 at 2:29 AM
would it be a bad idea to run my yellowcap optima battery off of my regular car battery in the front? then off the optima battery ill be running my amp and such? strait pos wire from regular batt to the optima batt... and grounded in different places, good or bad idea?
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Chris - 97 Toyota 4Runner
Alpine CDA-9884
Kicker SX1250.1
Kicker 15" L7
Replies:
Posted By: Velocity Motors
Date Posted: August 21, 2005 at 10:05 AM
Some say it's not a good idea to run two different batteries for a dual battery set up. If you do, make sure you purcahse a battery isolator otherwise you will run into problems with charging. The ground doesn't matter if it's in two different places, but just ensure you meter the battery in the back for a grounding location that is as close to absolute 0 as possible. ------------- Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
Posted By: haemphyst
Date Posted: August 21, 2005 at 1:15 PM
It's not a charging issue, but a DIScharging issue. When the car is off, one battery will have a lower internal impedance, and this one will cause the other battery to discharge through it - it will remain fully charged - and the other will slowly collapse. Lead-acid batteries do not like being discharged to deep states, and so one of the batteries will die FAR sooner than the other.
If you are wanting to do this, consider how old the battery in front is, and if it is probably getting ready to be replaced soon anyway. Replace it with an identical battery (another SAME MODEL yellow-top) and you will avoid the need for isolators and what-nots like that.
Everything else Jeff told you... Its right on. Good grounds are essential!
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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: choover567
Date Posted: August 22, 2005 at 12:24 AM
so if i got two optima batteries then... one for my car... ran a pos wire from that battery back to my second optima battery... good grounding... no problem? or still gonna need an "isolator" what is that anyway? sry im a battery newb
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Chris - 97 Toyota 4Runner
Alpine CDA-9884
Kicker SX1250.1
Kicker 15" L7
Posted By: haemphyst
Date Posted: August 22, 2005 at 6:01 PM
Yes, you are absolutely correct. Since you won't need an isolator, you won't really need to worry about what they do, but they are simply diodes or relays that allow the alternator to "see" both batteries during charging, but will not allow the batteries to "see" each other. They "isolate" one from the other, allowing one to power your stereo, without the other doing the same. I HIGHLY and COMPLETELY recommend against them, but others highly recommend FOR them...
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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."
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