Questions about dual battery install

I finally got around to getting my dual battery installed and noticed a few things I want to understand further / confirm:

- it seems that the battery that i added for stereo usage may be on the downside of life and only showing 12.2 volts (via my little digital meter) where my starter is newer and in better shape at 13.2 volts.......the day after the install I noticed that the batteries are now both showing around the 12.2-12.6 range so my question: could the stereo battery be pulling down the performance of my starting battery??

- if my stereo battery is indeed on its last legs and needs to be replaced, what would be my best low-cost option to replace it?

- i'm using these voltage gauges (https://www.amazon.com/dp/B00YALV0NG...v_ov_lig_dp_it) on each of the batteries and hooked DIRECTLY to each battery and always on.......is this is a bad idea that may cause the batteries to drain too quickly?

How do you have them hooked up? Are you using a perko switch or ACH? Need some more info to figure out the draw issue.

12.2-12.6V is typical if they aren’t seeing any charge from the alternator.


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Originally Posted by mikenehrkorn

- if my stereo battery is indeed on its last legs and needs to be replaced, what would be my best low-cost option to replace it?

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Lots of options on batteries, not sure what size you are running 24, 27, etc, low cost options would be found at CostCo, WalMart, or Sams.

A few things first. You need to verify that the dual bank setup is operating correctly. This would be confirmed with a known good digital volt/ohm multi-meter. You want to test for alternator charge to both battery banks, when its supposed to be there.

Next, what is the static (at rest) voltage and engine running voltage, of both batteries? If the static voltage is low, then you first need to attempt to charge the battery. Then let the surface charge dissipate, then remeasure voltage. You let the freshly charged battery sit for a few hours, or depending on your switch setup, do 2 to 3 10 second cranks of the engine. Or turn the stereo on for about 15-20 minutes. a good used battery should rest at at least 12.5V.

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Three-Wire Calibratable DC 0~30V Blue Digital Mini Voltmeter Gauge Tester

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This is an instant red flag for me. For testing, you need to be sure your equipment is not lying to you.

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Originally Posted by Branden967

How do you have them hooked up? Are you using a perko switch or ACH? Need some more info to figure out the draw issue.

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Using a Blue Sea battery switch (https://www.amazon.com/Blue-Sea-9001...g-goods&sr=1-2)

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Originally Posted by MLA

A few things first. You need to verify that the dual bank setup is operating correctly. This would be confirmed with a known good digital volt/ohm multi-meter. You want to test for alternator charge to both battery banks, when its supposed to be there.

Next, what is the static (at rest) voltage and engine running voltage, of both batteries? If the static voltage is low, then you first need to attempt to charge the battery. Then let the surface charge dissipate, then remeasure voltage. You let the freshly charged battery sit for a few hours, or depending on your switch setup, do 2 to 3 10 second cranks of the engine. Or turn the stereo on for about 15-20 minutes. a good used battery should rest at at least 12.5V.



This is an instant red flag for me. For testing, you need to be sure your equipment is not lying to you.

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Not near the batteries right now, but will do those tests and report back what I find