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Old 09-24-2020, 11:23 AM   #1
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Adding a second 12v battery?

I have a champion inverter 3500watt. I have a single 12v deep cycle battery wired into the TT electrical system and I suppose to the TT inverter. Is there a benefit to adding a second 12v deep cycle to the system? Added capacity?

I know if I add solar I need storage capacity. Probably not adding solar to this TT. when we upgrade to a 5th wheel it will probably have a pretty deep solar setup. lots of cells and lots of Lithium battery and a huge inverter/controller. But that is a while off.

So is there any real reason to add another lead acid/AGM deep cycle and if there is how would one go about wiring it into the system? Diagram? Parallel? Series?

Ya'll aint steered me wrong yet, Thanks.
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Old 09-24-2020, 11:40 AM   #2
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It depends in your needs if you should add more batteries.

If you make it thru the non generator times, you fine.

If you wake up to no fridge power, add one 12 volt in parallel.

Before you add another battery, make sure the one your adding to is good. If its over a year old and been run down many times, buy 2 new ones, trading in the used one.
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Old 09-28-2020, 05:51 PM   #3
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Some prefer to buy a battery monitor first. Then they know exactly how much battery ah they need.
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Old 09-28-2020, 09:38 PM   #4
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if you are going to have two batteries, use two big 6v batteries in series. MUCH better than 12's in parallel
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Old 09-29-2020, 06:19 AM   #5
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Quote:
Originally Posted by VanDiemen23 View Post
if you are going to have two batteries, use two big 6v batteries in series. MUCH better than 12's in parallel
Very true if FLA
AGMs are not the same and there are many more good options for parallel 12V that provide good deep cycle (and start) performance.
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Old 09-29-2020, 06:41 AM   #6
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2nd the battery monitor. Without a good understanding of power requirements, you're just guessing. The more you know, the better decision you'll be able to make.

Understand that you're dealing with a system. If you add a battery, you'll need to assess how that change impacts the rest of the system. With more battery capacity, comes the need to insure that the cabling infrastructure is adequate, that you can fully charge the bank, that it's properly fused, etc. Failure to consider all aspects of a change may limit the effectiveness of the entire system.

If you plan to add capacity, replace the battery with new ones that are matched and the same age, and make sure the cabling and fusing are appropriate. Match the battery bank capacity to your consumption/needs. Mismatched batteries in a bank result in uneven charging and may lead to premature failure of the batteries. New/old batteries have different charging profiles, so components of the bank should always be matched by capacity, birthdate, manufacturer, etc.
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Old 09-29-2020, 06:56 AM   #7
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Originally Posted by VanDiemen23 View Post
if you are going to have two batteries, use two big 6v batteries in series. MUCH better than 12's in parallel
First time I have heard this... why is that?

Why would there be any difference?
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Old 09-29-2020, 09:21 AM   #8
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First time I have heard this... why is that?

Why would there be any difference?
Here is the reason for FLA - but beware it's not the same for AGM

https://marinehowto.com/what-is-a-deep-cycle-battery/
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Old 09-29-2020, 12:20 PM   #9
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The issue with putting 2 6v batteries creating a 12 v system, is that the max amperage you will get is the max of 1 6 v battery. I.E. 2 6v 150 amp hour batteries will get you 150 amp hours, period. If you install 2 12v 150 amp hour batteries, you will get 300 amp hours.
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Old 09-29-2020, 12:52 PM   #10
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The issue with putting 2 6v batteries creating a 12 v system, is that the max amperage you will get is the max of 1 6 v battery. I.E. 2 6v 150 amp hour batteries will get you 150 amp hours, period. If you install 2 12v 150 amp hour batteries, you will get 300 amp hours.
True.... however those 6V GCs AH are roughly 2X a typical 12V batty... so no free lunch. The benefit of 6V GCs is they are a high volume item designed for rough service and many deep cycles hence longer life and great performance.... so very cost effective.

6V GC roughly 200-220 AH so 2 = 200AH at 12V

12V battys roughly 100-105AH so 2= 200AH at 12V

Even 12V Marine / RV battys are not true deep cycle like GCs.
Your $.... your choice!
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Old 09-29-2020, 12:54 PM   #11
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6 volt golf cart batteries will hold more amp hours compared to 12 volt batteries of similar size because the 6 volt batteries have only 3 cell dividers compared to a 12 volt batteries six cell dividers. Each cell produces 2.1 volts in both 6 and 12 volt batteries. Cell dividers only take space while producing no voltage. A 6 battery is also a true deep cycle battery because of their intended use to power either an electric golf cart or electric fork lift. 12 volt batteries are starting batteries only regardless of what they say on the battery itself. This is purely marketing to their intended target audience. 6 volt batteries are clearly intended towards the industrial market and 12 volt batteries to the automobile consumer market. The manufacturer of the battery just offers different warranties on the same made batteries whether they are a starting battery VS a deep cycle battery and this is verified by disassembling the batteries for inspection.
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