Our camper has only room for one group 24 battery. A few years ago I added wiring and a multipoint switch for an additional battery to go ahead of the rear wheel well but have not used it until now.My questions relates to the second battery. If I add a second group 24 do I also have to replace my current battery to keep them the same age? Would it be worth it to add a group 27 or 31 to maximize my storage capacity? This would require switching from one bank to another and I wonder if it is more trouble than it is worth.Your thoughts please.

Hard to give a good answer without more information.If the "old" battery is more than 3 years old and/or has been run WAY down more than once, I think it should be replaced too.No need to separate two batteries into "banks" unless one is a LOT bigger than the other. Two the same in parallel is the most common arrangement in a situation like yours. Unless you got real fancy with the cables, the added one will tend to discharge and recharge slower because of the cable lengths.

From my experience batteries of different age might mess each other only if left connected in storage for long time. When you constantly use/recharge the batteries, you always use both regardless minimal differences in voltage. I run dual batteries in several vehicles and even batteries bought together, having the same manufacture date can show 0.1V difference.In my boating years I had my travel trailer in storage close to the lake. With no hookups, I was taking trailer battery home for recharging, but for emergency brakes and short run of water pump I put old motorcycle battery in it. The recharged big battery would connect with alligator clips to much smaller and much older battery and work whole weekend just fine.

Everyone has always told me that the batteries should be the same age. However, I think you have another issue because they are some distance apart. I think I would consider another switch and charge them separately and run them separately as well. I don't know why you are needing the second battery, but if you haven't switched to LEDs, you probably should.Finally, I'd measure the compartment and potential batteries. All Group 24, 27s, etc aren't exactly the same size and they also are different amp rated as well.

My Lance had a compartment for one battery. The first battery was an Optima, I went through three of those over a three year period. They just went bad. I put in a group 31 AGM in year four, I think. Then I added a second battery under the wing of the TC. I used 8ft of marine gauge no 4 cable with an Anderson connection. I ran this set up for about six year without a problem. Last year the older battery went bad so I bought two new ones.The point being the battery's were not the same age nor manufacture and I got good service from my set up.

jimh425 wrote:Everyone has always told me that the batteries should be the same age. .They also tell you to not put 2 different oils into your engine and not to mix vodka with beer. But to give more explanation to what I wrote above. Let's say you have one battery that fully charged has 12.5V and you hook up parallel with other one that has 12.4vIf you leave them like that, the lower battery will drain the power from the higher battery. But in RV, you hook them up and almost immediately start using, so after some time they both will discharge to 12.3v for example.At this point the difference doesn't matter.

Second battery | Good Sam Community

narcodog
Explorer II
Feb 28, 2016
My Lance had a compartment for one battery. The first battery was an Optima, I went through three of those over a three year period. They just went bad. I put in a group 31 AGM in year four, I think. Then I added a second battery under the wing of the TC. I used 8ft of marine gauge no 4 cable with an Anderson connection. I ran this set up for about six year without a problem. Last year the older battery went bad so I bought two new ones.
The point being the battery's were not the same age nor manufacture and I got good service from my set up.
jimh406
Explorer III
Feb 28, 2016
Everyone has always told me that the batteries should be the same age. However, I think you have another issue because they are some distance apart. I think I would consider another switch and charge them separately and run them separately as well.

I don't know why you are needing the second battery, but if you haven't switched to LEDs, you probably should.

Finally, I'd measure the compartment and potential batteries. All Group 24, 27s, etc aren't exactly the same size and they also are different amp rated as well.
Kayteg1
Explorer II
Feb 28, 2016
From my experience batteries of different age might mess each other only if left connected in storage for long time.
When you constantly use/recharge the batteries, you always use both regardless minimal differences in voltage.
I run dual batteries in several vehicles and even batteries bought together, having the same manufacture date can show 0.1V difference.
In my boating years I had my travel trailer in storage close to the lake.
With no hookups, I was taking trailer battery home for recharging, but for emergency brakes and short run of water pump I put old motorcycle battery in it.
The recharged big battery would connect with alligator clips to much smaller and much older battery and work whole weekend just fine.
Sam_Spade
Explorer
Feb 28, 2016
Hard to give a good answer without more information.
If the "old" battery is more than 3 years old and/or has been run WAY down more than once, I think it should be replaced too.

No need to separate two batteries into "banks" unless one is a LOT bigger than the other. Two the same in parallel is the most common arrangement in a situation like yours. Unless you got real fancy with the cables, the added one will tend to discharge and recharge slower because of the cable lengths.

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