12 Volt Batteries for Travel Trailer

[pfd701]

I have a 33' Grand Design Reflection travel trailer. It came with one Ultra Power RV24 battery. We sometimes dry camp for up to 2 days at a time. The one battery doesn't last long enough, and I would like to minimize generator use. I would like to replace this one with two new 12 volt batteries wired together. I would appreciate any thoughts and recommendations on what to buy.

Thanks,

Paul 

[richard5933]

Really depends on how much space you have in the battery storage area and how willing you are to reconfigure things a bit. Have you considered going with two 6-volt batteries instead of 12-volt?

Running two 6-volt batteries in series will often give you more storage capacity than two 12-volt batteries in parallel. There are also more options in the 6-volt batteries available. 

[manholt]

Some solar panels on the roof would help also, along with the 6V.

[pfd701]

2 hours ago, richard5933 said:

Really depends on how much space you have in the battery storage area and how willing you are to reconfigure things a bit. Have you considered going with two 6-volt batteries instead of 12-volt?

Running two 6-volt batteries in series will often give you more storage capacity than two 12-volt batteries in parallel. There are also more options in the 6-volt batteries available. 

Richard,

I haven't used the 6 volts due to my lack of experience with them. I have space for 2 batteries. If two 6 volts would give me more storage capacity , I'm absolutely good with that option. What brand(s) and specifications would you look for? 

 Also, are 6 and 12 volt batteries equally at risk of permanent capacity loss if fully discharged?

Thanks,

Paul 

[pfd701]

1 hour ago, manholt said:

Some solar panels on the roof would help also, along with the 6V.

Excellent point. I'm actively looking into this option. 

Thanks,

Paul

[richard5933]

5 minutes ago, pfd701 said:

Richard,

I haven't used the 6 volts due to my lack of experience with them. I have space for 2 batteries. If two 6 volts would give me more storage capacity , I'm absolutely good with that option. What brand(s) and specifications would you look for? 

 Also, are 6 and 12 volt batteries equally at risk of permanent capacity loss if fully discharged?

Thanks,

Paul 

Both are equally at risk if fully discharged. Other than lithium batteries (a whole other conversation) no deep cycle battery does well if discharged below 50%. The more you do this the more the battery is damaged/aged/wears out prematurely.

Six volt batteries give you more capacity per cubic inch, and often in a package that will last longer due to being able to use thicker plates inside. With two 12v batteries in parallel you will add the capacity of the two together, and with two 6v batteries in series you add the voltage together but keep the capacity the same. But, since many 6v batteries of the same physical size as a 12v will have more than twice the amp hour capacity of a 12v battery, you do better with the two 6v batteries.

I prefer Trojan batteries, but there are other top-line batteries which will perform about the same. 

[pfd701]

6 minutes ago, richard5933 said:

Both are equally at risk if fully discharged. Other than lithium batteries (a whole other conversation) no deep cycle battery does well if discharged below 50%. The more you do this the more the battery is damaged/aged/wears out prematurely.

Six volt batteries give you more capacity per cubic inch, and often in a package that will last longer due to being able to use thicker plates inside. With two 12v batteries in parallel you will add the capacity of the two together, and with two 6v batteries in series you add the voltage together but keep the capacity the same. But, since many 6v batteries of the same physical size as a 12v will have more than twice the amp hour capacity of a 12v battery, you do better with the two 6v batteries.

I prefer Trojan batteries, but there are other top-line batteries which will perform about the same. 

I really appreciate your input. Thank you.

Paul

[kaypsmith]

Physical size matters. How much space do you have available?  Two group 1 six volt batteries will take up more room than 2 12V group 24 batteries.  A group 31 12V is taller and much larger than a group 24, but the footprint is a little less than 2 group 24's, and the amp hour (longevity) is far greater than a group 24. Yes 2 six volt of proper size is a good choice but not always will fit into an allotted space. Just make that you check out the footprint of whatever battery you go with.

[rayin]

Six volt batteries, when connected in series to create one 12V battery do not double the amperage, only the voltage. Two 12V batteries when connected in parallel double the amperage, voltage remains at 12VDC

While 6V batteries used to be the best option, that is not necessarily true today.

This explains everything in detail: The 12V side of life

This video might be informative too  https://www.youtube.com/watch?v=iy3hga_P5YY

Edited July 13, 2021 by rayin

[richard5933]

When I installed the battery bank in my coach a few years ago I did lots of research, and given the available batteries the most capacity per cubic inch was with pairs of 6v batteries run in series. Even more true if you have space to go taller with your batteries. Like Kay-smith said, 6v can be larger than 12v, but that's partly why I went with them.

Are you guys seeing some newer 12v batteries which are being sold now with more capacity than just a few years ago? (Not talking lithium here...)

[kaypsmith]

I use 3 12.000 watt gell cell batteries in parallel, that is 36,000 watts total, or 3000 amp hours total. Never allowing to discharge over 50% = 1500 aph usable before recharging, this is about  equal to 16 6 volt golf cart batteries. Each battery weighs 110 # each, and are each just about the size of a group 31 12 volt battery. I use cell phone tower backup pulls. They are replaced every year in my area, new cost about $900.00 each, I paid $100.00 each. Life expectancy is an average of 12 years. Go figure, I hope that I can still find replacements when they fail at comparable pricing.

[richard5933]

7 hours ago, kaypsmith said:

I use 3 12.000 watt gell cell batteries in parallel, that is 36,000 watts total, or 3000 amp hours total. Never allowing to discharge over 50% = 1500 aph usable before recharging, this is about  equal to 16 6 volt golf cart batteries. Each battery weighs 110 # each, and are each just about the size of a group 31 12 volt battery. I use cell phone tower backup pulls. They are replaced every year in my area, new cost about $900.00 each, I paid $100.00 each. Life expectancy is an average of 12 years. Go figure, I hope that I can still find replacements when they fail at comparable pricing.

Remember that in this case we're talking about a travel trailer - weight matters. 

That said, can you share some information with me about the batteries you're using? Perhaps in a PM so we don't get this thread too far off topic.

[desertdeals69]

I would go with 2 lithium 100 amp batteries, half the weight of lead acid, and 400+ watts solar on the roof.  Lithium batteries can be discharged to 90%.

[rayin]

This is one of the 12V deep cycle batteries I mentioned: https://www.trojanbattery.com/pdf/datasheets/SPRE_12_225_DS.pdf

[richard5933]

14 minutes ago, rayin said:

This is one of the 12V deep cycle batteries I mentioned: https://www.trojanbattery.com/pdf/datasheets/SPRE_12_225_DS.pdf

If you look at the Trojan information, you'll see that the 6v version of this battery has 255 Ah at 100 hrs, compared to the 225 Ah of the 12v one you linked to. This is why I went with two 6v batteries in series rather than two 12v in parallel. The 6v version is smaller and nearly half the weight as well.

How does the 12v have an advantage?

https://www.trojanbattery.com/products/deep-cycle-flooded/solar-premium-line-flooded/

[rayin]

Since you do not multiply AH when connecting 2 6V batteries to make 1 12V battery  the advantage is obvious to me. Plus if 1 battery fails you still have another to get by with.

Edited July 13, 2021 by rayin

[richard5933]

2 hours ago, rayin said:

Since you do not multiply AH when connecting 2 6V batteries to make 1 12V battery  the advantage is obvious to me. Plus if 1 battery fails you still have another to get by with.

I see what you mean about the total Ah per battery , but I guess I was also looking at the biggest bang per cubic inch and not per battery. The 12v is bigger and heavier. In the end I guess the best option depends on the individual needs as well as space and weight capacity available.

12v:  1,521 cu in, 225 Ah, 132 lbs = 0.15 Ah/cu in & 1.7 AH/lb

6v:  862 cu în, 255 Ah, 67 lbs = 0.30 Ah/cu în & 3.8 Ah/lb

You can almost put four of the 6v batteries in the same space as two of these 12v batteries, which would provide far more capacity. This is where my math is based, not on the capacity per battery but rather on the ability to shove as much capacity in the allotted space & weight capacity.

[pfd701]

Thank you all for your input. It's been very helpful. Safe travels.

Paul