12 volt versus two 6 volt - Fiberglass RV


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Old 08-11-2018, 11:16 AM   #1
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Name: Michael
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12 volt versus two 6 volt

Hi

Have a 2017 25’RQ Bigfoot trailer. Will be putting 320 watts (2 panels) on the roof. All the lights are led and we charge phones, laptops etc. We are not heavy energy users, but do have the refrigerator fan as well as heater fan (when needed) and water pump.

Do I put in a deep cycle agm 12 volt or two six volts wired in a series.

Thanks for your input.
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Old 08-11-2018, 11:54 AM   #2
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Originally Posted by Nvboatman View Post
Hi

Have a 2017 25’RQ Bigfoot trailer. Will be putting 320 watts (2 panels) on the roof. All the lights are led and we charge phones, laptops etc. We are not heavy energy users, but do have the refrigerator fan as well as heater fan (when needed) and water pump.

Do I put in a deep cycle agm 12 volt or two six volts wired in a series.

Thanks for your input.

From what your are describing as your useage IMHO 320 watts is way more than you'll ever need. (I have 65 Watts, charge phones, laptop, etc and run LED lights and heater fan. Need to recharge about every 4 days when using the furnace, the battery is a group 24 Walmart 74amphour deep cycle battery (12Volt))

I suggest before you spend a lot of money on over kill you calculate usage. There are lots of articles about how to do that.
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Old 08-11-2018, 12:42 PM   #3
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I've got dual golf cart batteries in my Escape 21, for a total of 12V 210AH, and a 160W solar system on the roof, my batteries are usually still at 90% when the sun comes up.
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Old 08-11-2018, 01:16 PM   #4
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done....

this topic has been done to death around here....


but to your particular situation....


the balancing act is: usage / production / storage.....change one number and you can change one or both of the other two....ad infinitum....the goal is the less dollars and less weight that meets your "usage" requirements



in your case you have a TON of "production"...(as long as you're parked in the sun)...so you could go light on "storage"....I guess....have fun figuring it all out.
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Old 08-11-2018, 01:25 PM   #5
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and as John says....

160 on the roof is "substantial"....if I were you, I'd buy just one of those two 160s you're planning on....and get a 50 or so portable with an extension cord to cover all your bases (parked in the shade)....I only pick 50 as a number because when you get close to 100 they get pretty big/hard to handle/store easily
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Old 08-11-2018, 01:25 PM   #6
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The two 6V golf cart batteries will give you much more storage capacity than any single 12V of reasonable size. If you have room for them it's an easy decision. Do the calculations of your usage if you are interested but nobody complains about having too much, production or storage.
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Old 08-11-2018, 03:00 PM   #7
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The two 6V golf cart batteries will give you much more storage capacity than any single 12V of reasonable size. If you have room for them it's an easy decision. Do the calculations of your usage if you are interested but nobody complains about having too much, production or storage.


Agreed.
No one complains because they have too much truck, too much solar power or too much battery capacity.
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Old 08-12-2018, 10:58 AM   #8
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160 on the roof is "substantial"....if I were you, I'd buy just one of those two 160s you're planning on....and get a 50 or so portable with an extension cord to cover all your bases (parked in the shade)....I only pick 50 as a number because when you get close to 100 they get pretty big/hard to handle/store easily
The semi-flexible solar panels are not very heavy. I just lay mine on the bed when on the road.
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Old 08-12-2018, 11:15 AM   #9
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Do I put in a deep cycle agm 12 volt or two six volts wired in a series.
I considered dual 6 volt batteries but I installed dual 12 volt batteries instead. My reasoning is with 2 six volt batteries, if one battery goes bad you don't have any power. With dual 12 volt batteries if one of the batteries goes bad you can disconnect it and still have usable power.
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Old 08-12-2018, 01:01 PM   #10
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Agreed.
No one complains because they have too much truck, too much solar power or too much battery capacity.
Usage over time will change as you are able to add more devices or want your cigarette lighter inverter on more of the time. You may add a stereo, a DVD player or other things to make life more fun or comfortable. Then the roof collectors may not be adjustable and will not produce their rated output, or you want to park in the shade sometimes or the collectors get partially shaded or dirty. Then you'll eventually camp in poor weather (that's when I like to go) and the output will be low. Don't count on the rated output of the collectors unless you use a portable setup on the ground that you clean and adjust properly all day.

It seems usage will always rise to meet capacity and capacity may not be what you calculate it "should" be.

Batteries will be much happier if they don't get discharged as deeply each time and if they spend more time in a fully charged state. They will slowly sulfate (especially if they are not repeatedly fully charged) which reduces their capacity. Ideally, they would get driven up to about 14.1 volts every day and rest at about 12.65. Not likely to happen. So, go with more instead of going with just enough. Try to figure in real world deficiencies that don't show up on paper. The whole system will serve you better over time if you allow for the things that make it imperfect.
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Old 08-12-2018, 01:45 PM   #11
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Portable Solar Panel

The 120W Go Power suitcase-style portable panel that I use with a 30 ft. cord only weighs about 25 lbs. Zippered suitcase with a handle and fits on the floor of the trailer when travelling. Keeps my 12V electric-only fridge running with two 12V batteries, for at least 3 days if there is no sun. All lights are LED. Haven't used the propane furnace with the fan with it yet.


The 30 ft. cord makes it easy to park my trailer in the shade and have the solar panel in the sun all day with a few adjusts so it's always facing the sun. The panel folds in half and comes with it's own built-in adjustable aluminum stand and charge controller. Not inexpensive, but very usable.
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Old 08-12-2018, 04:10 PM   #12
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I considered dual 6 volt batteries but I installed dual 12 volt batteries instead. My reasoning is with 2 six volt batteries, if one battery goes bad you don't have any power. With dual 12 volt batteries if one of the batteries goes bad you can disconnect it and still have usable power.
Our experience has been if one battery goes bad the other one is bad also most of the time. But with 2 12 volt batteries you have a lot of capacity. We have a Casita with one battery and it will run out of juice at times if running the furnace. On our motor home we have never run out of juice but have had to replace both batteries when one goes bad since the other one is also. So the idea of one bad battery leaves you one good one is not true a lot of the time.
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Old 08-12-2018, 04:36 PM   #13
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My truck has two starting batteries wired in parallel. One went bad and would pull the other one down too.
Once I figured out which one was actually the bad one, I was able to take it out and run on the other one until I could get new ones. I think it's best to replace both, but that's because they are the same age, not because they both fail at exactly the same time. If one shorts internally, it will drain the second one, but once isolated, you can keep going until it's convenient to fix it.

My Oliver has four batteries. Two banks of two each, wired in parallel. I'm just about to install a marine isolation switch so I can remove either of the two banks that have a problem simply by turning the switch.
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Old 08-12-2018, 06:46 PM   #14
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Parallel batteries might present different impeadance to the charging circuit and draw different currents, resulting in different charge levels.
Series batteries will, by definition, have exactly the same charging and discharging currents.
This is a good thing
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