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Old 02-16-2018, 10:21 AM   #1
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Adding another 12v battery to camper

Hi all, The dilemma I ran into last week winter camping showed me two things.
1. Without sunny days I cannot run my furnace, as the battery gets sucked of power (below 10v)

2. I need to add another battery so I can continue to camp off grid through the seasons. I charge my battery with 100 watt solar panel and am happy most of the time.

So. My current 12v is mounted behind my propane bottles on the tongue. I have limited space there for a second 12v battery. I'm thinking of installing the second under my bench seat, within a few feet of the current battery (meaning I would buy a sealed lead acid), and run a parallel connection to the outside battery.

Any thoughts on this? I installed my charge controller in that location, so I can read battery power/solar input while IN the camper. I ran the wires to the charge controller from the outside battery, under the bench seat. So I'm thinking I can use the same hole I drilled to run the 2 or 4 AWG battery cables to the new battery. The run will be about 3 feet. I know I'll have a bit of loss but I'm not too concerned with that.

Thanks for your feedback.
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Old 02-16-2018, 12:58 PM   #2
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With slight trimming of a handle or two on the battery boxes, you should be able to fit two group 24 batteries on the tongue. Two group 27s won't work though.

Another option is to change out your existing one for two deep cycle 6 volt batteries. These will give you a lot more boondocking capacity than a standard group 24. I'm not sure if these would fit on the tongue without modification. I know people have made racks to put four batteries above the frame rail, but four batteries is a lot if you aren't full timing.

Sealed batteries sometimes need venting, so I'd be concerned about airflow having it stored and working inside, but I'll leave that for the experts to explain.
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Old 02-16-2018, 06:57 PM   #3
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I have a T1700 there is room for two group 24's that will give you 160 amps. I don't think two 6's will work because of their height just parallel the two together if you don't have to don't put it inside it will save you a lot of grief. The furnace is a power hog there is no getting around that. In the winter your not going to get much over 4 hours of strong sunlight so you maybe pushing it with a 100 watt panel. You TV can be used to charge your batteries if it is a factory wired setup in a pinch.
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Old 02-16-2018, 08:04 PM   #4
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thanks folks, I will take a gander at buying a group 24. I will check to see if my current battery is a 24 or 27. I've had the battery for 3 years now so it may also be time to get a new one (and move that one to my solar powered workshop). I can also look at another 100 watts for the winter and late fall, early spring sunlight.
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Old 02-16-2018, 10:22 PM   #5
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Hi Kit,

I have 2, group 27's on mine. I had to make a pressure treated wood adapter to turn the batteries 90 degrees.

This post has some good info that may help and the post their after with pics of jsms264 2 group 27's on his T264SR. He also made a 90 degree rack. Battery question...part 2, group 24 or 27?

Here are a few pics of the adapter setup. I can get more if this is of interest. I did have to find the right battery box cover to fit. The box was not the problem but the cover was. Some overhang more then others. 2 group 24's will be easier then 2 group 27's if you can get by without the extra capacity.
















You mentioned bringing the battery inside the camper under the front area and you also said a "sealed lead acid battery". Heads up on that. If this is a deep cycle lead acid battery, I have not seen a real sealed one. This technology bubbles the electrolyte during charging and creates hydrogen that has to vent. They need water added from time to time too. The cap systems are vented to let the gas out. While they may look like a sealed battery, the caps do come off. When used inside a compartment, they need a vented compartment.

I have not seen a true sealed lead acid technology deep cycle battery. They may now make one, just I have not seen them. Check with the manufacture of the battery if it can be used inside without special venting in place. And if they do make one, please post the brand and type you found. They are not common.

Hope this helps

John
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Old 02-16-2018, 11:11 PM   #6
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Thanks John, I knew I'd hear from you and appreciate the photos. I can rig up the two batteries like you did, or even weld if needed.

I'll post photos. Going shopping for the battery and boxes.
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Old 02-17-2018, 05:34 AM   #7
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Not to complicate things, but if you add another battery, wont you need more panel to charge? In my reading before I set mine up, I determined that my 2 battery bank needed about 2 panels for my goal of having a quick charging system. I’ve got good performance from my 2 panels and 2 batteries. I symphasize the furnace must draw one battery pretty quick, especially if you go into a night with low battery due to weather.
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Old 02-17-2018, 05:38 AM   #8
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A group 27 battery is a bit over 2" longer than a 24 and two 24's just fit inside the tongue framework. Mine sit on top of a 1/4" piece of lexan if I used some thing a bit thicker they would then be too tall and would interfere with the camper body work both the 24 and 27 are the same height. There are plenty of charts online that will give you sizes by group number. The difference between a 24 and a 27 is only about 10 amps so that might be a consideration in your configuration for 20 amp total it maybe easier to use the small batteries that might fit without a lot of extra work.
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Old 02-17-2018, 09:11 AM   #9
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I will have to look into that. My traveling buddy has two batteries and she uses 100 watt renegy folding panels. How much wattage in panels do you use.
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Old 02-17-2018, 09:31 AM   #10
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Do you think 12v, 75AH is enough? I'm shopping on Amazon for a new group 24. But will probably buy it at Oreilly's in a town near me. BTW. I live and travel in the southwest, where our days are sunny more often than not, and, so far, 100 watts has worked for single battery, if I need more solar, I can use another 50 watt from my off grid shop. Or get another flexi 100 (i am always concerned about weight)
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Old 02-17-2018, 09:46 AM   #11
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2 type 27's fit just right on the factory rack of my T1950
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Old 02-17-2018, 10:13 AM   #12
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Can you compare the Group 24 to Group 27? Weight? voltage? I'm going to buy a new pair. I see the battery I have now is a group 24. This morning it is charging from 11.1. It was 16 degrees outside this morning. Colorado


thanks, Kit
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Old 02-17-2018, 10:43 AM   #13
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Quote:
Originally Posted by Photokit View Post
Do you think 12v, 75AH is enough? I'm shopping on Amazon for a new group 24. But will probably buy it at Oreilly's in a town near me. BTW. I live and travel in the southwest, where our days are sunny more often than not, and, so far, 100 watts has worked for single battery, if I need more solar, I can use another 50 watt from my off grid shop. Or get another flexi 100 (i am always concerned about weight)
If you are looking at 2 new batteries, think hard about getting 2 6 v deep cycle, premium batteries like crown (there are other good ones too, like Trojan, I think). They are a little more expensive, but better built from what I can tell. I found them a little hard to find and a lot of dealers wanted to charge msrp but good prices are out there (I found that we have a crown regional distribution center the next town over and I got a great deal there on the loading dock). Size names are different, but sized similarly to 12 v.

I have 200 watts on the camper and 105 amp hours of batteries (I think).
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Old 02-17-2018, 12:23 PM   #14
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Quote:
Originally Posted by Photokit View Post
Can you compare the Group 24 to Group 27? Weight? voltage? I'm going to buy a new pair. I see the battery I have now is a group 24. This morning it is charging from 11.1. It was 16 degrees outside this morning. Colorado


thanks, Kit
Hi Kit,

I moved this reply to your thread over here. It fits better here then the 2012 thread.

Wow...16 degrees.... That's cold.

On your 11.1 volts this morning, is this the battery voltage with nothing running off battery in the camper? If so that means your battery is completely discharged. Meaning there is nothing much left. If something was running and it was 11.1, then it is down but may not be totally drained just lowered by the power draw. To get a accurate voltage for a state of charge reading, turn all 12 volt things off and then check

This link will help on battery voltage and state of charge when a battery is at rest. Scroll down to Table 1 State of Charge as Related to Specific Gravity and Open Circuit Voltage.
Battery Maintenance | Trojan Battery Company

A battery being that drained or even close to that far down is a problem with it being that cold out on the battery itself. Hoping today it warms up above freezing. A battery that deeply discharged can freeze if it is out in those freezing temps long enough. If today warms up, you have a chance of recovery.

This leads me to the next issue. If your battery is drained way down, let's say 100% to 80% discharged, (meaning you have no state of charge or only 20% available, ) the next issue is charging it back up. If you have a 100 watt solar panel, and I will pick 13.6 volts not knowing a better one, this comes out at 7.4 amps max output. And ideally you only drain down to 50% discharged for longer battery life before recharging.

I am not a solar wizard by any stretch yet, so Mainah and Tod can fill in if I miss-speak, but it is going to take a real long time at a max of 7 amps to recharge your single grp 24 battery from being drained that far down. I know it will not reach 100% recharged by nightfall tonight. That would take a few days with not using anything in the camper. It might get up towards say 60 or 70% charged. And the furnace is going to drain that all over again.

I do not know enough yet about the solar charge controllers and the one that you have, I do not know if you will get a full 7 amps charge for 10 hours straight of sunlight. This brings us to the next topic.

If you have 2, grp 24's or 2, grp 27's you have to recharge them. Doubling the capacity buys you more time or capacity, but only once. Once it is drained down you have to recharge it and it takes time to do that. If you do not increase the solar wattage, the time will take twice as long of whatever it is today.

Point being, going day after day into a highly drained battery situation, if you cannot recharge it far enough to make it through the next night, it will catch up to you as you cannot recover.

I got to go now, be back later.

Hope this helps

John
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