Adding a second battery

Discussion in 'Power - Site Power/Batteries/Generators/Solar' started by Snowman, Apr 13, 2018.

  1. Snowman

    Snowman Member

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    Jul 12, 2017
    Boulder, CO
    Hey Folks,
    Since most (all, really) of my camping is dry camping, I'm thinking that I should add a second battery to my setup. When I bought my 99 Coleman Santa Fe last July it had no battery so I purchased a Group 27 battery for it, which works pretty well. If I add a second battery, does it need to be a group 27 also? Can I add a group 31 battery to get more AH? Any issue with that?
    Thanks!
     
  2. generok

    generok Well-Known Member

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    Feb 7, 2013
    Anchorage, AK
    Other than mounting issues due to differing physical shape and size, I see no issues with it electrically. I'm not a "battery guy", so I could be wrong, but in my mind, they're both 12V batteries, and if you attach them in parallel, you just get one deeper battery still at 12V.
     
  3. Dback2k4

    Dback2k4 Active Member

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    Jul 16, 2017
    Iowa
    Electrically, it will work. However, rule of thumb is don't mix batteries of different ages, use patterns, sizes, or especially types. I.e. never create a pair that aren't starting their lives as a pair.

    On my pup, I run a pair of Group 27 batteries that are identical, were bought at the same time, and have always been used together as a pair.

    The group size (effective AHs) doesn't make a difference when running in parallel. However, you may not get the additional amp hours from the 31, as your camper will draw amps from each battery simultaneously and you may over deplete the smaller battery (thus shortening its life) while still leaving usable AHs on the newer battery that you can't take advantage of.

    If you're going to run a pair of dissimilar batteries, I'd wire them independently with a switch. Something like this. It's a manual switchover, you may be able to buy a device that would auto switchover, I'm not sure. You could also wire different functions to each battery, like put the furnace on the new Group 31 and leave all the lights, water pump etc on the older Group 27.
    [​IMG]
     
  4. Snowman

    Snowman Member

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    9
    Jul 12, 2017
    Boulder, CO
    OK, sounds like a second G27 is the way to go. This one was used for about 3 months last summer, then kept on a BatteryMinder all winter so I think that it's still new enough to pair a second to it in parallel.
    I just thought that a G31 would give me additional AH but it sounds like that's not the case. Thanks!
     
  5. Dback2k4

    Dback2k4 Active Member

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    Jul 16, 2017
    Iowa
    You could also wire different functions to each battery, like put the furnace on the new Group 31 and leave all the lights, water pump etc on the older Group 27.
     
    Whiteycracker likes this.
  6. Snowman

    Snowman Member

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    9
    Jul 12, 2017
    Boulder, CO
    I suppose that could work. I ran into battery issues a few times last fall, so I thought more power would be helpful, and a bigger paired setup seemed like the ticket. My 5 year old is mostly blind, so we run more lights than most folks (switched to all LED but they're always on in evening) and the furnace draws a fair bit when running. Living in CO, we camp quite a bit in colder weather. Heading out this weekend and lows are projected to be 17 F both nights.
     
  7. Snowman

    Snowman Member

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    Jul 12, 2017
    Boulder, CO
    Not really sure how to wire a battery to just the furnace, but I might be able to figure that out...
     
  8. xxxapache

    xxxapache Well-Known Member

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    If boondocking and battery useage was high on my priority list, I would just buy a small generator. A 1400/1800 Champion can be had for about 200 bucks. They are fairly light....I have been using one to power lights several times a month at a piece of property I frequent.
     
  9. Dback2k4

    Dback2k4 Active Member

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    Jul 16, 2017
    Iowa
    It'd be a massive mod, probably having to build out a separate power distribution system so that the 12V system can still run/charge on shore power.

    Alternatively since you said you run a lot of lights, and if you never use shore power for them (always 12v) then you could just wire them directly to the battery (with a proper fuse of course) and bypass your power system. Just for the lights, of course.

    If it were me, my order of preference would be (Depending on $$$)
    1. Buy a pair of new Group 31s
    2. Form a pair of your existing and a new Group 27 (as you said, yours is new enough to form a pair)
    3. Use a switch and manually failover when one battery got nearly depleted
     
    Snowman likes this.
  10. Snowman

    Snowman Member

    119
    9
    Jul 12, 2017
    Boulder, CO
    Yeah, I think that a new 27 is the way to go cost wise. I'll probably pick one up after this weekend (I have one from a friend to get me through this weekend).
    I don't like the sound of a generator while camping, so that eliminates that idea for me.

    thanks for the help!
     
  11. Dback2k4

    Dback2k4 Active Member

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    Jul 16, 2017
    Iowa
  12. Snowman

    Snowman Member

    119
    9
    Jul 12, 2017
    Boulder, CO
    Thanks for the tip! My current setup is a 20# tank with the G27 box beside. I was going to replace the tank with the new 27 box so the batteries were back against the trailer and then move the tank in front of that setup on the tongue on a new two tank tray (adding a second tank on the tongue simplifies my transport for my spare tank as well).
     
  13. Snowman

    Snowman Member

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    Jul 12, 2017
    Boulder, CO
    I realized that if I move the tanks up front, then my top wind tongue jack won't clear [:(!]
    So, I found a side wind tongue jack for about $50 that I may invest on Amazon. Has a 1000lb capacity, which should be more than enough for my trailer.
     
  14. Snowman

    Snowman Member

    119
    9
    Jul 12, 2017
    Boulder, CO
    [QUOTE="

    If you're going to run a pair of dissimilar batteries, I'd wire them independently with a switch. Something like this. It's a manual switchover, you may be able to buy a device that would auto switchover, I'm not sure.
    [​IMG][/QUOTE]
    Hey Dback,
    I saw your photos on the other post, but it was unclear how you wire up this switch. I assume this is a "1-2-all-off" marine switch that you're using, but how is it wired? Are your batteries connected parallel, and this switch is used to kill the system? Are they wired independently to the switch and it serves as the bridge?
    I like the idea of the switch so that I can kill the system (gas alarm, etc.) while out for the day without having to open the box and disconnect the positive lead.
     
  15. Whiteycracker

    Whiteycracker Member

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    May 22, 2016
    South Chicagoland
    Thats how my setup is.
     
  16. Dback2k4

    Dback2k4 Active Member

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    Jul 16, 2017
    Iowa
    Yes, it's a 1-2-both-off switch. My batteries are wired in parallel. I wired it up instead of switching from source battery A to source battery B to the batteries come in the common (normally output) and the power destinations are on the normally inputs.

    The "input" positive connection for "1" goes to the trailer - lights, water pump, etc. The "2" connection goes to the electric brakes and to an inverter that powers the fridge while I'm travelling. The idea is that when on the road I can set it to "2" for brakes; and while at the campground set it to "1" to power the trailer and keep the inverter from killing the batteries if I accidentally leave it on. If I'm gone all day while camping and need no power in the pup (extending the batteries by killing the CO/LP detector), or while at the storage yard, I can set it to off. And if for some reason I need both (like at home doing maintenance) I can set it to that. The gotchya is the power system for the trailer that includes the charger is on the "1" connection, so if I'm plugged into shore power in order for the charger to charge the batteries I have to have the selector set to "1" or "both"

    I really didn't need such a complicated system, all I really wanted was a battery kill switch for the storage yard, but I had this laying around so wired it as such.
     
    Last edited: Jun 17, 2018
  17. joet

    joet Well-Known Member

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    Elkins WV area
    Just curious as to why you need an invertor to power your fridge when traveling
     
  18. Dback2k4

    Dback2k4 Active Member

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    Jul 16, 2017
    Iowa
    My 3way died and I replaced it with a simple dorm fridge. Most of the time I boondock do I don't even use the fridge, but I occasionally take the camper on multi-week road trips where I camp with hookups, so I wanted to be able to keep the fridge running on those days I drive for 10+ hours.
     

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