Stupid idea?

RISOverlandRISOverland Posts: 2Registered Users
We have built a small offroad trailer and i run a small solar system for lights, recharging devices, a water pump and a 12v fridge freezer. I have (2) 100ah windy nation batt's, an Epever mppt controller and (2) 100w monocrystalline windy nation panels. The system is 2 years old and has worked great but with the addition of the fridge this year, the limits are being pushed in less than perfect campsites.Recently we were 4 days at a very shaded camp and i hit my low limit on the last day. I was actually surprised we did that well.
Well i want to add another battery but I understand its not great to just add a new battery into a 2 yr old system and would rather not at this time.
However, now we have a few camping events coming up (this weekend being one) and today i bought an Everstart Maxx 105ah marine deep cycle as a backup to charge and throw in the jeep for this weekends camp.
I did not intend to add it to the system per se, but then i wondered if i could wire this battery directly to the + and - bus bars that i use to distribute our power to lights and all. So in other words the solar will feed the bus bars and this new battery will too but not as part of the 2 battery bank. Would this do any harm to my system, drain the other batteries or be dangerous or just be stupid? thinking the latter.
I was just going to have this battery in the jeep and hook it to the fridge should we run low in the shade again. I would like to have it tied into the bus bars for lights and all too if possible.
Any thoughts are greatly appreciated...good and bad 😉


  • littleharbor2littleharbor2 Posts: 1,027Solar Expert ✭✭✭✭
    You could probably add it into the mix at night but I wouldn't recommend leaving it connected during the day being your existing batteries will be at a different soc. Maybe even hold out adding it till you need it. When you get back home get it on a charger asap to avoid sulfating.
     Something you might try is adding a freestanding panel that you could set up optimally aimed at the sun throughout the day. 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • RISOverlandRISOverland Posts: 2Registered Users
    So if i hooked it up at night for help with lights and the positive bus bar had 2 power supplies coming to it (solar side and marine batt,) would it drain on the stronger supply until they balanced out?
  • littleharbor2littleharbor2 Posts: 1,027Solar Expert ✭✭✭✭
    That, I don't know. I'm just thinking your house batteries shouldn't begin their charging cycle with a guest in a different state of charge.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • NANOcontrolNANOcontrol Posts: 78Registered Users ✭✭
    I'm thinking you don't have enough panels to do even your old system right, there likely isn't enough current. An actively used system hardly ever gets out of bulk charge, so what's the difference. Your batteries don't fully recover till you park it and don't use it. I would have each battery on a switch and cycle one battery at a time when it is not used for a while.  I do run a parallel "house battery" which switches on and off the other battery automatically as evening approaches. It doesn't matter because it was a crap battery to begin with.Having batteries sitting around unused will probably do more damage.
  • mike95490mike95490 Posts: 7,901Solar Expert ✭✭✭✭
    Maybe using a smart battery isolator for RV's would be a good way to use any surplus, to recharge the 2nd bank

    Morningstar Solar has a  dual battery charger too


    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

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