New setup off grid camper

MattowensMattowens Registered Users Posts: 7 ✭✭
Morning all just joined and new to this solar stuff. I'm trying to setup an off grid camper in central fl. It's 28' must of the big appliances are gas. No fridge atm. But there is a 13.5btu a.c. Unit. Also I have a shallow well on site. Pump is 1/2h at 110v.

I'm trying to put together a solar system that might run most things most of the time and I can grow it as needed. Use the generator when I must.

I currently have 4 cs5p-240p panels from Canadian solar they seem to be 33v ea. And I have 4 12v 150ah batteries.

I'm trying to figure the most cost effective way to put this together. I was considering setting the batteries up as a 24v 300ah bank and then get a 24v 3000w inverter but I'm wondering if I could set the batteries as 12v 600ah and just run them into the original house battery feeds and use the internal inverter of the camper? Any advice, suggestions greatly appreciated.

Thanks in advance

Comments

  • mike95490mike95490 Solar Expert Posts: 7,364 ✭✭✭✭
    There is a safety concern with running high amps into inverters at 12V  Additionally, the voltage drop issue can quickly become problematic with 12V systems..    2Kw through an inverter at 12V is going to be close to 200A  (load watts + inverter internal losses)
    Same loads on a 24V system = 100A  & via a 48V system only 50A.

    At 200 amps, battery connections can get hot and start to melt the lead terminals, all the crimped connections must be 100% high quality, or they will heat up too, and then you have to deal with heavy, expensive 200A wire

    So only you can evaluate the safety/expense/compatibility tradeoffs, but I'd suggest at least the 24V system.  Do you know how many watts the AC unit consumes? The inverter will have to supply the starting surge for it, which is often 4-10x the running watts.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • MattowensMattowens Registered Users Posts: 7 ✭✭
    Thank you for all of that. That's a lot of information I was not aware of particularly about the heat issue. I don't know the exact specs on the RV air conditioner but on this sitehttps://www.steadypower.com/pages.php?pageid=133 it says it'll run 15 to 2000 Watts and start-up 28 to 3000 Watts. So my initial thought was to get a 3000w inverter so that I could have hampel running when I used it. I would happily use a 24 volt system but I think that would require me to plug the camper in to the inverter just as if I was plugging it into a standard Shore power correct. And my only concern with doing that is the secondary losses from it converting back to 12 volt for the 12 volt systems. But I know it'll do that either way unless I isolate them out.

    If I go 24 volt can I use two charge controllers to each 24v battery keep my amperage down and then combine the batteries at the inverter? And can I use a pwm charge controller or in a condition like this do I need to go with an mppt which are much more expensive unfortunately running out of cash.

    Thanks again for all the information that loan was eye-opening I know I'm just starting out figuring all this out.
  • mcgivormcgivor Registered Users Posts: 1,356 ✭✭✭✭
    @Mattowens said,  If I go 24 volt can I use two charge controllers to each 24v battery keep my amperage down and then combine the batteries at the inverter? And can I use a pwm charge controller or in a condition like this do I need to go with an mppt which are much more expensive unfortunately running out of cash.

    Unfortunately PWM controllers will not work with the panels you have, assuming 60 cell 240W, the voltage would be too high for 12V, which I would not recommend, as well as being too low for 24V nominal, so either way a MPPT controller is required. 

    As far as running an air conditioning unit goes, the array and battery bank would have to be substantially larger than what you have outlined, trying to achieve this is an expensive challenge, especially if any cooling is required outside of peak sun, which is very limited.

    For informational purposes, there is no difference in capacity of a given battery wether configured 12 or 24 volts, example 12V × 600 Ah results in 7200 watt hours, similarly 24V × 300 Ah results in exactly the same 7200 watt hours, the benifit of higher voltage is smaller conductors fuses/breakers etcetera can bu used. Additionally the battery capacity shold be considered at 50% maximum of the calculation outlined above, this is the usable capacity, so as not to over discharge, which reduces life expectancy.

    It would be prudent to reconsider the air conditioning and build a system to support light or intermittent loads, there is little to no chance of achieving it on a limited budget. Please understand these comments are not intended to be negative, but rather pointing out some potential pitfalls most have experienced during the learning curve.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • MattowensMattowens Registered Users Posts: 7 ✭✭
    @mcgivor appreciate all the information, and none of it is taken as negative but very helpful. The only thing i want to point out is the panels are 96cell not sure how that will effect those numbers in regards to the pwm / mppt  Vmp 47.6v, Imp 5.04a, Voc 58.9v, Isc 5.38a not sure if that changes my options. I still expect at this time not to run the AC hopefully one day. I can run the Generator if I need the AC. 

    What I was thinking I might do. Mind there are some obvious things not included on this like bus bars, breakers, etc. Just showing layout options. 

  • mcgivormcgivor Registered Users Posts: 1,356 ✭✭✭✭
    The 24V opinion would be the best choice, given the panel's 47.6 Vmp, MPPT would be the only option, a single 60A controller would be a good fit as the voltage is close to double battery nominal which is perfect. PWM needs the Vmp to be close to the nominal battery voltage, usually around 36V for a 24V system, although a PWM  controller may be able to support 48V, there will be losses which manifest as heat, MPPT down converts the higher voltage convertin it to current, hence more efficiency.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • MattowensMattowens Registered Users Posts: 7 ✭✭
    Ok fair enough. While I have limited funds would prefer it right then wasted. Thanks.
  • mcgivormcgivor Registered Users Posts: 1,356 ✭✭✭✭
    You might want to consider a smaller inverter, some larger ones use up to a kW of energy just being on, without load, some have a sleep function which conserves energy, but it's always best to size according to loads and battery capacity, ask questions if unsure, before buying something that's not what's really needed or compatible with loads, such as modified sine wave, which can destroy some devices.

      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • BB.BB. Super Moderators Posts: 26,976 admin
    It is difficult to piece a system together with existing parts and not really have a good idea of what it is you want to power (average watts, watt*hours per day, peak watts, AC vs DC stuff, etc.).

    For example, 4x 150 AH @ 12 volt batteries (assuming they are standard flooded cell deep cycle lead acid), the typical maximum AC inverter would be around 1,500 Watts maximum for that size battery bank.

    And an arbitrary bank configured as 12 volts ~1,200 to 2,000 watts peak, 24v: ~2,400 to 4,000 watts max; 48 volts >~2,400 to 4,800 watts or more.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • westbranchwestbranch Solar Expert Posts: 4,909 ✭✭✭✭
    MattOwens said  Vmp 47.6v, Imp 5.04a, Voc 58.9v, Isc 5.38a 
    Did I miss  something? if the CC is a MidNite KID 30 Amp model it should be able to handle 4 panels in parallel and limit the output at 30 amps. 
    Just ran a Kid Sizing tool  http://www.midnitesolar.com/sizingTool_kid/index.php   and it indicates that 1.2 Kids would be needed and this note.
    KIDs Required 1.2
    NOTE: MidNite Solar recommends a second controller be added after 1.2
    WARNING: MidNite Solar makes no representation, warranty or assumption of liability regarding the use of the String Calculator. This tool uses data provided by other parties (such as PV module specs) and makes calculations based on assumptions which may or may not prove to be valid..
    so if you fill in the data that you did not supply you may find you are good to go with 1 Kid.otherwise yo should consider a 40 amp MPPT CC of larger if you expect to add to your system...

    Strangely I did not get any hits for the CS5P series, just the 6 series...  If you do plan to expand and the seller still has some stock , best to buy it now as this may be a discontinued line.

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • MattowensMattowens Registered Users Posts: 7 ✭✭
    Thanks for all the information is helping me zero in on my setup needs. Here is what I got
    doc.pdf 15.6K
  • MattowensMattowens Registered Users Posts: 7 ✭✭
    I'm not sure what my needs are I should do some wattage testing. I know the only major electrical devices are ac and microwave. Everything else is propane. The minor devices are a single tv and DVD player. Lighting which is all updated bulbs and some are led more will be as time goes on. Laptop and phones to charge. Overall not a whole lot of power it's a weekender type situation not full time. I figured at a 3kw inverter I could run anything. A ran a 2kw generator on it before with no issues. I figured ac on solar was a expensive pipe dream, but was hoping.

    Thanks again for everything I really am learning a lot.
  • MattowensMattowens Registered Users Posts: 7 ✭✭
    Info from panel manufacturers.
  • westbranchwestbranch Solar Expert Posts: 4,909 ✭✭✭✭
    Microwaive is generally hi draw for short duration,  A/C is hi draw for longer duration add both can add up very quickly.... cell chargers are medium duration and low draw, laptop can be long duration at medium draw depending on age...  but they all ADD UP! total Ahrs or Watthrs are needed.

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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