motorhome solar system question

I have 3 solar panels on top of my motorhome, each panel is 300w 12v. the way they are wired at the moment with the connectors they each panel came gives me a total of 100v in full proper sunlight. I have 2 deep cycle 12v batteries as well as 6 other 12 car batteries that I've accumulated. first question is do I really need any batteries other than the 2 deep cycle 12v's I have? and do I need a charge controller that has the ability to charge 2 batteries? or maybe a better question really is can anyone tell me the proper way to keep a battery bank charged using the solar panels I have, and how I should have my system setup before I end up making a uneducated and possibly expensive mistake!  I'm new to this and I want to be properly educated solar and battery power applications. I appreciate any guidance and knowledge I can soak up from others here who have the knowledge I do not.

Comments

  • EstragonEstragon Registered Users Posts: 1,619 ✭✭✭✭
    In order to figure out battery needs, you should have a handle on loads in terms of total watt-hours and maximum instantaneous wattage, and an objective for time before needing shore power or generator. In mobile applications, space can be a limiting factor. That said, if you will just be relying on batteries for 12v lighting and phone charging, a couple of deep cycle 12v batteries may work fine.

    A 12v panel would typically put out 17-18v in full sun and reasonable temperature, and you would see ~50odd volts if 3 were wired in series. Seeing 100v from the string, and the rating of 300w each, suggests they aren't 12v. If so, you will need an MPPT type controller to charge a 12v bank.

    Car starting batteries are designed to deliver high currents for a short time and then be almost immediately recharged. They don't generally work well as house batteries. Using them would also mean putting them in parallel, which can be difficult to keep balanced (especially if the batteries have varying health to begin with).
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • WestoniaWestonia Registered Users Posts: 3
    edited August 23 #3
    on a day like today, full sun and in the low 90's. My 3 panels are putting out 105v.
    Here are the  specs on my solar panels...... I have 3 all exact same specs: I live in my RV no generator and I'm constantly moving so I rarely have the option of shore power. my main goal/issue is having minimal 12v lighting at night and charging phone's/tablets/ and my computer. I'm a musician and at night I need enough battery bank power to run my Mac mini and my 18" flat screen monitar, and 2 6x9 speakers and a sub powered by my surround sound ampreciever. so I'm just trying to figure out the magic combination of daytime charging power, number of batteries, to give me power to finish recording my album at night. I have a 2000 watt continuous 4000 Watt peak power inverter that I'm using to power my AC needs in the evenings.
  • mike_smike_s Registered Users Posts: 39 ✭✭
    Those are "24 V" panels. You need an MPPT controller to get the maximum power out of them for a 12 V system. What controller do you have now?
  • ThomThom Solar Expert Posts: 169 ✭✭✭
    You need to list all the components of your system. What brand and model . 

    Thanks thom
    Off grid since 1984. 430w of panel, 300w suresine , 4 gc batteries 12v system, Rogue mpt3024 charge controller , air breeze windmill, Mikita 2400w generator
  • EstragonEstragon Registered Users Posts: 1,619 ✭✭✭✭
    With your 3x245w panels you can support around 300 amp hours of 12v batteries. You don't want to run them down more than halfway on a regular basis, so you have around 1800 watt hours for loads on battery power.

    A 2000w inverter will use a fair bit of power just being on, so you may want to keep it turned off when not needed, and avoid running it just to charge a phone or other small load. The speakers and sub may take a lot of power depending on volume etc.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • WestoniaWestonia Registered Users Posts: 3
    edited August 23 #7
    currently I do not have a charge controller...here is a list of all the equipment I currently have for the system:
    1) Charge Wizard
    1) Cen-tech Power Inverter
    2) Interstate 12 deep cycle batteries
    3) Boviet solar panels Models: BVM66101-245

    here is a link to pictures of all this equipment and stats for each unit, and a picture of my 
    1973 Dodge Roadliner with a big block 440 that through much trial and experimentation, I have successfully set up a gasoline fuel vapor system I've designed and it's performing flawlessly now, purring like a kitten!  no more burning wet fuel in the gas guzzler....

    https://drive.google.com/folderview?id=0By8WjgxTUsHybWNwZDhzengwWjg
Sign In or Register to comment.