Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: 24 volt solar wire diagram

  1. #1

    Default 24 volt solar wire diagram

    Here is a basic drawing of a small PV system for emergency backup power. I wanted the system to be 24 volts and will possibly expand its capacity over the next few years. Can somebody please take a look at the wiring diagram and see if there's something I've gotten wrong, forgotten or missed. Any input would greatly be appreciated.

    Click image for larger version. 

Name:	Solar Array design.jpg 
Views:	448 
Size:	50.4 KB 
ID:	4511

  2. #2
    Join Date
    Apr 2011
    Location
    Central Maine
    Posts
    117

    Default Re: 24 volt solar wire diagram

    Two things come to mind. You would want circuit breakers on the feeds from the batteries to the charge controller and the inverter. I do not see any kind of grounding shown.
    Ned
    20 evergreen 210 XW 6048 XW 80 600 16 trojan T105 victron bm custom ground mount all the power we need to live a normal off grid life

  3. #3

    Default Re: 24 volt solar wire diagram

    Welcome to the forum.

    Okay, you don't actually need a fuse on the panels. You should have one on the charge controller output and especially on the inverter.

    Next, a 100 Watt panel isn't going to put out 10 Amps. More like 5. In series this will still be 5, but at 24 Volts instead of 12. This is important because that 5 Amps is not going to do much for charging 212 Amp hours of 24 Volt battery. It will be a peak charge rate below the 5% minimum. It will be about 2%, which is only enough to maintain the batteries.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  4. #4

    Default Re: 24 volt solar wire diagram

    Quote Originally Posted by offgrid me View Post
    Two things come to mind. You would want circuit breakers on the feeds from the batteries to the charge controller and the inverter. I do not see any kind of grounding shown.
    Ned
    Ok, will add some fuses to the leads for the Charge Controller and the Inverter. The Solar Array is grounded and the inverter is grounded as well, although the diagram doesn't show this.

    Quote Originally Posted by Cariboocoot View Post

    a 100 Watt panel isn't going to put out 10 Amps. More like 5. In series this will still be 5, but at 24 Volts instead of 12. This is important because that 5 Amps is not going to do much for charging 212 Amp hours of 24 Volt battery. It will be a peak charge rate below the 5% minimum. It will be about 2%, which is only enough to maintain the batteries.
    I do realize that that the panel isn't going to put out 10 amps, but they are rated as "max" 10 amp panels, so on paper the circuit had to handle 10 amps. I do understand what you are saying that the 2- 100W panels are not going to be enough to charge 212AH 24v battery bank, what I need to understand is how to the determine peak charge rate you're referring to.

  5. #5

    Default Re: 24 volt solar wire diagram

    The current from the panels will be the Imp: Amps at maximum power. This is the most they can put out to a circuit. The rate is expressing that current as a percentage of the battery bank capacity:

    Imp * 100 / Amp hours = peak charge rate percent.

    So 5 Imp * 100 / 212 Amp hours = 2.3%

    Most battery manufacturers recommend a minimum 5% rate, and that is exclusive of any loads.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  6. #6

    Default Re: 24 volt solar wire diagram

    Excellent, thank you very much for the input. I'll put that info to good use and revamp my idea.

  7. #7

    Default Re: 24 volt solar wire diagram

    Click image for larger version. 

Name:	Solar Array 12v design.jpg 
Views:	183 
Size:	56.6 KB 
ID:	4515

    Ok, I revamped the idea to a 12V system and decreased the number of batteries while keeping the capacity at 212AH. The DC circuit breaker is basically a circuit disconnect, it's rated at 10amp, but trips at 13amps. The panels are rated at a max output of 6.2 amps (so the circuit breaker should be alright). I also added the grounding for the panels and inverter and the fuses for the the charge controller and inverter. The fuse sizes i chose should be able to handle everything at peak and still have overload protection. Any input is welcome again. According to my calculations, at 10amp (2 - 5amp panels in parallel), the peak charge rate is slightly less than 5% (4.7%), not ideal,but i do plan to expand in the near future.

  8. #8
    Join Date
    Mar 2006
    Location
    SF Bay Area (California)
    Posts
    20,821

    Default Re: 24 volt solar wire diagram

    Why a 2.5kW inverter?

    A nominal 200 watt solar array will supply a typical 9 month minimum energy of:
    • 200 watts * 0.52 system efficiency * 4 hours minimum sun per day = 416 Watt*Hours per day


    A 2.5 kW inverter may draw 10-20 watts just turned on... Running the inverter 24 hours per day:
    • 24 hours * 20 watts = 480 Watt*Hours per day


    So--Just running the inverter 24x7 can use use most of the power your solar array generated in a typical spring/fall day.

    The only way I see running a large inverter like this on a small system/battery bank is if you 1) manually or automatically control the DC power to the inverter, 2) have a load that has high starting surge and/or high power required for short periods of time--such as water pumping, and 3) you use AGM batteries that can supply high surge currents and are more efficient/lower self discharge than flooded cell batteries.

    We have two ways we can proceed here--First would be to backup and define your loads, then design a system to run them. Or second, we can just run the numbers (like above) on what the system would be capable of supporting.

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  9. #9

    Default Re: 24 volt solar wire diagram

    The size of the inverter depends on what you want to run. It is doubtful that you'll need 2.5 kW output (greater than one standard outlet which is 15 Amps @ 120 Volts = 1800 Watts) and as Bill said the bigger the inverter the greater its self-consumption. So check the numbers on that for any inverter you look at, as it has to be included in the over-all load.

    212 Amps hours @ 12 Volts gives you about 1 kW hour of power to work with at 50% depth of discharge.
    200 Watts of panels will 'harvest' about half that on a good 5 hour day.

    I don't know where you're getting 100 Watt panels from (hopefully not homemade), but most of the 12 Volt panels available these days are around 140 Watts and that extra 80 Watts would be welcome.

    Further, using two 12 Volt batteries in parallel will not work as well as two 6 Volt batteries in series due to the possibility of current sharing differences. A couple of golf cart batteries may cost less too, and give you about 220 Amp hours @ 12 Volts.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  10. #10

    Default Re: 24 volt solar wire diagram

    Ok folks, I appreciate all this input. I'll have to look into 6V golf cart batteries. Basically this system is designed for use when the grid fails. The solar panels charge the battery bank till full and maintain a float charge.

    When the time comes and power is needed, I will use this to run appliances like the freezer (around 700-900W) and an additional 500W or so to run fish tank heaters and pumps. I only will be using the power in 1-2 hours bursts, just to maintain. I went with the 2500W inverter because I do want to eventually expand the panels and batteries to be able to power stuff for longer.

    The 100W panels are from grape solar http://www.grapesolar.com/index.php/...s/gs-s-100-ts/

Similar Threads

  1. How do I determine what gauge wire I need for a 12 volt system.
    By nobody928 in forum Solar Beginners Corner
    Replies: 4
    Last Post: December 4th, 2013, 8:32 PST
  2. Corrections made on 24 volt Battery Bank please advise - Diagram Included
    By cdrudge in forum Off Grid Solar & Battery Systems
    Replies: 5
    Last Post: June 11th, 2013, 17:14 PDT
  3. Advice needed on 24 volt Battery Bank Diagram Included
    By cdrudge in forum Off Grid Solar & Battery Systems
    Replies: 3
    Last Post: June 9th, 2013, 20:15 PDT
  4. 36 Volt Wire Chart
    By Joe J in forum Off Grid Solar & Battery Systems
    Replies: 4
    Last Post: October 20th, 2012, 8:32 PDT
  5. Wire Connection of devices diagram (How to)!
    By Sharp230 in forum Solar Beginners Corner
    Replies: 2
    Last Post: October 1st, 2012, 19:34 PDT

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •