215w solar panel

I am new to solar energy but i want to install 215w panel and need 700watts everyday. I have some questions to ask.
1: what system would you suggest, 12v or 24v and how many 12v or 24v battries will i need? and which power inverter and charge controller should i buy?
2: how many 12v and 24v battries can be charged in 8 hours by 215w panel?
please help. thanx in advance.


  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    Re: 215w solar panel


    For anyone on this forum to better advise, you will have to supply and/or correct some of the info you supplied:

    1. what is your environment like so a derrating factor can be appro. for the peformance of your solar panel (in the winter where the batteries many be affected more and summer where the panels will be affected more)

    2. your energy usage in terms of watt hours and not just watts. so you need to approx the time of the usage times the operating watts of the items you want to power and add them up for your total.

    3. Generally you can get 12v inverters cheaper than 24v inverters. also i have read that the rule of thumb is that if your max. require wattage (surge) is greater than 2000w then you should be looking at least 24v system to minimise the cose of cable runs and fuses/breakers. so since you have a small system i would say you will be probably looking at a 12v system.

    4. Specs of the panels (V & I oc , V & I mp)

    the amount of storage (or how many batteries) will depend on point #2 in this reply and to a lesser extent point #1 (depending heavily on the environment the battery will be stored in)

    since you have only one panel you will only need a small CC, unless you plan to expand soon and prefer to get a bigger one for future expansion. If planning for future expansion you should ideally buy more panels identical to the one you have now. if your panel Vmp is greater than 18v using a PWM CC (cheaper one) you will lose power changing a 12v battery. Max power harvesting will be achieved by using a mppt CC (more expensive)

    I hope this helps

  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
    Re: 215w solar panel

    As Damani said...

    Typically, you need to measure/estimate your load first... Normally in Watts*Hours per day...

    700 watts * 1 hour = 700 Watt*Hours or 0.7 kWh per day
    700 watts * 24 hours = 16,800 Watt*Hours or 16.8 kWatt*Hours per day

    Assuming you are in/around Dubayy of the United Arab Emirates... You probably have lots of sun in an average day. Lets assume you have a good 6+ hours of "noon time sun" per day... As a very rough average, a 215 watt solar panel with an MPPT solar charge controller on flooded cell Lead Acid batteries and using an AC Inverter for 230 VAC 60Hz (or whatever is used in your region):

    215 watt panel * 6 hours of sun * 0.52 system efficiency = 670 Watt*Hours per day (good weather, summer time).

    670 Watt*Hours (or 0.67 kWhrs) is not a lot of solar energy... To run a small radio and some florescent/LED lights--perhaps charge a laptop computer after 1-2 hours of use is about it.

    But--it depends on how much power you need... If you only need a little bit--then you will be pretty happy.

    Battery wise, normally, we recommend a battery 20 Hour Rating (in Amp*Hours) around 1/0.13 to 1/0.05 of your peak charging current...

    For a 12 volt system, 215 watt panel with MPPT controller, roughly your battery should be around:

    215 watt / 15 volt (battery charging voltage) * 1/0.13 = 110 Amp*Hour Rating
    215 watt / 15 volt (battery charging voltage) * 1/0.05 = 287 Amp*Hour Rating

    A typical full size 12 volt car battery is probably rated around 80-100 Amp*Hours--but always use a "storage battery" for solar applications--not a car battery. A car battery will not last very long--they are designed to start cars.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset