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I am new to this forum and pretty new to offgrid solar systems as a whole. I am in some form of trouble and need some expert, but quick advise. So here we go.

I have a 600w load connected to a 4 * 100 ah battery bank which has been configured for 24volts. The battery bank is being charged by 800w panels(100w panels(12 volts) * 8) which is also set to 24volts. The charge controller which charges the battery is made by Rk Solar and has a digital display in the front to display how much percent is my battery charged at any point of time.

Before connecting the load to the system i just wanted to check whether the controller was perfectly or not. So i wired up everything except the inverter/DC output from the controller.

Now is the bizarre part.During daylight, ie from 9 AM – 5 PM the controller shows the battery charge climbing from say 40% to 100% within 6 hours or so. Once the sun goes down, according to the controller that battery charge climbs down from 100% to 30% or low in some cases with no loads attached.
The discharge occurs within an hour or two. The controller is pretty new and is rated at 24v/40A.

What might be causing this?

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My current solar system for home:
1. 12V 100W polycrystalline Solar Panel.
2. 12V 75Ah Lead Acid solar tubular Battery.
3. PWM 12V 10A Solar Charge Controller.
4. 12V Input and 200VA Output Inverter.

Current Problem:
Battery not getting charged fully daily because solar panel is getting around 3-4hours sunlight and that too includes sunlight at non-90 degree conditions.

So, I want to add an additional solar panel[preferably 200W or more] which will get 90 degree sunlight from 1pm to 5pm. Also, we get around 50 minutes of on grid supply. During this time inverter charges the battery too.

My questions as per my whole day research:

  1. If I add a 24V 200+W solar panel, I have to connect the panels in series because
    parallel means same voltage but ampere gets added.
    series means same ampere but voltage gets added.
    In this cases what changes are needed to charge the 12V battery?
    I guess someone will suggest MPPT controller. What is the best controller available in India? budget max6000INR

  2. To avoid huge costs and hastle for the above requirement if I go with 12V 150W panel, then I will just need to connect my 12V 10A with a new 12V 20A controller in parallel to draw 8.6+12.5A=22A approx. current from solar panels.Am I correct here?

  3. During a hot and shiny summer how much watts does a 100W panel produce in 90 degree sun conditions? What is the worst output that I will get in rainy season?

  4. While charging battery from the inverter during grid supply, I see the inverter shows around 6A-9A current supply to the battery. Is it the current only that counts how fast the battery goings to be charged. Does change in voltage play any role?

  5. I want to pull as much current as possible from grid and put it to my battery during that 50min time. What device will let me do so? Logically to charge a 12V 75Ah battery from 0-100 we will need something that putts 900W of power into the battery in an hour.
    900/12=70A approx. How much Ampere is safe for longetivity of battery?

P.S: In any circumstances safety and device efficiency is my priority.Please excuse any non-sensical thing if I mentioned above.

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I want to learn about solar charge controller

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Hello sir,
I have 2.5 acres land in village Rajkot district, I planned to install 1 MW
solar power plan and I want to sell industries near my region. so, help me
1) cost of system
2) Which certificates we required?
3) government policy.
4) How much money i have to invest and how much loan?
5) If i give power to government and what is unit rate ?
6) loan subsidy from government and interest of % .
please share other information.

Mukesh Parmar
203, Rameshwar complex ,sadar,
Email Id – mukesh2pmr@yahoo.com
mobile no – +919825158331

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i am planning to install a on grid system with a capacity of 2kw for my home with monthly consumption of 350 watts average. how many panels i need, what are the items needed with capacity spec. what would be approx cost ? what is the warranty period for the panels and other parts? Any AMC is there ?


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I am having a 10Wp solar panel & 12V 7ah battery. Is it possible to make a mobile charger & 100w inverter from this ?. If so, how ?

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How to Install and Maintain Solar Panels?

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Want to convert solar energy to electrical energy to run 3phase 5hp water pump

No batteries to be used and minimum circuits

Thanks & Regards
Rakesh Chavan
Unique Technologies
Pune, India

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