I find that manufacture specify 12.8V 40AH LiFePO4 battery in case for a 40W Solar Street Light whereas 12V 100AH Lead Acid Battery. • You only intend to use the system in summer, so you need a panel that is 43/4 = 11W or more. What will happen is that the fridge will be draining power from the battery whilst the solar panel is putting power back into the battery. Now as I said before, this is a high power example, more typical of a large offgrid caravan or motorhome, but the approach is the same. From here there is a bit of mathematical mumbo jumbo in selecting the correct blanket size based on the loads you're taking and the battery bank size. When charging your batteries from a good battery charger over a number of days, you can get to 100% charge. Is there a different yardstick to determine battery size incase of Li-Ion or LiFePO4 battery vis-a-vis Lead acid battery. So that 120Ah battery you have, esentially cut the useable amount by half. 8.76 kW Grid Tied Solar System with SolarEdge and 24 Astronergy Solar 365 watt Panels UNBOUND SolarEdge Gridtie System for 24 Astronergy 72 Cell Modules $ 12,406.00 So, how many 100 watts panels do you need? You’ll need to make sure you connect your fridge and solar panel directly to the battery, don’t connect the solar panel directly to the fridge. There are other solar panels with various power ratings you can install to charge your batteries such as 100 watts, 150 watts, 235 watts, 250 watts and many more. So you need 1200 / 250 = 4.8 hours of bright sunlight. It will depend on two factors, Add 5W for each additional 60Ah of conventional battery capacity or 120Ah of sealed gel/AGM battery capacity. And you need a charge controller suitable for a solar input of at least 11/16.5 = 0.7A www.selectsolar.co.uk 01793 752032 However a vehicle alternator will only manage to get to around 70%. Solar panels come with different ratings that can be 10 W, 100 W and even more. A single solar panel of 280 watts will do the work for you. Secondly, how many solar panels does it take to charge a 100ah battery? A rough estimate is a 20W solar panel for the first 120Ah of battery capacity assuming that the solar panel receives some direct sunlight at least 6 hours per week. A 100 watt panels will be standard size that can be used and installed easily. The 1500mA panel can provide enough power to keep a large bank of batteries topped off, assuming there are no loads on the batteries other than self-discharge. A charge controller is recommended (necessary for gel-AGM batteries). Also if you are charging your battery from your solar panels, you need to ensure your solar regulator is up to the job. Hi Jane, this will certainly work. How many solar panels you need? The higher the watts rating larger will be its size. First, the notes: We hope this solar calculator will make sizing your panels and batteries a little less painful. Keep in mind that this is only a calculator, and it will directly reflect whatever you, the user, inputs into the fields. A 150mA solar panel can maintain a battery up to about 75Ah. Do you need a … (A solar panel at the ideal temperature and aligned with perfect sunlight) Similarly how much power flowing out of the battery can be also measured in watts. Solar Panel Calculator Notes and Instructions. Volts - the pressure of electricity being produced by the solar panel, similar to the height of water stored in a water tank: the fuller the water tank is, the more water pressure you have. And here's a quick tip: We don't recommend to discharge your battery anymore than 50% a day. • Your battery size needs to be (43 x 7 x 2)/12 = 50Ah. This ensures best battery life. That’s about the size of the battery it can maintain. 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