This has been known to cause solar charge controllers to switch to their maintenance mode even if the battery isn’t fully charged. Also, remember that too much current can cause feedback in the battery. I would suggest looking to a smaller solar panel. Given our panel ratings, you would most likely need to step down to 80 watts or less if you were using that small battery. Since our 100-watt panel puts out over five amps, I imagine it would be too much for that small battery. For an 18 AH battery, that would be 4.5 amps or less, so you must check your solar panel’s max amp rating. Most manufacturers will use a rating term max charging current or have a grid that shows the Charging Voltage Range with an Initial Current Rating. You would have to check with your battery’s manufacturer, but the initial start-up amperage may refer to a discharge rating, not a charging rating. Look at our solar page, pick a panel you like and then enter the watts here.Īs a general recommendation, we typically recommend charging a battery with an amp rating of 25% or less of its AH unless otherwise stated on the battery with a different rating. Field #25 is just like field #18 in the battery section. We will then automatically guesstimate for clouds, bad weather etc. How many hours of direct sunlight do you estimate your panel will get. The last two fields, #22 and #25 are easy. We don’t like to see any battery discharged more than about 50%, so we will automatically adjust for that. Say you want to use a 55 AH battery because you like the dimensions, or maybe you like the 21 AH battery due to its terminal configuration. Field #18 is based on what battery you choose. This is minus any solar panels, which we will figure in a minute. In #14, insert days of backup you would like your battery pack to be good for. (22 x12 =264 watts)įields #6 and #12 are for how many hours you expect your equipment to run in a 24 hour period, and your input voltage (12, 24, 36?).įields #14 and #18 will determine what size and how many batteries you need. (example, 2AC amps =20DC amp)ĭC amps x 12v = DC watts. To get there, use the following formulas ġ Amp AC = 10 Amps DC. Then you will need to add about 10% due to the inefficiency of the power inverter. If you are using an DC to AC power inverter, meaning your device is rated in AC amps and 110 V, you will need to convert that number into DC watts before entering it in the field. Now the instructions:įield #3: This field needs to be DC watt draw only. Normal RMA and exchange rules will apply to all solar panel purchases. is in no way responsible for the results of your calculations, and if you purchase a system based on the results of the Solar Calculator, BatteryStuff will not and cannot be held responsible for returns or exchanges for improperly sized systems. This calculator is for educational purposes only. With that said, here comes the disclaimer. If your base calculations are off by even a little bit, the results reflected can be skewed by quite a bit, so view this as a guide, not an absolute. Keep in mind that this is only a calculator, and it will directly reflect whatever you, the user, inputs into the fields. For help using this calculator please read through our detailed instructions.įirst, the notes: We hope this solar calculator will make sizing your panels and batteries a little less painful.
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