Solar Charger Questions - Page 1
Forum section: electronics / general

author: onder
author_rank: Newbie
timestamp: December 05, 2019, 06:18:07 pm
content: Hi All,i havent any experiance about solar power systems. i have a device taking 20Amp at 5V and it must be work all day. i didnt find a right formula to calculate how many panel and battery i need.can anybody help?

author: OpenCircuit
author_rank: Regular Contributor
timestamp: December 05, 2019, 09:29:05 pm
content: Looks like 100 watts to me. Curios what device consumes 20amps at 5v though?

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 06, 2019, 02:28:50 am
content: Does "all day" mean 8 hours per day or 24/7? Is it a constant 20A or is that a peak draw? That makes a big difference.Quote from: OpenCircuit on December 05, 2019, 09:29:05 pmIf talking modern stuff, I would have to guess a bunch of single board computers or a bunch of smartphones/tablets. (Many years ago, it was common to scavenge older PC PSUs with a lot of amps on the 5V for running Perk mining smartphone clusters.) Or maybe even WS2812 LED strips.

author: onder
author_rank: Newbie
timestamp: December 06, 2019, 12:31:59 pm
content: Ouch ... i forgot say its peak current. ~10amp average. it ll work 24/7. i ll use a microcontroller board and 6 x P10 LED pannels.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: December 06, 2019, 02:25:38 pm
content: I believe storage capacity should be three times consumption. Storage capacity is not the battery rating as advertised but the useful capacity of the cells themselves, which varies by cell type. I have found the ratings on many things are higher than actual consumption, so testing with a watt meter that logs consumption over time, i.e. 24 hours would be useful.

author: Seekonk
author_rank: Super Contributor
timestamp: December 07, 2019, 07:47:49 pm
content: Do you have backup? From my experience it will take about 2KW of panels to do that. Of course, you can listen to all the sunny day people. All solar is local.

author: XFDDesign
author_rank: Frequent Contributor
timestamp: December 08, 2019, 04:20:01 am
content: The math should be reasonably straight forward:First figure out your consumption: 5v @ 10A = 50W steady state.Running 24 hours, 50W x 24H = 1200WH.Assume you have a good converted off of your battery, 95% efficiency: you need an energy supply of ~1265WH.For solar, you have to get insolation data to know how many usable hours of sunlight you can get in a day. Suppose it's 8 hours in a day.For 8 hours, you want panels to power your system and recharge the batteries.Batteries supply (50W x (24 -)/0.95 = 850WH of energy.Battery recharging, assuming 95% efficiency, 850WH/(0.95*= 112WWhile that happens, you want to keep your main device powered, which is also 100WNeeded paneling is then: 112 + 100 = 212W.If you want to pad yourself with a few days of operating capacity (covering rainy weather), you'll want to increase the battery operating hours and thus battery capacity. Panel sizing will have to accommodate the battery sizing to recharge the batteries in time. Panels will also increase if you want to pad for off weather / poor insolation.Maybe a 540W system as a medium compromise?

author: Seekonk
author_rank: Super Contributor
timestamp: December 16, 2019, 01:36:44 pm
content: Your results may vary. I live off grid in the summer at camp. At home I have a 520W array for development and testing. Between projects I run the array into a resistive electronic dump load at power point to make heat. Here are my results for the last 2 weeks. Double the results and you are still in trouble. I'm at 41 degrees latitude. Remember, not only do you have to run the system, but recharge the battery.DAILY TOTALS DECEMBER 2019DATE WH 520W ARRAY03 33604 97305 94206 17807 97608 48109 8410 31311 53112 67913 53514 31415 80016 707212 total WH / 14days = 515WH / day