kowtow wrote:This has been a great forum to indulge in.
I'm posting to get some ideas about what I can "practically" speaking, expect from my solar panel configuration.
I have two 100W solar panels (200 watts total) with a cheapo PWM charge controller. My batteries consist of four Costco (#12852) 12v 115Ah batteries connected in parallel for a total of 460ah (conservatively 1/2 of that to be used before requiring a charge). I also have a 2.5kw DC to AC inverter for any AC that may be required.
Aside from all the "what's the power drain, blah, blah, blah" stuff that I can calculate on my own. I want to get someones advice on what a system like this will do to charge up my batteries from a drained state (50% of max capacity). I can calculate the numbers, but I would like to understand from someone who's been on the playa, what can one really anticipate in terms of hours of direct sun in general and what the charging efficiency is (I know that's a very general question) of a 200 watt system in terms of charging up this bank of batteries.
Let me take a wag at this. YMMV. But at least it's based on a little experience.
On a good day on the playa you should get about 165-170 peak watts out of your setup at the panels at high solar noon. (The "rated" watts are a lab figure, in perfectly clear and cool weather, at the equator, perfectly positioned, at high solar noon, and you won't ever hit this for very long). Next you can figure-in a few watts lost in the charge controller, and then quite a few watts lost due to battery physics (call it 15%). The length of light that is usable for solar generation on the playa is about 11 hours. So as a guess I'd figure 120 average charging watts per hour over 10 hours, for 1200 watt-hours/day. At 100 watts/hour in a 12 volt system, you're charging the batteries at the rate of 8.3 amps/hr, so call it 91 ah/day. So to take a battery at 50% capacity to fully charged you're looking at somewhere around 2-1/2 days.
Captain Goddammit wrote:Usually someone chimes in saying charging at a very high rate is bad for your batteries... I say bullshit, I use those same batteries in my MV and they get charged by a pair of alternators at between 50 and 100 amps. Every battery installed in a vehicle gets charged at pretty high current.
So, I'm recommending getting as powerful a charger as you can, and do the solar just for the sport of it if you like. Electrically, it's a drop in the bucket.
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