Do these solar panels look any good?

[lux1moonprince]

[CharlesHarris]

[CharlesHarris]

Error step 3 should be
40% DoD:
18,000 / 0.4 = 45,000 Wh

the 18,000 carried over from step 2

Just looking to see if you were paying attention 8-)

[Mortblanc]

All that and no one noticed that they are USED panels.

No indication of the age, length of use, or for what shortcoming they might have been returned to the mfg for resale.

I think you can get a better value for your money.

[harrypalmer]

"These panels are working perfectly. There were installed on a solar farm, half of which was damaged in a hail storm so the insurance company is paying to replace the whole installation with larger 260W panels. These are the panels which were not damaged in the storm, and are all working 100% and only been installed for a few years. The output on these panels is fine, but some of them have a cosmetic issue called "snail trails" where there are some silver trails across the cells. This does not affect their performance, its purely a cosmetic issue and we have tested them to confirm they are fine. "

[Lightspeed]

Answering OP specific question

Calculate just 10% of solar cells' rated output in midwinter, although you'd still expect around 4 hours a day output at this time of year.

You'll also a need an invertor to convert 12v to the 240v that your mains chargers expect to see. Invertors frequently run at just 50% efficiency so you have to input twice as many watts of energy at 12v than you'll be getting out at 240v.( if that makes sense?)

Assuming a lap-top charger of 65w and 3 phones charging at 5w each, and all of them plugged in for three hours charging per day, by my calculation you'll need 7 x 175w rated panels to do the job in deepest winter, and conversely, these will of course be generating 90% over charge in the summer months so you'll need to decide what you'll be doing with that spare energy.

Another strategy would be to find a more efficient invertor and less device charging time to reduce the required generating capacity. With careful choice of components and non exhaustive demand from the lap-top and phones, you might get away with just three cells.

Don't forget backup batteries and charge regulation to complete the setup.

[LAC]

I avoid using inverters on my system whenever possible, and instead use dc to dc converters to avoid the massive power loss as LS has stated.

I use a 12v dc to 19v dc step up converter to charge laptops that are rated at 19v dc, which most full size ones are. Using this method there is only a minor power loss compared to using a 240v ac converter then stepping back down to dc using the device's local power supply.

For devices 12v dc and below I use a 12v dc to various dc voltage ratings, from 12v dc down to 1.5v dc, and the input connects to my battery via a standard male to female cigarette lighter plug and socket set up. The output connects directly to the device's dc input socket using the relevant universal plug adapter and switched to match the device's dc input rating.