Solar panel for power station (North UK)

[Mark2022]

I've just purchased a Swarey 240W power station from ebay for £90 and I'm wondering whether it would be worth also buying this solar panel kit considering I'm in the borders...

https://www.ebay.co.uk/itm/394808275047?hash=item5bec683067:g:ChkAAOSwECxkPPQ7&amdata=enc%3AAQAIAAAA4JfvgacWNaX79H5Kqs%2FuDnqiQZ8BghNGxd66pWus%2BZZiehDwscyD6tyB2tvtnDerLUv966dTpEmbaNWw9%2BEhfzXgXLlNc1FwllLkotOoOLAZm2obyytw%2FREBC7ZjQGaLFCvCX9RlQ1DqzNytZilp16eNMOCD%2BeLawNi4jbya%2B1LNWMOPuytBdA1Ci4cdid0vfNSQ50TEdEakhJKZGvqaAlcuZcRnViBU8Ru5DlG1XTNusA6atJLjhZxhn3azphCJ0Dbp0%2BEqgPbgdaokhyssrw8bQhEcLjaMTVOXNv9rRgbo|tkp%3ABFBMqPTiitdi

I'm just finishing off the build of a small observatory/shed - a copy of Skipper Billy's "Flip Top" design - and it is built atop a car port which provides me with a 5x5M space which is enclosed by my house wall (with a door out to it from my first floor landing) and my neighbour's which means I am blocked from looking South/South west (but I just catch the meridian) and North/North East (but I can still see polaris. 

What I do have is (once I clear the neighbour's roof across the street which blocks East to South until about 20/25 degrees altitude) is a clear view of much of North East to the south meridian and, for the purposes of having power on the 'terrace'/roof of car port, I bought the power station but I'm interested to know if anyone in the north has done this while also having a portable solar panel to charge the power station at least some of the time?

A few photos of the build if it interests anyone. Completion, hopefully, by the end of this month. I can assure you it isn't as perfect as "Skipper Billy's" but, by the time I'm finished with it, it will be sufficiently waterproof. The roof already is but, as for the walls, because I used wood from a neighbour's old shed (mostly anyhow to keep costs as low as possible) and due to me not liking overlapped wood on the walls, I'm filling lots of gaps and cracks with good quality sealant.

Anyhow, anyone in the north (i.e. north of, say, Blackpool) who has tried the solar panel supply to a power station, I'd be interested to hear your thoughts.

 

[Mark2022]

How long would it take (on a nice sunny day, anywhere between May and October) for a rated 100W panel (assuming the 20% efficiency and that it truly is 100W) to charge a 240W power station from zero? Again, talking about 55deg latitude. Seems a simple question but it's not because you have to factor in that irradiance at such a latitude, the efficiency and, possibly, other factors. I'm just looking for a finger in the air sort of answer though. Could it be 2  hours? 4 hours? 8 hours? 2 days?

[StevieDvd]

Accoroding to Jackery

"The Jackery Explorer 240 Portable Power Station can be charged within 5 hours with a SolarSoga 100W solar panel."

So figure that's based on a US sunny day, and a for UK day I guess it would be twice that at least.

 

 

[Mandy D]

3 hours ago, Mark2022 said:

How long would it take (on a nice sunny day, anywhere between May and October) for a rated 100W panel (assuming the 20% efficiency and that it truly is 100W) to charge a 240W power station from zero? Again, talking about 55deg latitude. Seems a simple question but it's not because you have to factor in that irradiance at such a latitude, the efficiency and, possibly, other factors. I'm just looking for a finger in the air sort of answer though. Could it be 2  hours? 4 hours? 8 hours? 2 days?

You don't need to make any assumptions about solar panel efficiency as that is already baked into the specification. If it says 100 W, then that is the rating under the clearest skies, with the Sun as high up as possible and the panel tilted orthogonal to the rays. However, if the rays are hitting the panel at an angle and you can't tilt it for whatever reason, multiply by the sine of the angle, e.g. at 45° this would be 1/√2 (approx 0.707). For sensible angles you can ignore the extra atmospheric losses, these become more significcant the lower you go. Also, latitude really does not come into the analysis. It is about the angle of the panel to the Sun's rays.

So, the output is going to vary from maximum down to very little depending on cloud. At max output, assuming the battery can absorb the available energy and assuming a charging efficiency of, say, 75%, you will want 320 Wh into the charger to take it from flat to fully charged., so about 3 hours 12 mins with a 100 W panel. That is about the quickest you could expect. In reality, on a clear summer day it might take 5 hours. On a grey winter day you will have to allow much longer, probably 5 - 10 times.

It is very much a suck it and see thing. But those should be reasonable guidelines. This seems to be roughly in line with the Jackery advice posted by @StevieDvd, above.

Edited September 22, 2023 by Mandy D
clarification

[Mark2022]

Thanks guys (and girls) for your input. It might still be worth it even if it takes a couple of days to charge since you and I both know we're not out there every night (chance would be a fine thing) so i guess there's no rush.

Americans huh? All that damned luck! My pic is taken at the summit of Pike's Peak, Colorado Springs (14,000 feet). The weather and the terrain they have over there is annoyingly superb! 🙂 Snow, cold but warm up there all at once! Very odd.  Now imagine a big SCT or something similar!

[michael8554]

Hi Mark

Just for clarity, the capacity is 240 Watt-hours, not 240 Watts.

240 Watts may be the instantaneous peak power output.

I like Mandy's Real World assessment.

If the power station is a decent design that protects the battery life, you could leave it trickle-charging until you next need it.

Michael

[Carbon Brush]

Another vote for @Mandy D assessment. Yes you only get the rated power under exceptional circumstances.
The long term average power delivery is a small fraction of the rated power.

Referring to @michael8554 comment.
A lithium charger MUST shut off when it determines full charge, and have a safety timer.
If these are not in place, refer to many online videos from security cameras that show ebikes and the like exploding when left on charge.
Sorry if this sounds like a rant, but having seen too many poorly designed and dangerous lithium applications, often carrying fake or inappropriate safety approvals, warnings are essential.
I never allow unattended equipment charging unless I have confidence in the manufacturered product and the approvals paper trial.
 

[michael8554]

No way a rant.

I agree, I shouldn't have used the words "trickle charge".

I should have said "a decent BMS for the battery should allow it to be left plugged in without overcharging."

Michael