ASK & DISCUSS INDEX

7 years, 2 months ago - Paddy Robinson-Griffin

I don't, but I'll advise that you need to carry pretty hefty panels to get any real current, and you'll really want some kind of back up. An overcast day can really screw you up!

How big do the panels need to be? If you can indicate the batteries/kit you're powering I'll have a go at doing some maths for you, but when you think cheap/simple solar garden lights can run a 3V LED at about 5mA for a few hours after a full day's charge, it could be pretty big. Of course those lights aren't great cells and not hugely efficient, but they're indicative. If you want to run some numbers yourself, a square metre of panel potentially could produce 1kW if 100% efficient, but they're about 15-20% efficient, so let's say 200W per square metre. That's pretty good still, plenty to change a mobile phone, but it's the big camera batteries that would concern me. If you could buck/boost the output to the required pack voltage (maybe 12v/14v?) you could get maybe as high as 85% efficiency, so peak sun may be good for 170 usable Watts per square metre, and from there it's up to the charger efficiency. You'll probably get full output for say 6h per day, so let's say overall you'll get about 1kWh in a day of usable power. That could also be delivered in about 20 minutes by plugging in to the UK mains, for context. If you've any option of paying a cafe to let you charge for an hour, that may be more effective, but in fairness that depends on charge rates, so things get increasingly "it's complicated"! :).

A square metre is quite a big panel to carry, perhaps look at multiple smaller panels. You lose a bit of efficiency by getting away from the glass ones, but a lot more practicality if they're still rugged. You might get an array of smaller panels, perhaps even roll up ones, and just carry more to offset any efficiency losses.

Anyway, sorry, totally didn't answer your question, just a heads up that it may not actually have a good answer for the above reasons. Solar is oversold for a lot of applications, and frequently doesn't perform as well as you'd hope/is claimed for ideal circumstances. It's worth building a back up plan into your venture. It sounds amazing if you're going off piste, looking forward to seeing your results!