On 19/02/2021 11:12, NY wrote:
"fred" wrote in message
...
On Friday, February 19, 2021 at 10:02:58 AM UTC, undefined wrote:
JohnP used his keyboard to write :
SWMBO want a string of solar lights in the garden.
Don't expect them to operate for long, after dark in the summer and
probably not at all in a UK winter.

I'm surprised at how small the capacity of the rechargeable batteries
that are used in most solar lights. Part of the reason that they don't
last very long even in summer is that a lot of solar power goes to waste
because the batteries cannot accept any more charge.

They don't do too badly in the summer, but they are designed for a much
lower latitude than the UK and come on in our twilight and have pretty
much given up by midnight when it is properly dark.

Having said that, our lights do last a lot less time in winter, so the
amount of daylight is also an issue. I'd have thought that modern solar
cells would be able to produce usable power even on an overcast winter's
day.

You would be disappointed then. The solar cells on them are typically
the cheapest polycrystalline going and can on a good sunny day manage
about 30mA at 3v output. Total charge is likely to be at most 3Ah/day in
mid summer continuous sunshine and next to nothing in mid winter.

It is an order of magnitude (or two) lower power under cloud. The
combination of cold, damp and being flat for the four winter months
destroys batteries even in professional roadside kit supposedly designed
for the duty.

The radar activated "Please go round the dangerous bend" signs here are
invariably dead in the water on cold frosty winters mornings...

--
Regards,
Martin Brown