Solar lights

[JohnP]

SWMBO want a string of solar lights in the garden. I have noticed some have ena,elled copper wire rather than the more usual plastic covered wire. Any thoughts?

[charles]

I've had enamelled wire lights up at Christmas. The wire hides quite well in tree branches. It all depemds on what you want.

[Harry Bloomfield, Esq.]

JohnP used his keyboard to write :

Don't expect them to operate for long, after dark in the summer and probably not at all in a UK winter.

[fred]

I.M.E you'd be lucky to get 12 months out of them

[NY]

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.

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.

[Adrian Caspersz]

Overcharging can damage the cells.

[Theo]

Solar lights require a long cycle life (one charge/discharge cycle a day). They're also repeatedly cooked and frozen. This is about the worst situation a battery can be in. It is better to put in a lower capacity cell that's more robustly constructed than a cell with maximum capacity that's rarely going to be used, but is less able to withstand the harsh environment. Carthorse v thoroughbred.

The cells probably work less well in the cold.

Theo

[Fredxx]

That may be true for some battery chemistries but not most. For example, lead acid last longer if they don't undergo a deep discharge.

Solar lights will typically flatten its battery during the winter. I would suggest the choice of battery chemistry is critical.

I would have thought the opposite, diodes have a sharper IV curve at lower temperatures and reverse current leakage would also be lower.

[Andrew]

Should deter slugs :-)

[Theo]

When people say 'solar lights' they usually mean the plastic sticks with a small solar panel and a few NiMH cells. I've not seen those use lead acid.

I meant the battery cells. The panel itself is happy in the cold (ask every satellite).

Theo

[Martin Brown]

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.

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...

[JohnP]

I would really like some that had a timer - I could turn them off when no longer appreciated to save flattening the battery every night.

[Peter Burke]

JohnP [e-mail] wrote in news:XnsACD860D76B6E8JohPnowherecom@81.171.92.222:

You'll need to roll your own then, decent panel (choose your angle), charge controller (includes timer), SLA battery, low voltage cabling, marine box. I've recently put in some non-solar using cheap GU10 spike lights but with low voltage GU10 lamps instead of mains, very effective but the cabling is an obvious overhead.