I have been asked to check a load of those solar powered lamps that come with spikes for sticking into the garden. Some have leaked but most seem to have completely dead batteries. Problem is I don't have any ni-cads, only nimhs, will these charge in the lamps or do I have to buy new nicads? It would be just as cheap to buy new lights and bin the old lot in that case but I hate to throw away repairable stuff, seems such a waste. Any thoughts?
Bob
Replace them with NiMH, I've done it with a solar lamp and two wind-up radio's, and they work fine. The problem is that the supplied batteries seem to be rock-bottom quality to keep the cost down, they have a very short lifespan, and fail to hold a charge after not many cycles IME.
Replace them with NiMH, I've done it with a solar lamp and two wind-up radio's, and they work fine. The problem is that the supplied batteries seem to be rock-bottom quality to keep the cost down, they have a very short lifespan, and fail to hold a charge after not many cycles IME.
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Also bear in mind that NiMh can have as much as 2 to 3 times the capacity - especially compared to cheap & nasty NiCd cells.
At very least they need a full charge before going in, and it might be an idea to leave battery fittment to the last minute before planting in the sunlight.
Agreed. Also use low capacity cells (800mAh / AA) rather than high capacity 2000+, as they seem to have better charge holding and overall lifetime.
I would say *only* compared to cheap & nasty NiCd cells. I've never seen NiMh anywhere near 2 or times the capacity of a decent NiCd.
How does that help? If the charge used overnight cannot be replaced during the day they *will* run down, regardless of the capacity.
MBQ
I would say *only* compared to cheap & nasty NiCd cells. I've never seen NiMh anywhere near 2 or times the capacity of a decent NiCd.
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But we're only talking about cheap & nasty NiCds because that's what they put in cheap garden solar lights.
Last NiMh I bought from Lidl AA size rated about 2200 or 2400mAh (and I suspect their budget offerings are obsolescent capacities).
Recently I was searching the junk box for NiCds and found a few Saft (supposedly good brand) rated at only 600mAh - so on paper that's 4x.
My reason for wanting NiCds was to replace the one's in my shaver - I conducted various bench tests with both NiCd and NiMh cells that I had to hand, for comparative running time tests 2200mAh NiMh cells ran almost 3x longer than 800mAh NiCds, but the NiMh batteries didn't cope with the higher current draw of actually shaving - I only got 5 shaves compared to about
15 - 20 from new NiCds.
How does that help? If the charge used overnight cannot be replaced during the day they *will* run down, regardless of the capacity.
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Takes longer for the net deficit to accumulate - hopefully you get a few gloriously sunny days before they get dead flat.
Interesting, that - I saw a battery supplier's site where that sort of capacity was recommended for DECT 'phones, rather than the cells of 3x the capacity.
Cells such as Eneloop low-self-discharge have lower capacity but much lower internal resistance, so the high current isn't wasted so much on heating the cell itself.
I think really you could use any old things in this app.
NT
I have just replaced 6 cells in mine. You just need cells that don't suffer voltage depression (memory effect) as they get short charges in winter and long charges in summer and you don't want them to lose capacity through repeatedly short charging them in winter.
I put some Duracell rechargeable in as I get them cheap (4AA + 1hr charger for £1 when Staples stopped selling Duracell stuff two weeks ago, everything was priced as £1 so some stuff was a better buy than others). I don't really expect them to last any longer than the originals.
NiCds suffer the memory issue, but are fine for the job. Memory effect is much overhyped, IRL its seldom a problem.
NT
So with an external short circuit they are more likely to provide enough current to start a fire?
Bill
I think you will find that its a problem on solar lights as the solar cell is never big enough to fully charge the battery and its capacity just gets lower and lower. They seldom last two years, I expect nimh will
They're made in countries where the sun shines. For the UK market they'd be better with a little rainwater driven bucket wheel.
Bill
Don't waste your time. Chuck the whole lot in the bin & use low voltage lights.
Bullshit. Perhaps you should try telling that to the NiCds I've owned over the years.
The varying charge discharge levels due to variations in weathjer and day.night length mean that you are unlikely to see memory effect in this application.
MBQ
e:
Perhaps you should try getting a clue, and a decent charger.
MBQ
Cabling is a pain though.
Mine use 4xAA packs, with NiMH charged in the house beforehand. They're only put out for barbecues.
Not last month.
Isn't it against the Geneva Convention to have to get the garden hose out in March?
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