Solar light batteries AA 600m 1.2V?

[milkeybar kid]

Help please, has anyone spotted these in a shop. We have tried Auchan, Gamme Vert, Terre de Sud!!Intermarche, Briconaute, Bricomarche.

Some of last years solar lights are tired , tested them with a normal re charge and they are all OK but of course the solar panel cant charge anything above the recommended AA 600m Ah 1.2V .

I see loads on Amazon etc but would prefer to buy locally...... any idea please. Thank you. MBK

[cooperlola]

We just replace ours with standard re-chargeable AAs from the supermarket (top of P2, link below).   They last for years, unlike the silly things that come with the lamps in the first place.

http://www.auchandrive.fr/magasin/laRechercheExpress.jsp?search=simple&textSearch=pile&x=17&y=4

But they are cheaper from Amazon.

[Pierre ZFP]

[quote user="milkeybar kid"] but of course the solar panel cant charge anything above the recommended AA 600m Ah 1.2V [/quote]

Um yes they can.  The batteries just won't necessarily be charged to their full capacity.  This year when some of mine had failed I replaced the 700mAh batteries with cheap 2000mAh ones and they work just fine, better even than the originals.

[milkeybar kid]

Thanks for the replies, phew, I will buy what you recommend!

[AnOther]

I think you misunderstand the theory behind rechargeable batteries and their charging.

The charging of Ni-cad and NimH batteries is by a constant current and is controlled by their voltage or their temperature. For a single cell the voltage rises to a nominal 1.2v at full charge regardless of rated capacity so a battery of say 1000mAh will take twice as long to charge to full capacity as one of 500mAh but the charger for both will be identical. In multi cell batteries the temperature is also monitored and if that rises above a preset level before the battery has reached 1.2v x however many cells the battery contains then the charger reduces the current or shuts off altogether.

In your garden lights then any capacity of battery will work however for maximum life you should choose one which suits the purpose, i.e. one which will fully charge during the day and fully discharge during the night as this is the sort of cycle they are designed for and thrive on. Putting in higher capacity batteries which only partly discharge and then top up in the day is a waste of money and will hasten their demise unless you take them out from time to time and properly excercise them to their full capacity. It's called the memory effect.

So, although there is no such thing as a specific battery for garden lights the ones which are advertised as such are simply of the correct capacity recommended for the purpose.

Unfortunately I doubt anybody ever got prosecuted for optimistically claiming xxxmAh for their batteries which makes choosing them a very hit and miss affair and it has to be said that at the price they are sold for cheap solar lights cannot possibly contain quality batteries so are unlikely to last more than a season and when replacing them it's best to go for go for known brands at the capacity stated for the light.

As an aside there is a school of though which says that it's impossible to achieve

some of the capacities claimed, 2300mAh for instance. To genuinely draw

2.3 amps for an hour out of a tiny AA battery would cause it to get so incredibly

hot that it could easily melt the plastic of whatever it was being used in and destroy itself in the process !

[Rabbie]

[quote user="AnOther"]As an aside there is a school of though which says that it's impossible to achieve some of the capacities claimed, 2300mAh for instance. To genuinely draw 2.3 amps for an hour out of a tiny AA battery would cause it to get so incredibly hot that it could easily melt the plastic of whatever it was being used in and destroy itself in the process ![/quote]Just because a battery has a capacity of 2300mAh does not mean you can draw 2.3 amps out of it for an hour. it should mean however that you can draw 23mA for 100 hours 

[cooperlola]

All I can tell mbk is that the rechargeable AAs which I bought on the internet 3 years ago are still in our (cheap French brico) solar lights and they still illuminate every night.  The technical stuff, well, zzzzzzzzzzz  Sorry, Erns![:D]

[AnOther]

Agreed that in practice capacity is nominally measured at the C/10 rate (230mA for 10 hours) but even so, if there were a genuine 2300mAh AA battery, and IF you could control it's temperature, then you should be able to get 2.3A for an hour out of it - or more.

Have a look here, http://www.batteryjunction.com/oneni721bapa.html it's 6 cell pack for the higher voltage but it's made up of individual 2200mAh cells in series.

Note the recommended maximum discharge current of 30A, that's an overload factor of more than double so with that sort of load the pack will last for under 30 minutes !

Apologies Coops [:D][:D][:D]