[amc]

I've just bought one of these battery solar trickle battery chargers for a tenner http://www.maplin.co.uk/module.aspx?moduleno=98358
as part of my new home shed and allotment caravan mini solar lighting system along with a 5 quid 12v car inspection flourescent lamp.

The previous owner of my allotment  shed left a couple of dozen 12v selaed lead acid batteries (the sort that provide back up for burglar alarms etc) with capicities from 1.2 - 20Ah. I've had a 2Ah one on solar charge for a couple of days and when contacted to the 12v lamp result! We have light

Some of the batteries are cleraly not safe to be charged and will disposed of correctly at the the council run tip in their "lead acid battery box".

As the output of the solar charger is very low (1.5watts in full sun) it won't charge say a10Ah battery that is flat. How do I test a battery that is flat to see if is in a state to be re-charged? Can an ordinary car battery charger be used to charge them up intially without me blowing up the batteries? (You can get proper chargers for these batteries but they cost about £40)

I may in the end just buy a new battery in the 10Ah range for a tenner to save any aggro.

Thanks
amc

[pairofacres]

Most car battery chargers will be too large to charge something in single figure Ah rating range. If you can lay your hands on a CTEK car charger, their smaller models will cope with 1.2Ah minimum rating. If you use a regular charger on a small sealed lead acid, there's a risk of explosion, so use care! Otherwise, small 12v lead acids are sometimes used in model boats, so might be worth seeing if a friend or neighbour has anything appropriate! There's not really any easy way to check that the batteries are OK, other than charging them for a prolonged period and seeing if they hold the charge.

[Bigbadfrankie]

I have several solar panels. The 1.5watt ones do little to nothing when you consider 12v large battery (10ah+). I used a 60watt one this week end with my caravan and it kept the battery charged even with the tele on. It seems very important to point it at the sun. Lying down it gives aout 2amps, but using a ameter and pointing it at the sun it generates well over 3.5amps.
Your batteries will probably be gell. So try to keep the terminal charge voltage to around 14volts. The liquid acid type can go to 14.4 volts. They shold show around 12.7volts after an hour or soafter coming of charge, if fully charged and hold that for a couple of days at least.
LED lighting helps a lot as it uses so little power.