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[NFMike]

I personally don't use continuous trickle on my SLAs. I recharge after use (with a charger that goes to trickle at the end so it doesn't matter if I forget it for a day or few). Then I take them off charge and check the voltage occasionally with a meter. When it gets down to about 12.6V (for a 12V nominal battery), which I believe is about 70% capacity, I give it a recharge.

Two reasons:
1/ I don't like leaving that kind of stuff live all the time - it's in the house where I and my family sleep.
2/ Cost. Most of these chargers are quite warm in use. I've not measured any but as an example if you say it's dissipating 5 Watts then you can do some math. 365 days, 24 hours/day x 5W = 43,800 Wh. Nearly 44kWh. At current UK prices of around 14p/unit that's over £6 per year. (And it's not very 'green' either     (which is also why new telly's, etc, now have to use <1W in standby))

[grendel]

which is why mine sits on a 1.5w solar panel and stays topped up for free. (plus those panels are at £10 each at maplins at the moment).

Grendel

[HawkEye]

which is why mine sits on a 1.5w solar panel and stays topped up for free. (plus those panels are at £10 each at maplins at the moment).

Now this may be just luck but i had a dead 12v 17ah sla that wouldn't take a charge from anything , I tried various voltage/ currents,so I connected it to a solar charger (Maplin 1.5w) in the greenhouse, this was at the beginning of May, in mid July I took it out discharged it ( hi amps ) by use of an inverter, then recharged as normal.This battery has been in normal use since, at normal capacity  , I wonder if a hot humid greenhouse had any effect combined with a slow trickle charge?.

Tony
 

[grendel]

I have heard that the slow cyclic charge provided by a small solar charger can bring back a sla from dead, and even had it bring one back from a 6.5V condition (12v battery 10Ah) but couldnt repeat on another battery with a similar voltage, so it may just have been luck.
Grendel

[More Coffee]

Its pretty much hit or miss bringing a battery back to life from stone cold dead.
Desulfation cycles help but often the battery dosent respond..
I give the sla's a shake before even bothering with them, if anything rattles around its a good sign its not worth bothering to try, its dried out and burnt.