I have two sealed lead-acid batteries in parallel that have that inscription on the sides.
They power multiple 10W (Actually, 7 on the meter) PIR lights all night long, as required.
That inscription has me confused.
The first part is obvious, 12 Volt, 18 Ah. But why does it say 20 Hr?
My guess is that it is telling me I shouldn't take more than 18/20 of an amp hour, and it will last 20 hours.
So, assuming 5 of my lights turn on, at 7 Watts Each, that would be 35 Watts, divided by 12V would be about 3 Amps.
Going strictly by the 18Ah rating I would expect 6 hours at that rate. (In reality, I never draw that much for that long. It is for young'uns to go to the bathroom at night and things like that.
The 20 Hr thing makes me think that it is a warning that battery damage might occur if I try to use all of those 18 Ah in less than 20 hours.
But clearly my concern is peak power load times. It is possible for all of the lights to be on for an hour or so if the girls get up and work in the kitchen at night.
I believe my best way to interpret this is to keep it on a 2 Amp AC-powered trickle charger at all times, instead of just running the trickle charger off the inverter during daytime when the sun is out.
Agree? Disagree? I haven't used sealed batteries before, so don't know if the constant trickling might exceed that limit, also.