I have some "emergency" lanterns, intended to be used during the occasional power failure. They have SLA (sealed lead-acid) batteries. They are apparently not supposed to be continually charged, nor are they supposed to be completely discharged:
By their nature, emergency lights are not the sorts of things you use every day, so they don't get routinely charged/checked. What tends to happen (to me anyway) is that I remember to recharge them every 6 months or so for a year or two, and then forget about them. Then after two years, when the power fails, they are dead, and their entire purpose is wasted.
There must be a better way, musn't there? Perhaps have some sort of voltage monitoring on the battery terminals, and then, when it gets too low (whatever that is precisely) the Arduino (or similar) switches on the plug-pack to recharge the battery back up to maximum.
Does anyone have any good suggestions or tips about the best way of achieving this?