How to keep my emergency lanterns charged?

Other Hardware General Electronics
1

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:

![](http://www.gammon.com.au/images/Arduino/Battery charging instructions.png)

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?

2

You might want to google for automatic battery float charger like below and see what appears I assume the normal charged battery voltages is ~6v. You might get an inexpensive trickle charger (bottom) and drop the 12v down to near the required voltage for the battery you have by putting diodes/LEDs in the current flow path. If you have two batterys, put them in series and use the standard 12v battery trickle charger.

https://www.google.com/search?hl=en&as_q=automatic+battery+float+charger+&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=&as_occt=any&safe=off&tbs=&as_filetype=&as_rights=

3

These lanterns have a base that you have to unscrew, then four more screws to take out a retaining bit of plastic, to get at the actual battery. So if I remove the battery and put it on a float charger it isn't really ready for use in an emergency, although I suppose I could reassemble it (them) using a torch.

4

DIY?...

Drill a hole, add a couple of wires to a connector (your standard, plug in toy type ( () ) connector (where you just drilled a hole or two) and then simply have a couple of wires leading from the battery terminals +/gnd to your, then do the same the other end but a cable that plugs into that and hooks up to your float charger, that way you can not only leave it on float (because there's no regulation in the emergency charger) and when the power goes out, you know it's fully charged, unplug it and go no mess....