Well, here I am, trying to take a photograph of what it looks like when doing routine battery maintenance. A word about battery maintenance: This is perhaps not an ideal situation in which to pick up a mating partner unless, of course, you stumble across a prospective companion who is turned on by protective eye wear, rubber gloves and a headlight.
That headlight thing is to be able to peak into the holes of each cell to see how much water you need to add.
"Battery maintenance" involves mostly adding completely sterile water in each little cell, and occasionally rubbing the knobs where wires are attached with a little petroleum jelly. This is not something I've discovered myself, of course. I've just read a million times that this prolongs the life of the batteries, and in general makes them work better. Not only solar power weirdos say so, but car people too. Millions and millions of grease monkeys and shop owners and automobile fanatics. So I'm taking a wild chance that all these people know something I don't.
This is, however, one of those things you can never, ever suggest anybody else should do. I know a number of people with small solar systems in summer houses or remote skiing cabins, and usually they have spent weeks and weeks of wages on a system that ends up powering two measly small lamps a couple of weekends a year.
And they have never, ever added water to the battery. Usually they seem to never even have heard of the concept, which is interesting as almost all of them have cars.
I am not such a genius when it comes to taking heed of advice myself. This is probably an evolved chimp-thing, a trait most of us share. We will all run around with scissors and jump into the water straight after eating until it kills us.
If sloshing water into the cells does not feel right for you, go for sealed batteries, which are actually, and incredibly, just about as maintenance-free as the people who make them claim. But if you, like me, go for the batteries that look sort of like car batteries, fill them up every now and then, until the liquid almost reaches the bottom of the vent well. It's hard to say how often this should be done. I haven't done it for half a year and boy, I should have done this a lot earlier. And only use absolutely sterile water, and (not shown) an absolutely clean funnel.
There are automated systems for watering batteries, too. This can make some sense, but also looks suspiciously much like just yet another doo-dad.
Update: Read the comments. Turns out rubber gloves and distilled water are more optional than I thought.