We saved money on our solar system up at our “portahut” tiny house by using conventional lead plate batteries that need water now and then, along with what they call “equalization.” The idea is that crud builds up on the battery interior and you zap the things with a controlled overcharge (around 15.5 V) to knock it off, along with letting your charge controller do voodoo that gets the batteries voltage “equalized” so one battery isn’t operating at higher voltage than another and thus constantly trying to charge the lesser battery. The process is supposed to happen once every few months (some say once a month). Our Blue Sky controller can equalize automatically once per month, but automating the process produces lots of flammable hydrogen at who-knows-what time of day. Better to be in manual control and switch on the equalizing when you’re not cooking or otherwise operating a nearby open flame in your “tiny house.” Here is how it went:
I’m still not sure the upkeep and hydrogen venting issues with this type of battery are worth the initial cost savings when compared to sealed batteries. For example, when used during winter in a small cabin, you don’t want to be venting in any way that could introduce hydrogen into the interior of your structure. That means a venting system that works with exterior air, thus cooling off the batteries and reducing their capacity. More, even if you set up automatic equalization for flooded batteries such as ours, you still have to check the water level and clean up acid seepage. My advice is to seriously consider spending the extra coin on maintenance free batteries for this sort of small-scale solar install.
Whatever the case, now you know what’s involved with manual equalization and you’ve got an overview of “tiny house” solar battery issues.