Lets talk batteries.
Does anyone have a favorite battery chemistry that they are using for their solar setup? In the past I've purchase AGM lead acid, only to have them go dead when I forgot to charge them up before storing them. And because they were AGM, I couldn't replace the acid or break up the sulfates. Plus they are heavy and if I'm not mistaken you should only really run them down 20%, which means there is a lot less useful energy then what I'm banking on.
Lately I've been using a variety of Lithium-ion. I have a variety of portable tools that use 36v Lithium Nanophosphate batteries made by A123. These are great...unfortunately they are hard to come by as far as I can see A123 went out of business.
Next I tried out Philips 18650's. I have a few 75watt battery banks that I've put together. So far so good, but I have this lingering fear that a poorly made battery management circuit is going to cause a fire. I do like that I can discharge them to nearly zero without damaging the batteries.
I was briefly stoked on Nickel Iron batteries, as they are supposed to last 30-50 years...but they don't appear to be that efficient, and they self discharge pretty quickly.
I'd like to take the plunge and build a 1kW battery bank, but I'm not sold on any one technology as of yet. Anyone have experience they'd like to share, or a well thought out opinion? Any open source battery management systems for Lithium ion?