[PhantomGremlin]

Sure, Musk makes it sound sexy, but do we really need to use Lithium in a stationary application? I'd probably be happier with a battery that weighs twice as much but costs half as much. Those might not be the exact tradeoffs, but that's the general idea.

However, I don't know much about the details of battery technology, so I could be completely wrong. If traditional technologies such as lead-acid were up to the task, then someone would have already made a big business out of using them. Does that make sense?

[offgridquest]

Lithium batteries are not only lighter, but smaller. The typical home today to go off grid in the U.S. is a tiny house or a motorhome. The reason is, it's very cost prohibitive for the amount of power you need. Batteries are the most expensive part of that equation. If you live in a 3000 sq foot house and run a $250 per month electric bill, it might take 50 $130 golf cart batteries to power your house for a day or two, and you replace them every 4-5 years. Or you could go with Iron Edison batteries that should last a lifetime. They are equivalent to about 4 golf cart batteries, and the only requirement is to re-fill them with liquid. They cost about $4,000 each, and are yet still very heavy. The lithium batteries will take up about 1/5 the size and even less weight, and should last much longer than the golf cart batteries, but not as long as the Iron Edison. But space and weight requirements down so much will bring down costs with overseas shipping and trucking bills to a minimum compared with the alternatives. Think what great success in small batteries has done for cell phones. Not that your home needs to be mobile, but I see cars with solar panels and homes with solar shingles... both always charging.... as a great use of the sun as an energy source.

[yourapostasy]

Is that $4000 figure for the 12V battery made out of 800Ah 1.2V cells, rated at "400Ah @ 5hr, 450Ah @ 20hr" shown on their web site for $3880? I've always wondered why more fixed site solar PV systems do not use iron nickel technology; it it is initial cost, I wonder what makes this technology so expensive.

Some day I want to look into the feasibility/advisability of a continuous automatic feed of distilled water to keep iron nickel batteries constantly topped off, and a hydrogen outgas capture mechanism (preferably passive) which takes that output of the iron nickel batteries and feeds it as the input into a hydrogen cell.