lowest hanging fruit re: open source batteries

This is an edited version of an email that I sent to Gregor recently.

I'm of the opinion that Ni-Fe is not the lowest-hanging fruit. The internet hype on Ni-Fe doesn't add up. Changhong DoD and voltage parameters are basically the same as industrial lead-acid. The warranties do not cover infinite lifetimes, and no one has proven with any third-party confirmation that their NiFe's work for even 10 years. Surely such long-lived batteries exist, but it took Edison more than 20 years and millions of dollars (those are ~1910 dollars!) to achieve what he did, and Changhong are not Edison cells.

I think we could make lead-antimony alloys, cast lead plates, make lead oxide paste, make sulphuric acid electrolyte, and give lead-acid batteries a user-serviceable/refurbishable form factor. Even if they only last 3-5 years, we can develop the refurbishing process to "renew" them, which would probably only involve removing all the plates, scraping off the passivated layer, squeegeeing on new paste, and swapping the electrolyte. That's less than 1 hour of work for a 1kWh capacity battery, and for me that would mean 3-4 hours of work every 3-5 years -- no brainer even at 100 hours of labor over 20 years.

Decent lead-acid batteries retail for less than $600/kWh over 20 years with 50% depth of discharge: trojan-t-105-re-deep-cycle-battery

That's 6V * 225AH = 1350 Wh capacity, * 2 batteries = 2700 Wh capacity at 100% DoD or 1350 Wh at 50% DoD; 10 year life means 4 batteries in 20 years * $188 cost per battery including tax = $752 for 20 years of storage power for a household that uses a little over 1kWh per day.

These batteries weigh 67 lbs each. That's 268 lbs over 20 years. If they were solid lead, that would be 268lb * commodity price of $1/lb = $268 of lead. The actual quantity of lead is probably less than 70% by weight, so less than $200 in lead for $752 retail pricetag. So they jack the price 3x over commodity value (which itself is 3x over scrap lead value of ~30cents/lb). For me this all completely justifies home-manufacturing of batteries, as I make less than $5k/yr, and the prospect of decent lead acids actually lasting 10 years seems a bit far-fetched. Projected labor time of well under 100 hours for each 20 year timespan.

And lead could conceivably be 3D printed if people want to go that route!

If lead-acid is determined to be just too hazardous to work with (though I presume the lead exposure is similar to that experienced by gun enthusiasts who cast their own bullets, and will be left to old men for whom toxicity is a relatively minor issue), then there are still several other chemistries that I would consider before Ni-Fe, namely: sodium-ion (Aquion, retail $700/kWh), soluble lead flow battery, zinc-bromide flow battery (retail $900/kWh), vanadium redox flow battery, and so-called iron-air cells (in fact, there are a whole class of metals other than aluminum and zinc that can interact with oxygen to store electricity -- probably any metal that can oxidize!). If we had a way to smelt aluminum oxide into elemental aluminum, then an aluminum-air battery would make sense, but I've never seen it done except on a huge scale with free hydroelectricity and cryolite flux -- even more toxic than lead! It's possible that we could develop an on-site recycling process for zinc-air batteries but working with high-temperature zinc is deadly dangerous.

More importantly, we've had lead-acid batteries since the mid-1800s but THERE ISN'T A SINGLE INSTRUCTABLE OR VIDEO OF PEOPLE MAKING THEM AT HOME! There is a video of a Nepali dude refurbishing some car batteries, but that doesn't show us everything, namely plate pasting and the end-product's performance characteristics. We MUST free this knowledge for everyone who might want it. :)

A. J. Tarnas (talk) 20:55, 1 July 2014 (CEST)