What if Tesla has been storing up a surplus of these things while the grid idea has been under R&D?
Knowing that these cells can be bought at a 7% discount with 8% higher capacity next year? That sounds like a terribly bad idea to me.
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... by using the current cell technology they are using, Tesla can ride the coattails of what is currently a much larger business (consumer electronics) to drive down the cost and improve power / effectiveness of their cells.
I understand that Tesla is having
automotive cells manufactured by Panasonic. Tesla has been doing extensive testing with modified Li+ chemistries and the one most suitable for Tesla is used. I have no idea to what extend Tesla benefits directly from advances in laptop cells (which are never discharged at 4C, for example).
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Perhaps that's the way to charge quicker than filling a tank of gasoline..
I am pretty certain (read: I have no proof, whatsoever) that the cells cannot accept a 20C charge. Multiple connections could solve a power distribution problem but if you can't charge a single cell in 3 minutes you can't charge a pack in 3 minutes either.
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given that a CES solution with batteries would have no weight requirements and are stationary, are the current cells ideal?
Technically: No. Financially: Yes, because over time many, many 70%-capacity cells will flood the market. At that time, say 7 years after manufacturing, these cells only have use for grid-backup as car batteries by then will have higher capacity, lower price and less weight.
Even at 10% of their original capacity these cells will be of (some) value as grid-backup.
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But I'm wondering how difficult is it to theoretically charge at 6c speed?
No biggie. Some Li+ cells can be charged at 20C. The only question is how much damage this would cause to the cells. If only I could get my hands on a new pack I could easily try this out: keep the cell at, say, 25 degrees C (using some liquid bath), charge up to 80% SOC at 6C, discharge at 0.5C, repeat (1000x).
Have a small circuit that does this to 4 cells (to filter out anomalies) at 6 charge rates and come back in 3000 hours (4 months) and I can draw you a nice graph of the damage of fast charging.
Tesla
must be doing this sort of thing 24/7.
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At the level of a single pack, if this electricity arbitrage is worth $0.10 per kwh (say buy at $0.05, sell at $0.15), and if you move 50 kWh/day, then the pack is earning $5/day. [...] But if the packs cost more like $100/kWh to manufacture, then you're down to about 5 years to pay for the pack - that sounds really desirable.
20.000 S-es per annum, 70 kWh avg could in, say, seven years time flood the market with 20.000 x 70 kWh x 70% capacity = 1 GWh every year. That's 1GWh in very cheap cells because not many would want these cells as newer cells are cheaper with a higher capacity.
I can certainly imagine these second-hand packs going for $100/kWh or less by then. I the game of World Domination seven years isn't all that long.
