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Printing money is not a great business if the printers cost $10M and they print out $1,000 a day and lose the ability to print after 1,000 printings. The econo

Printing money is not a great business if the printers cost $10M and they print out $1,000 a day and lose the ability to print after 1,000 printings. The economics are still not there yet for widespread battery energy storage. Here are some real numbers: Wholesale prices fluctuate, but are often in the range of 0 - 10 cents per kWh. Lithium ion batteries cost something like $250/kWh. The inverting electronics cost like $100/kW. Round trip charging efficiencies are like 80%. Battery lifetimes are like 1,000 charge cycles. So assuming a system with 10 kWh at 5 kW, your costs will be $3,000. Or, on a per cycle basis, $3. If you charge 10 kWh for free and then sell 8 kWh for $0.10 each, you're making $0.80 on the transaction. Not enough to even cover your $3 in levelized costs. (Obviously the economics improve with better assumptions. But there's still maintenance, interest rates, hookup costs, and destruction costs to take into account.)

mtgx 9y ago
Fortunately for Tesla, it also sells a few more products that make use of batteries.
digikata 9y ago
I don't think the charging cycles is quite as open and closed as you represent. Its probably 1000 cycles to maintain 80% capacity (or some such threshhold), but you can keep running batteries in a storage-only application them far longer than one would find acceptable for keeping in a car. But overall, yes, there are lot of technical considerations to actually doing it. And the article and discussions just touch the tip of the actual complexity involved - but it seems like there are power arbitrage opportunities of various corners of the grid in both long and short lasting sources.
- tedsanders 9y ago
  I'm not an expert, but my understanding is that reduced capacity of old batteries is a symptom, not the problem. If reduced capacity was the only issue, then yes, it would make total sense to run old batteries into the ground. But the issue is that the reduced capacity is a symptom that the battery is decaying internally, through a variety of mechanisms (cathode/anode micro-cracking, dendrite growth, physical leakage, who knows). Old batteries are dangerous fire risks, exactly what you don't want in a warehouse full of flammable batteries. Even a 1 in 100,000 risk of fire is unacceptably high if it causes a warehouse to explode. For this reason, it's risky to run old batteries into the ground. This is why there isn't a market to turn old electric car batteries into utility-scale storage. Then again, this doesn't seem to be an issue for consumer electronics like laptops and phones and electric toothbrushes, so I wonder what's different, if anything.

mtgx 9y ago

Fortunately for Tesla, it also sells a few more products that make use of batteries.

digikata 9y ago

I don't think the charging cycles is quite as open and closed as you represent. Its probably 1000 cycles to maintain 80% capacity (or some such threshhold), but you can keep running batteries in a storage-only application them far longer than one would find acceptable for keeping in a car. But overall, yes, there are lot of technical considerations to actually doing it. And the article and discussions just touch the tip of the actual complexity involved - but it seems like there are power arbitrage opportunities of various corners of the grid in both long and short lasting sources.

tedsanders 9y ago
I'm not an expert, but my understanding is that reduced capacity of old batteries is a symptom, not the problem. If reduced capacity was the only issue, then yes, it would make total sense to run old batteries into the ground. But the issue is that the reduced capacity is a symptom that the battery is decaying internally, through a variety of mechanisms (cathode/anode micro-cracking, dendrite growth, physical leakage, who knows). Old batteries are dangerous fire risks, exactly what you don't want in a warehouse full of flammable batteries. Even a 1 in 100,000 risk of fire is unacceptably high if it causes a warehouse to explode. For this reason, it's risky to run old batteries into the ground. This is why there isn't a market to turn old electric car batteries into utility-scale storage. Then again, this doesn't seem to be an issue for consumer electronics like laptops and phones and electric toothbrushes, so I wonder what's different, if anything.