New lithium battery charges in one minute
Toshiba has a press release hyping a new lithium battery, which they promise to commercialize in 2006. The big news seems to be the recharging time, which seems nearly physically impossible given that EVs take all night or weekend to charge. But is it?
First of all, the slowness of EV fueling is mostly a myth. Even lead-acid batteries, which are the slowest of all chemistries used, can get topped up to 20% SOC in 5 minutes. The limitations are things like thermal control. That’s pretty fast, though, corresponding to a rate of about 2 C (double the battery’s capacity each hour). This is higher than most lead-acid battery manufacturers recommend, although evidently you can get away with it for awhile if you’re careful. Other fast charge companies are Posicharge (which seems to do 0.6 C) and Minit-Charger, both aimed at the industrial market. A typical manufacturer peak charge rate specification is 0.4 C, which is still enough to get you back on the road after a stop for coffee. Actually achieving these charge rates for a large battery requires a fairly powerful charger, however, which is expensive, so mostly EVs have made do with slower fueling. And finally, to have a truly long and happy life, lead acid batteries like to get fully charged every once in a while, which really does take eight plus hours.
Other chemistries do better. The nickel-cadmium reaction is endothermic, so charging the battery cools it. It can be charged at several C, up to 70% SOC. Nicad charging is more energy efficient when it’s faster, too. (Nicads also like to be fully discharged, making it the most abuse accepting chemistry. Too bad cadmium is so toxic.) NiMH also requires about 1C charging.
Lithium seems to normally be around 1C, though Kokam has some material talking about the behavior of their RC batteries up to 5C. So what rate is this fancy new battery, full of nano-magic? In one minute, it’s supposed to get 80% charged, which corresponds to about 48C. Very fast, about 10x the rate of anything else (except maybe ultracaps), but only 10x faster. So maybe it’s possible. Being able to do it at low cost and with a long lifetime may be the hard part, lots of things work in the lab.