[ad#post_ad]One of the problems inherent in electric cars is the fact that their batteries degrade. Lithium-ion cells work best when they are new, but over time their ability to hold a charge continually lessens. GM estimates the Volt battery will degrade by 10 to 30% after 8 years/100,000 miles. The company has worked hard to develop methods keep the cells as healthy as possible, and minimize degradation. These methods include keeping the temperature of cells in the ideal (roughly room temperature) range, and not permitting full charges and depletion.
Nonetheless, loss of function is inevitable, and batteries will eventually need to be replaced.
To maximize the potentiating for used cells, GM apparently has significant internal plans to refurbish used cells, as evidenced by a patent application submitted last year.
In the patent application called METHOD AND APPARATUS FOR REJUVENATION OF DEGRADED POUCH-TYPE LITHIUM ION BATTERY CELLS, the automaker spells out a system that would take used lithium-ion pouch cells and restore their function.
It is explained that at cells age, the electrolyte material in them breaks down and leads to the deposit of lithium salts and other polymeric materials on the surfaces of both the positive and negative electrodes. As well, magnesium may be deposited on the negative electrodes. It is believed that both these deposits as well as breakdown of the electrolyte solution itself causes the cells to lose power over time.
In the invention, old cells would be hooked up to a manifold and a specialized solvent would be pumped in under pressure and then heated for up to one hour. A series of potential solvents or mixtures thereof is given.
This treatment is expected to remove the contaminants from the surface of the electrodes, and allow infusion of fresh electrolyte. It is suggested that such treatment may restore the cells to their original level of function.
Much of the patent describes the various ways the tubing and pumping could be designed to fit variety of cells and work under variety of conditions.
The patent concludes that rejuvenation of cells would be much less expensive than manufacturing new ones. One vision describes vehicle owners waiting at a facility while their car battery is rejuvenated on-site. Another vision describes replacing an owner's battery with a new one, and then rejuvenating the old one for secondary use.
You can read the whole patent here .
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