SRP Electric Blog

Archive for September, 2014

Fast Charging Electric-Car Batteries Could be Less Damaging Than Previously Thought

Posted in: Green on September 24th, 2014

Image: BMW

DC fast charging makes electric cars considerably more practical, allowing drivers to recharge a car’s battery to 80 percent of capacity in half an hour or less.

But quick charging was widely thought to come with a major drawback: While it lowers recharging times, research so far has indicated that fast charging shortens the lifespan of lithium-ion cells.

Now a new study published in the journal Nature Materials (via Green Car Congress) claims quick charging is less damaging than originally thought.

Fast charging itself was found to be less important for battery preservation than the distribution of current through the electrodes.

Led by researchers from Stanford University and the Stanford Institute for Material Sciences (SIMES), the study focused on the behavior of a lithium-iron phosphate cathode material.

Researchers built small coin-cell batteries and charged them with different amounts of current for various periods of time. The batteries were then disassembled and examined with an x-ray to see how they responded.

If a higher percentage of the nanoparticles in a cathode absorb and release ions during charging discharging, it will last longer. If only a smaller proportion are involved, the battery will gradually degrade.

After examining the test batteries, researchers found that only a small amount of nanoparticles were absorbing and releasing ions–whether fast charging or not.

However, they found that the distribution of ions became more uniform above a certain threshold.

The study’s authors say scientists may be able to take advantage of this effect to create longer-lasting batteries.

The next phase of this research will involve cycling batteries through hundreds–or perhaps thousands–of cycles to simulate real-world use.

Researchers also plan to x-ray batteries while they are charging to get a better idea of how the materials behave.

Meanwhile, electric-car owners are likely to continue using the growing number of DC fast-charging stations in the U.S.–but now they may be able to do so more confidently.

Why Electric-Car Charging At Work Matters

Posted in: Green on September 2nd, 2014

For many electric car owners, charging at work is a nice bonus, but not a necessity.

For others, it’s the difference between choosing an electric vehicle, and not doing so–the extra charge at work makes all the difference.

But there’s another reason charging at work is important, and it’s all to do with the electricity grid and the “duck curve”.

Chargepoint founder and CTO CEO Richard Lowenthal explains the duck curve–and the benefits of charging in the “duck’s belly” on Greentech Media.

As we all know, electricity use ebbs and flows.

Households and businesses turn on their lights and computers early in the day, leading to a small energy surge. During the day, use is pretty consistent.

But as the world goes home for the evening, lights, televisions, air conditioners, ovens and other electrical appliances are all used at once, leading to a spike in demand that energy companies must always be prepared for.

Utilities are prepared all day, of course–varying generation according to how much energy is used at peak times.

The trouble is, power stations can’t match output precisely with use–any extra use would catch out the grid and the lights would go out.

Running a power plant at lower loads is often inefficient too–they have to be producing a constant flow of energy to be working efficiently. And ideally, people need to be using this energy.

This is where the “duck curve” comes in.

Developed by the California Independent System Operator, or CAISO, it’s based on the possible future scenario where customer-sited solar panels reduce the demand of grid-sourced electricity to very low levels.

This is most likely on sunny but cool days in the spring and fall, when air conditioner usage is lower than that of mid summer, and households and businesses are drawing less power.

Energy companies would have to reduce generation to avoid producing far more electricity than is used–but still have to crank up the power towards the end of the day when people come home from work and begin using electrical appliances in huge numbers.

This is the “duck’s belly”–a deep curve of reduced generation leading into a steep climb at the end of the day–an inefficient way of generating power.


The duck curve graph shows future energy generation figures as more and more renewable energy is generated during the day–and the disparity between power generation during the day and towards the end of the day grows. The duck’s belly gets deeper.

Workplace charging could fix this scenario, by giving us a flatter duck.

That doesn’t sound great for our aquatic friend, but it’s good for generation.

Should thousands of electric vehicles plug in at work during the day, energy suppliers would need to generate more power during this period.

This reduces the “belly”, in turn reducing the “ramp” towards 8pm, and more consistent generation means greater efficiency.

It costs money to generate power, so generating it more efficiently is much better value for all parties involved–helping reduce costs for the customer.