SRP Electric

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.

Most auto manufacturers warranty the battery for 8 years and there are even extended warranties available too.

Because the battery pack is under warranty for 8 years you aren’t likely going to be buying a new battery pack any time soon. Let’s pick a number though, say $15,000 to buy a new battery at current prices, and let’s say in the 9th year, you have to replace the battery. We know 3 things about lithium-ion and other evolving batteries types. Eight years down the road they will be;

i) lighter weight,

ii) have much greater power density,

iii) less expensive.

With the way battery technology is evolving, chances are very good that you will be able to get a battery for 1/3 the present cost and quite likely it will provide triple or greater range and your vehicle will be lighter weight, all providing further opportunities for savings.

Battery Acceptance / Receptivity Rates

Note to EV owners and soon-to-be owners:  Your Vehicle Acceptance Rate will determine what type of EV charging station you will choose to install at your home or business.  Depending on your vehicle’s needs, some stations will be ‘overkill’ and make no difference in the time it takes to charge your vehicle (note the yellow highlights in the chart below).  Other charging stations won’t be enough to charge overnight. SRP Electric will be pleased to assist you in this regard!

Battery Acceptance Examples

A)    A Toyota Rav4 EV charging with an LCS-25 charging station with 240V:
Check the Vehicle Acceptance Rate versus the Charging Station Delivery Rate for the LCS-25.  Which is lower?  That will be your limiting factor.  Vehicle Acceptance Rate of the Toyota Rav4 EV is 9.6 kW.  The LCS-25 Delivery Rate is 4.8 kW.  Use 4.8 kW because it is the lower of the two numbers (this is the maximum power the charging station can deliver to the vehicle).
Divide the battery capacity by the lower number from above.  Divide 41.8 kWh by 4.8 kW from above.  The result is 8.71 hours to recharge the battery pack from empty to full.

B)     A Toyota Rav4 EV and a CS-50 charging station with 240V:
Check the Vehicle Acceptance Rate versus the Charging Station Delivery Rate for the CS-50.  Which is lower?  That will be your limiting factor.  Vehicle Acceptance Rate of the Toyota Rav4 is 9.6 kW.  The CS-50 Delivery Rate is 9.6 kW.  Use 9.6 kW because both are the same (it is both the maximum the vehicle will draw and the maximum power the charging station is capable of delivering).
Divide the battery capacity by the lowest number from above.  Divide 41.8 kWh by 9.6 kW from above.  The result is 4.35 hours from empty to full.