djp
Model 3 Performance
To provide some closure to this thread, the ideal setting to extend battery life is to charge to less than 75% SOC.
Why do Li-ion Batteries die? And how to improve the situation?
Why do Li-ion Batteries die? And how to improve the situation?
Here is the response:
"Thanks for this e-mail. I have placed responses within your text using CAPS (not yelling) but so you can find my responses
Jeff Dahn, FRSC
Professor of Physics and Atmospheric Science
NSERC/3M Canada Industrial Research Chair
Canada Research Chair"
"Since electricity appears to have become the defacto currency for renewable energy and I have a great interest in and now investment in renewable technologies (own a Nissan Leaf and Tesla Model S and a 9.8 kW PV system), I have been doing my best to learn whatever I can about energy storage and how batteries work, in particular, the way end user habits effect overall life.
THIS IS AWESOME.
I am wondering if your research has revealed what the best way to extend a batteries life is. I have concluded, as you have noted, that high ambient temperatures degrade these batteries the most. Living in Seattle, we are blessed with a moderate climate so I feel pretty fortunate in that regard.
ABSOLUTELY. AVOID HIGH T WHENEVER POSSIBLE.
Debate continues on whether charging habits will turn out to have much effect on battery life. I have started leaving all of my li-ion consumer products at about 50% charge when they are not in use. Tesla makes this very easy with a battery slider that allows the consumer to choose between 50% and 100% end charging and even has this feature integrated into the phone app to make it very easy to adjust upwards on the fly as long as the car is plugged in. I have installed an 80A (20 kWh) charger so that I can quickly add charge to the Tesla S, allowing me to minimize the inconveniences associated with leaving the pack at a low state of charge and thus increasing the amount of time the battery stays at a mid/low SOC. I tend to do mid pack cycling, discharging generally between 30 and 70% when convenient, while aiming to have the car sit for the longer stretches like overnight, at 50%. I'm not religious about this, just tend to aim in this direction generally.
I THINK THAT IF YOU ARE KEEPING THE CELLS BELOW 4.0V (NO WAY FOR YOU TO TELL THAT, HOWEVER) THE BATTERY LIFE WILL BE VERY IMPRESSIVE. WE ARE TESTING CELLS BUILT IN 2002 THAT HAVE 2002 TECHNOLOGY (LIFETIME IS BETTER NOW) THAT STILL HAVE 75% OF THEIR INITIAL CAPACITY (CYLCED AT 37c THE WHOLE TIME). THESE CELLS WERE CHARGED ONLY TO 4.075V. MODERN CELLS LIKE THOSE IN TESLA CHARGED TO 4.0V SHOULD LAST A FEW DECADES, I SUSPECT, WITHOUT ANY ISSUE (SO KEEP YOUR CAR FROM RUSTING!). WHERE IS 4.0V RELATIVE TO STATE OF CHARGE? MAYBE 75%.
ONE OTHER THING I WOULD RECOMMEND IS TO AVOID HIGH RATE CHARGING AT TEMPERATURE BELOW 0C. ESPECIALLY WHEN THE CELLS ARE ABOVE 75% SOC. TESLA ELECTRONICS MAY PREVENT THIS
In your opinion, do you believe it is worth the effort to keep li-ion batteries at 50% or thereabouts for the bulk of their resting time to extend their long term capacity and if so, do you have any idea how much of a difference this is likely to make over say a 8-15 year time period.
KEEPING BELOW 4.0V MAY DOUBLE OR TRIPLE LIFE TIME COMPARED TO A FULL CHARGE EVERY CYCLE, I SUSPECT.
Also, given that Tesla limits power to the motor during extremes, like high and low charge and high and low temperatures, is there really any reason to avoid running the battery low, assuming Tesla doesn't let you discharge the battery all the way anyway and limits discharge rate as the charge level drops. I assume running the battery to zero (of what the manufacturer allows) does little to the overall life as long as it gets recharged soon after. I assume that low and high states of charge are more an issue if exposure is prolonged, is that correct?
I THINK THAT REALLY DEEP DISCHARGE SHOULD BE AVOIDED AS THEN THE GRAPHITE EMPTIES OF LI AND THE CELL POTENTIAL RISES TO THE POINT WEHRE THE SEI ON THE GRAPHITE SIDE CAN BE DAMAGED. KEEP THE CELLS ABOVE 3.0V PER CELL (NO WAY YOU CAN TELL THAT) BUT THAT WOULD BE ABOUT 98% DISCHARGED. SO DO NOT DISCHARGE BEYOND 98%.
Any opinion you may have on this subject will be much appreciated in helping me understand what the limits of this technology are and how to best treat the batteries in my cars and consumer products.
THE TECHNOLOGY IS REALLY PRETTY AMAZING WHEN YOU THINK OF IT. "
