Supercharger effect on battery capacity

Supercharger effect on battery capacity

I've got my eye on an 85kWh Model S, have my test drive next week, am in research mode. Consumer Reports, in their glowing 99-out-of-100 review of the Model S, said, "To charge more than [halfway] at such speed [at a Supercharger] takes longer and would damage the battery." I asked Tesla Motors sales about this, and the rep said basically Superchargers are spaced 150 miles apart so you should never need to charge more than halfway and for the best life of the battery it's best to save Supercharging for road trips and rely on trickle-charging overnight to keep your battery topped up.

Question for Model S owners: Out there in the wild, if you have been relying on Superchargers for your commute or just taking a lot of Tesla-inspired road trips, do you have any anecdotal data to share on any battery capacity losses noted? In our family's case, we anticipate taking maybe five road trips per year--using Superchargers that often shouldn't permanently cut the battery range, right?

Earl and Nagin ... | 3 juillet 2013

I can't be completely sure how Tesla's batteries work since I don't have the proprietary info on their specific characteristics. However, most batteries are harmfully affected by only 3 things: overcharging, deep discharge, and high temperatures.
This means you can charge them at nearly any speed as long as you keep them cool (Tesla's thermal management), don't overcharge them (presumably intelligence in the battery management system), and don't discharge them too low (up to the user).
Presumably, if sensors in the battery detect that the pack is getting too warm, the supercharging will slow down to protect the battery pack.
While I can't be 100% sure Tesla is doing this, they're pretty smart so it is very likely that supercharging won't have any adverse affect on the battery life - ever.

dtesla | 3 juillet 2013

Also an article on "Tips To Keep Your Electric Car’s Battery Healthy In The Record-Breaking Heat Wave" may be helpful.

herkimer | 3 juillet 2013

Elon was asked about this, and said that superchargers would not affect the battery life. As Earl and Nagin noted, Elon also said that what harms the battery most are at the ends of the spectrum: complete discharge, or kept at a full charge and hot. Battery life is best preserved when it is in midrange and cold when not in use.

Superchargers slow considerably as they reach the top of battery capacity. As I understand it, the idea is not to fill completely, except rarely. Possible to fill to 200-240 miles in 20 minutes. The last 10-20% of the battery may take twice as long as the charging slows. I think the idea is that you will rarely need to bring it to the full charge. Topping off at 80 or 90 percent preserves battery best, whichever charging level is used.

If your daily drive is 75 miles, set your charge level to 75 or 80 or 90 percent and don't worry about it until you need to go the full range. If superchargers are 150 miles apart, a 50 mile buffer seems perfectly adequate, and results in quicker charging times as well.

AmpedRealtor | 3 juillet 2013

To be honest, we are overthinking this. The car and battery system were designed to be driven and charged as needed, including high speed supercharging. To think that Tesla designed a car that would be damaged if fully charged at the superchargers is a) completely unproven with no evidence, and b) totally unbelievable.

Enjoy your cars, charge as needed, and don't worry about the rest.

Earl and Nagin ... | 3 juillet 2013

The concern is warranted as Nissan did release their Leaf such that it is damaged by doing things they say you can do to it. The most noticeable example is charging it and leaving it fully charged, in hot weather.
Tesla, however, is not Nissan.
I agree that I don't think there is a problem with the Tesla batteries. We have nearly 60,000 miles on our Roadster that is over 4 years old and we have minimal noticeable range loss. It has driven and charged in temperatures well over 100F many times. It did, however, limit the charging current below the 40 amps available when it needed to, in order to protect the battery.

Brian H | 3 juillet 2013

A field test engineer told me their test cars were filled over and over with a supercharger during trials, and no measurable change occurred. He was awestruck.

portia | 3 juillet 2013

Supercharging to cover your trip and add a little safety margin. This not charging more than half way is nonsense and unwarranted worrying as far as I am aware of. When you go on long trips, use SC as needed, when you are at home (which is probably more often), just charge to the 70% or so that it defaults to, the battery should last a LONG LONG time, (3000 cycles is a LOT of miles!)
I seriously doubt anyone will have data to give you (other than Tesla testing) since it's only been 1 year since the first Model S rolled out the factory.

Brian H | 3 juillet 2013


Earl and Nagin ... | 5 juillet 2013

I'd like to add to portia's comment about charging over 50%. While 50% is optimal, what hurts the battery is having it sit, fully charged for long periods of time (like days or weeks). Filling to 100% and getting on the road within an hour or so doesn't leave it fully charged for very long at all, hence little battery wear.
I would suggest that the amount to charge at Superchargers should be dependent upon how far the next Supercharger is, how much time you want (or don't want) to spend at the current or next Supercharger, and how fast you want to get to your ultimate destination.
Generally, if you want to get to your ultimate destination quickly, you charge only as long as you're charging at max charging speed. When it slows, get on the road again.
The other concern would be if many folks are waiting for a Supercharger, politeness would dictate to get on the road for a fast charge at the next stations instead of continuing to trickle charge at the current one.