Charge loss

[dsm363]

Range charge is a bugger charge so 100% of battery that Tesla gives you access to.

[stopcrazypp]

@jerry33 - I thought that's what you meant.

To make sure my understanding is correct on the other end of the spectrum...

Scenario A
Charge to 80% SOC
Unplug
Wait until 15% SOC
Plug back in

Scenario B
Charge to 70% SOC
Unplug
Wait until 5% SOC
Plug back in

Scenario B is more detrimental to the battery's longevity as well. Correct?

Edit: Removed "range charge" to avoid confusion, hopefully.

AFAIK, the lower end is not detrimental to battery longevity, but it does leave you with very little range left, less battery power (because of lower voltage) and higher risk of under-voltage/bricking. The situation is similar for low temperatures (there is less apparent capacity/power during operation, but no real battery longevity affects).

The reason to minimize the time spent in high SOC is because it promotes oxidation (same with high temperatures), which means quicker degradation of the battery cell. That's why storage mode in the Roadster is 50% SOC.

According to Wikipedia, a laptop cell stored at 100% SOC loses 20% capacity in a year at 25 degrees C. Stored at 40-60%, that reduces five-fold to 4%/year.
Supposedly some chemistries like LiFePO4 are not affected by being stored at high SOC.
Lithium-ion battery - Wikipedia, the free encyclopedia

[StephRob]

I started this thread because someone my husband was talking to said that EVs constantly lose charge and waste electricity. So when they are plugged in they are wasting energy. Sort of like a dripping faucet, or a "vampire" appliance. I realize this is much less important than these issues of battery health and "bricking" and so forth, but I'd love to know the facts on this issue in order to respond to this criticism.

[dsm363]

The car will use a small amount of energy if it's plugged in or not plugged in just with battery management so that amount is the same. The fact that it's plugged in has nothing to do with wasting energy as this guy put it. It uses more energy of course when you start charging. My Roadster might use 1 kWh over a day of just sitting there so about 7 cents worth of electricity. This guy wastes that driving his ICE a few hundred yards.

[StephRob]

My Roadster might use 1 kWh over a day of just sitting there so about 7 cents worth of electricity. This guy wastes that driving his ICE a few hundred yards.

That is very helpful. Thank you!

[stopcrazypp]

I started this thread because someone my husband was talking to said that EVs constantly lose charge and waste electricity. So when they are plugged in they are wasting energy. Sort of like a dripping faucet, or a "vampire" appliance. I realize this is much less important than these issues of battery health and "bricking" and so forth, but I'd love to know the facts on this issue in order to respond to this criticism.

Like dsm636 says, the Model S will draw a small amount of power whether it is plugged in or not (for subsystems, some EVs like the Leaf don't draw any power when "off"). This number is reduced compared to the Roadster. From Tesla's blog, a Model S at 50% SOC would take ~12 months to approach full discharge. 50% of 85kWh = 42.5kWh. Divide this by 365 days and you get 0.116kWh per day on average (or about a 5W draw).

For the Roadster (56kWh), it takes more than 2 months from 50% SOC. 50%*56kWh/60 days = 0.467kWh per day (or about 19.5W draw).

Keep in mind if your ICE car has an alarm system, it also continuously draws power. Given it takes a WHOLE YEAR to drain half a charge, I think it's a non-issue overall.
Plug It In | Blog | Tesla Motors

[dsm363]

That is very helpful. Thank you!

No problem. I don't know the exact amount of energy so that number was a guess. Just from looking at my Roadster, whatever energy usage it is (even sitting in Texas summer outside and unplugged) is so small, I don't even notice it or even think about it when I get back into the car.

Much better analysis from stopcrazypp. I might have even guessed high. Either way, don't think it's really something to worry about.

[jerry33]

@jerry33 - I thought that's what you meant.

To make sure my understanding is correct on the other end of the spectrum...

Scenario A
Charge to 80% SOC
Unplug
Wait until 15% SOC
Plug back in

Scenario B
Charge to 70% SOC
Unplug
Wait until 5% SOC
Plug back in

Scenario B is more detrimental to the battery's longevity as well. Correct?

Depends on if you're driving it or storing it. If you're driving it, both are wrong. If you're storing it the differences between the two methods will be negligible. Charging to over 90% and then letting it sit is harmful.

hcsharp has written the best explanation that I've seen:

From hcsharp: The cathode in Li ion batteries forms defects (microcracks) due to stress caused by expansion and contraction relative to neighboring materials. It is simply bigger or smaller depending on whether it's charged or discharged. The more you discharge it, the more it changes size. And the more it changes size, the more microcracks it gets. These microscopic cracks lower the battery's capacity. That's one reason why smaller cycles, more often, contribute to longer battery life. That's why you should plug it in every night.

Heat aggravates the microcracking process, so keeping your battery cool contributes to longer battery life. And guess what? Your battery heats up more when used at a lower SOC because it requires more amps to keep your car going 65mph than it does at a higher SOC. That's why you should charge it every night.

Capacity fade also comes from the build-up of non-soluble deposits on the anode and cathode. This chemical process happens faster when the battery is warmer. It also happens faster when at a high SOC. But the process slows to a crawl when you drop the SOC to 80 or 90%, and slows only a tiny bit more at 50%. So if you are going to drive your car, keeping it charged in std mode has less impact on battery life (lower amps, less heat) than driving at a lower SOC. But if you're not going to drive your car for a few days, there are no amps or heat to worry about. That's when Tesla recommends putting it in storage mode, which keeps it at a lower SOC.

end of science lesson.

[jerry33]

Note that every modern car uses some power when turned off. In an ICE car, the battery isn't the primary motive source, so the battery doesn't have to be as big. Examples of what ICE cars run when the car is off are:

Security system
Engine fan
Light relay(s) -- In cars that turn the lights off when you open the driver's door a relay keeps the circuit open
Brake pump*
Water pump(s)*
Cabin cooling fan
Telemetry

The only thing an EV adds to the picture is battery thermal management. At the 2 kWh that's been bandied about for extreme temperatures that's 18 cents where I live. 18 cents will go about 4 commuting miles in my 2004 Prius (($0.18/$3.20)*73). Most cars won't go anywhere near that far.

*If these are electrically powered

[gg_got_a_tesla]

I've had an ICE battery die on me when the car was parked for about 3 months without being driven, ostensibly due to the alarm system. If anything, such a scenario would not be an issue with the Model S!