I have a 60kWh battery and commute 75 miles round trip daily. There is a new Clipper Creek, 16 amp/10 MPH charger at work and I have been using it. With my range, I could charge every other day, but all charging would be at home, or I can charge every day, either at home or the charger or I can charge at home and "top off" daily at the freeby charger. Would the twice a day charging hurt (or help) the battery? (I don't do full charges.)
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EV-lutioin
Active Member
Actually it's "A connected Model S is a happy Model S", but yours means the same thing.
Plug in at home if you can, even if it's just 120V and isn't charging.
Plug in at home if you can, even if it's just 120V and isn't charging.
hybridbear
Active Member
You're best keeping the average SOC as low as possible over time to slow down the calendar degradation. Twice daily charging to a lower charge limit will accomplish this. If the SOC gets too low the voltage gets too low & voltage variation increases which stresses the battery, so try not to get too low. Tests of early Prius hybrids have found that their HVBs have basically no capacity loss because they're only cycled between about 40 & 60% SOC. Battery University says 3.92 V is the idea voltage for charging to maximize life. This approximates to about 60% SOC. If you have a new 60 with a 75 kWh pack, then charging slightly above 60% daily is probably ideal.
Stress hurts lithium ion battery life. Stress occurs at the high end of the battery's charge limit, and at the low end. 60%-40% of charge would definitely keep you in the sweet spot. That being said, the systems that manage these batteries go a long way to manage the amount of stress. Even if you top it off every night, you're likely to only lose a couple of miles of range each year. Enjoy your car and don't stress to much over battery stress.
This isn't a Prius or a Leaf. You don't need to baby the battery. After 4 years and many cars driven 100,000 miles (including Roadsters) there no data to suggest a meaningful impact of SOC on battery life. If 2 or 3 miles of range difference really matters to someone, then they're cutting their trip planning too close.
Just enjoy the car and let the battery management system manage the battery.
NO! What part of keep it plugged in do people not understand?
Doesn't anyone RTFM anymore?
Science fan
Member
Cnasty, I am not an expert on battery life, but I figure I would not charge my S70 the day before, using up some of my usual 185 miles (77%) charge before putting it to bed, plugged in. If the charge fell below 30% while away, then I would use my mobile app to bring it back to 40%. I would use my mobile app to begin charging again to 185 miles a couple of hours before I expect to get home. Other opinions welcome.
How would you do that? The lowest you can set the charge slider is 50%.
If you're really compulsive you could set the charge at 50% before you leave on your trip. If not, just keep it where you usually keep it. It's not like you're going to be away for months. Two weeks is not long term storage.
People are really overthinking this. Just keep the car plugged in and let the battery management system manage the battery.
Science fan
Member
Texas, I was just thinking of doing it manually - charge on, charge off. There is some loss of storage each day that I would keep an eye on and turn on the charge if it got too low; bring it up to 40%. That said, you are probably right. I am overthinking this. Hoping to get ten good years before replacing the battery.
Electric700
Active Member
50 - 60% is ideal for the battery when the car is not going to be used for a few days or more. You can just set the charge level to a value, let's say 55%, and leave the car plugged in. As TexasEV said, the car will handle battery management functions.
Also I think that Tesla designed the battery to last much longer than 10 years. It could go for 20 years or more, so by then you'll probably want the new Tesla Model S 190D
The Tesla battery has a liquid cooling system which is excellent in comparison with the air cooled designs that other cars such as the Nissan Leaf use.
mikeash
Active Member
I plug my car in at every opportunity and always charge to 90%, except for when traveling for a long time (drop to 50% and keep it plugged in) or making long trips (charge to 100% before I go). In the year and five months since I got the car, my 90% rated range has dropped from 239 miles to 236 miles. It has held roughly steady at 236 miles, with some deviations up and down probably due to temperature, for about the past year. From what I've read, this is fairly typical, although not universal. Just plug in and don't worry about it.
hybridbear
Active Member
This paper from NREL has some great info about calendar degradation. Based on this information I will try to keep the SOC of my Model S as low as is practical.
An HVB stored at 80% SOC and around 27 C will only last 10 years. An HVB stored at 60% SOC would have to be around 32 C to only last 10 years. At 27 C it will last much longer. The basic summary: keep the HVB as cool as possible & with the lowest SOC possible (within reason). Calendar degradation is going to be a larger part of total capacity loss than cycling degradation for most EVs. Keeping the HVB SOC as low as possible will add years to the lifetime of the HVB. The battery lifespan is defined as 80% of original capacity. However, don't let the SOC get too low, as this will damage the HVB due to increased stress on each cell as they have to provide the same amount of power with a lower voltage, thus necessitating higher amps (current) which causes more stress due to the internal resistance.
I plan to set my daily charge limit to 60%. If I expect to be driving more than about 75 miles in a day, then I will increase the charge limit so that I don't let the SOC (and thus the cell voltages) get too low. But ideally I will keep my SOC between 40% & 60% most of the time.
By managing the HVB SOC intelligently you can easily add 5+ years to your HVB lifespan. Considering the cost of the HVB, this seems like a smart move to me.
An HVB stored at 80% SOC and around 27 C will only last 10 years. An HVB stored at 60% SOC would have to be around 32 C to only last 10 years. At 27 C it will last much longer. The basic summary: keep the HVB as cool as possible & with the lowest SOC possible (within reason). Calendar degradation is going to be a larger part of total capacity loss than cycling degradation for most EVs. Keeping the HVB SOC as low as possible will add years to the lifetime of the HVB. The battery lifespan is defined as 80% of original capacity. However, don't let the SOC get too low, as this will damage the HVB due to increased stress on each cell as they have to provide the same amount of power with a lower voltage, thus necessitating higher amps (current) which causes more stress due to the internal resistance.
I plan to set my daily charge limit to 60%. If I expect to be driving more than about 75 miles in a day, then I will increase the charge limit so that I don't let the SOC (and thus the cell voltages) get too low. But ideally I will keep my SOC between 40% & 60% most of the time.
By managing the HVB SOC intelligently you can easily add 5+ years to your HVB lifespan. Considering the cost of the HVB, this seems like a smart move to me.
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