I have gotten a great deal of benefit from this forum, but I have become concerned that people are getting unsound advice here about how to take care of your battery. Specifically, there are recommendations of things you can do to increase your range that I think are not actually good for your battery.
Taking care of your battery[1,2] is simple and does not require a Ph.D.. I keep my battery between about 30% and 70% for everyday use and then charge to about 95% before I go on a longer trip. You can charge your battery to 90% everyday if you prefer to do that. It is no big deal. I would recommend avoiding going below 15% or 12% unless you are really in a pinch. That is pretty much it. Charging speed is not too important; Tesla knows what they are doing at superchargers. There is one other small thing. Acceleration comes at a small cost. Accelerate all you want, but realize the it diminishes the longevity of your battery very slightly because you are drawing current from your battery at a very high rate[3].
Things that concern me here include recommendations that people charge to 95% and drain to 5% three times for the purpose of increasing your range. This can make the range you see on your display higher, which is ironic because doing those three cycles definitely decreases the capacity of your battery in kW-h (kilo Watt hours). This is just the way the chemistry and physics of the cells in your battery work. There is no way around it. Your battery has a finite number of cycles. It is a large number, but it is finite. You have just wasted 3 of them for the momentary pleasure of seeing a higher number on your screen. This may be called “touching the shore”, which is not only bad for your cells, but has a theory behind it that is unsound because there is a simple relationship between state of charge and voltage that does not change as cells age. The thing that changes is the number of kW-h of energy that your battery stores.
Additionally, going to a high or low state of charge for the purpose of balancing is, for the most part, unnecessary. Tesla is able to monitor the degree of imbalance among your 96 groups of cells. I think they would let you know if that becomes problematic. They monitor intermediate voltages between groups that we cannot see. If your groups are slightly out of balance, the worst thing you can do is go below 12%, because that exposes your weakest groups to bullying by the stronger groups (I.e., getting current pushed through them that they can’t handle well).
It is pretty simple. Charge above 90% only just before you go on a trip. Endeavor to never go below 12%. Sustained acceleration is not free.
Oh, and here is the most important thing that I almost forgot. Set your range to percent, not to miles or kilometers. That will create a good mindset for paying attention to your batteries very simple needs and avoid range obsession. If you need to know how far you can drive, assume 10% will give you at least 25 miles[4].
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1. Your battery is made of cells. It starts with groups of 46 cells in parallel; which establishes a high current capacity. Your battery, in a model 3, is a string of 96 of these groups. It has a high voltage, basically 96 times 3.7 volts at 50% charge and no load. (Be careful who you take advice from. Tesla techs are not generally Li-ion battery experts.
2. There is a relationship between voltage and percent charge at the cellular level, and therefore at all levels. For example:
4.11 volts is 92%
3.97 volts is 80%
3.69 volts is 50%
3.50 volts is 20%
3.4 volts is 12%
Going below 12% is bad for your cells.
3. For normal highway driving your battery would drain to zero in about 3 hours. That means it is drawing current at a rate called C/3. When you accelerate, Tesla allows you to draw about 5C. That is a high rate of current draw, but it is not a big deal because it is for a very brief time. In general, drawing current from a Li-ion battery at more than 2C tends to reduce the battery's longevity.
4. Range table.
10%. 25 miles
20% 50 miles
30% 75 miles
40% 100 miles
…
80% 200 miles
Or, more optimistically:
10%. 30 miles
20% 60 miles
30% 90 miles
40% 120 miles
…
80% 240 miles
The truth will probably lie somewhere in between depending on local conditions, including wind. I get noticeably more range going south than north on 101.
Taking care of your battery[1,2] is simple and does not require a Ph.D.. I keep my battery between about 30% and 70% for everyday use and then charge to about 95% before I go on a longer trip. You can charge your battery to 90% everyday if you prefer to do that. It is no big deal. I would recommend avoiding going below 15% or 12% unless you are really in a pinch. That is pretty much it. Charging speed is not too important; Tesla knows what they are doing at superchargers. There is one other small thing. Acceleration comes at a small cost. Accelerate all you want, but realize the it diminishes the longevity of your battery very slightly because you are drawing current from your battery at a very high rate[3].
Things that concern me here include recommendations that people charge to 95% and drain to 5% three times for the purpose of increasing your range. This can make the range you see on your display higher, which is ironic because doing those three cycles definitely decreases the capacity of your battery in kW-h (kilo Watt hours). This is just the way the chemistry and physics of the cells in your battery work. There is no way around it. Your battery has a finite number of cycles. It is a large number, but it is finite. You have just wasted 3 of them for the momentary pleasure of seeing a higher number on your screen. This may be called “touching the shore”, which is not only bad for your cells, but has a theory behind it that is unsound because there is a simple relationship between state of charge and voltage that does not change as cells age. The thing that changes is the number of kW-h of energy that your battery stores.
Additionally, going to a high or low state of charge for the purpose of balancing is, for the most part, unnecessary. Tesla is able to monitor the degree of imbalance among your 96 groups of cells. I think they would let you know if that becomes problematic. They monitor intermediate voltages between groups that we cannot see. If your groups are slightly out of balance, the worst thing you can do is go below 12%, because that exposes your weakest groups to bullying by the stronger groups (I.e., getting current pushed through them that they can’t handle well).
It is pretty simple. Charge above 90% only just before you go on a trip. Endeavor to never go below 12%. Sustained acceleration is not free.
Oh, and here is the most important thing that I almost forgot. Set your range to percent, not to miles or kilometers. That will create a good mindset for paying attention to your batteries very simple needs and avoid range obsession. If you need to know how far you can drive, assume 10% will give you at least 25 miles[4].
————
1. Your battery is made of cells. It starts with groups of 46 cells in parallel; which establishes a high current capacity. Your battery, in a model 3, is a string of 96 of these groups. It has a high voltage, basically 96 times 3.7 volts at 50% charge and no load. (Be careful who you take advice from. Tesla techs are not generally Li-ion battery experts.
2. There is a relationship between voltage and percent charge at the cellular level, and therefore at all levels. For example:
4.11 volts is 92%
3.97 volts is 80%
3.69 volts is 50%
3.50 volts is 20%
3.4 volts is 12%
Going below 12% is bad for your cells.
3. For normal highway driving your battery would drain to zero in about 3 hours. That means it is drawing current at a rate called C/3. When you accelerate, Tesla allows you to draw about 5C. That is a high rate of current draw, but it is not a big deal because it is for a very brief time. In general, drawing current from a Li-ion battery at more than 2C tends to reduce the battery's longevity.
4. Range table.
10%. 25 miles
20% 50 miles
30% 75 miles
40% 100 miles
…
80% 200 miles
Or, more optimistically:
10%. 30 miles
20% 60 miles
30% 90 miles
40% 120 miles
…
80% 240 miles
The truth will probably lie somewhere in between depending on local conditions, including wind. I get noticeably more range going south than north on 101.
