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I've always wondered how they do it. They use the same 18650 cells that power laptops, yet laptop batteries degrade badly over time. My 1 year old XPS13 report

I've always wondered how they do it. They use the same 18650 cells that power laptops, yet laptop batteries degrade badly over time. My 1 year old XPS13 reports a battery "wear level" of 29%. I wonder if Tesla's battery technology could be used in laptops and phones?

mschuster91 9y ago
You can replicate it to a certain extent by not discharging below 10-20% (don't know the exact range though). Limiting upper bound is likely either impossible or requires reprogramming the battery control unit. What is also an advantage: Teslas can cool (and I believe also heat) the batteries so they don't enter temperature ranges where degradation is accelerated. In a laptop and certainly a phone there is neither space nor weight available for a thermal management.
- Zekio 9y ago
  Pretty sure all newer thinkpads can be configured to only charge to a threshold
cperciva 9y ago
I wonder if Tesla's battery technology could be used in laptops and phones? Sure, if you want a laptop which you can only recharge once per week. Laptops and phones go through charge cycles much faster than cars; I'm sure Tesla has tuned their designs to maximize performance in that usage environment.
fweespeech 9y ago
It's far less likely real technology and far more likely massively undersold capacity in a Tesla. Laptop and phone batteries are physically close to heat sources + are used frequently to substantial degrees of discharge + frequency of charge cycles after substantial discharge.
rcthompson 9y ago
I think the idea is if you programmed your laptop to never charge the battery past 80% or discharge it past 20%, it would degrade much more slowly, but you would also get about 40% less battery life out of a single "full" charge. Or you would need to increase the battery mass by 66% to get the same battery life. Laptops need to be light enough for a human to carry, while cars don't, and cars are generally expected to last longer than laptops, so the second solution is probably more viable for cars.
- konschubert 9y ago
  My Thinkpad supports limiting the max charge to 80%
leggomylibro 9y ago
I wonder if they're particularly good at balancing the cells. When people recycle 18650s from laptops, I think it's often because one or two cells went bad while the rest remain fairly healthy. Similarly, if you put things like batteries or capacitors in series, you typically want circuitry to balance their voltages, because a pair of 2.7V elements charged to 5.3V could really be at say, 2.75V and 2.55V, which would be unhealthy for the former cell. I think those imbalances are also caused by small differences in the individual elements' properties (capacitors are typically less precisely-tuned than resistors) which will drift further over time with wear and temperature changes and overvoltage conditions and whatnot. So that 2.75V cell would degrade very rapidly compared to the 2.55V one, probably causing even larger imbalances until it eventually fails. Most lithium cells have basic protection circuits built-in against over/under voltage and overcurrent (e.g. shorts,) because they tend to explode if you leave those things out, but they definitely last longer if you pay attention to them as individual cells rather than a system.
- Meegul 9y ago
  A Tesla focused Youtuber recently did a video [1] where he accessed some of the data on the CAN bus, and it showed excellent balancing between the cells. The highest voltage cell reported 3.87V, with the lowest voltage cell reporting 3.864V. So the highest voltage cell has only a 0.1% higher voltage than the lowest. That's in the middle of a discharge cycle, so this may not be representative of the real capacity difference of each cell, but they're being discharging in a very balanced manner. I don't work with batteries often, so take my analysis with a grain of salt, but it seems to me that (the lack of) battery degradation is one of Tesla's biggest strengths when it comes to their battery technology. 1 - https://youtu.be/F3tF0i98MpI https://youtu.be/F3tF0i98MpI
  - jakobegger 9y ago
    Presumably they have a lot of cells in parallel? This would help with balancing, since individual cell differences would average out over all the cells that are parallel.
deleted 9y ago
[deleted]
xenadu02 9y ago
I thought Tesla switched away from the laptop cells some time ago?

mschuster91 9y ago

You can replicate it to a certain extent by not discharging below 10-20% (don't know the exact range though). Limiting upper bound is likely either impossible or requires reprogramming the battery control unit. What is also an advantage: Teslas can cool (and I believe also heat) the batteries so they don't enter temperature ranges where degradation is accelerated. In a laptop and certainly a phone there is neither space nor weight available for a thermal management.

Zekio 9y ago
Pretty sure all newer thinkpads can be configured to only charge to a threshold

cperciva 9y ago

I wonder if Tesla's battery technology could be used in laptops and phones? Sure, if you want a laptop which you can only recharge once per week. Laptops and phones go through charge cycles much faster than cars; I'm sure Tesla has tuned their designs to maximize performance in that usage environment.

fweespeech 9y ago

It's far less likely real technology and far more likely massively undersold capacity in a Tesla. Laptop and phone batteries are physically close to heat sources + are used frequently to substantial degrees of discharge + frequency of charge cycles after substantial discharge.

rcthompson 9y ago

I think the idea is if you programmed your laptop to never charge the battery past 80% or discharge it past 20%, it would degrade much more slowly, but you would also get about 40% less battery life out of a single "full" charge. Or you would need to increase the battery mass by 66% to get the same battery life. Laptops need to be light enough for a human to carry, while cars don't, and cars are generally expected to last longer than laptops, so the second solution is probably more viable for cars.

konschubert 9y ago
My Thinkpad supports limiting the max charge to 80%

leggomylibro 9y ago

I wonder if they're particularly good at balancing the cells. When people recycle 18650s from laptops, I think it's often because one or two cells went bad while the rest remain fairly healthy. Similarly, if you put things like batteries or capacitors in series, you typically want circuitry to balance their voltages, because a pair of 2.7V elements charged to 5.3V could really be at say, 2.75V and 2.55V, which would be unhealthy for the former cell. I think those imbalances are also caused by small differences in the individual elements' properties (capacitors are typically less precisely-tuned than resistors) which will drift further over time with wear and temperature changes and overvoltage conditions and whatnot. So that 2.75V cell would degrade very rapidly compared to the 2.55V one, probably causing even larger imbalances until it eventually fails. Most lithium cells have basic protection circuits built-in against over/under voltage and overcurrent (e.g. shorts,) because they tend to explode if you leave those things out, but they definitely last longer if you pay attention to them as individual cells rather than a system.

Meegul 9y ago
A Tesla focused Youtuber recently did a video [1] where he accessed some of the data on the CAN bus, and it showed excellent balancing between the cells. The highest voltage cell reported 3.87V, with the lowest voltage cell reporting 3.864V. So the highest voltage cell has only a 0.1% higher voltage than the lowest. That's in the middle of a discharge cycle, so this may not be representative of the real capacity difference of each cell, but they're being discharging in a very balanced manner. I don't work with batteries often, so take my analysis with a grain of salt, but it seems to me that (the lack of) battery degradation is one of Tesla's biggest strengths when it comes to their battery technology. 1 - https://youtu.be/F3tF0i98MpI https://youtu.be/F3tF0i98MpI
- jakobegger 9y ago
  Presumably they have a lot of cells in parallel? This would help with balancing, since individual cell differences would average out over all the cells that are parallel.

deleted 9y ago

[deleted]

xenadu02 9y ago

I thought Tesla switched away from the laptop cells some time ago?