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I’m not a battery expert but some coworkers from the battery lab at work are, and they say that charging more often is better than doing big cycles. On most che

I’m not a battery expert but some coworkers from the battery lab at work are, and they say that charging more often is better than doing big cycles. On most chemistries. In more concrete terms, it’s better to keep the state of charge between for example 60 to 30% compared to for example 80% to 15%. Big cycles like 100% to 5% are the most damaging over time.

1970-01-01 2y ago
This % all depends on how the battery management system (BMS) was designed to manage the state of charge (SOC). Some BMS may set 100% SOC to 80% capacity to prolong the cell and pack lifetime. Additionally, 0% SOC may be set as high as 20% capacity.
- tooltalk 2y ago
  >> Additionally, 0% SOC may be set as high as 20% capacity. << I think that was the case for GM Bolt years ago, but batteries cost a lot of $$ and you won't see more than 5% reserved for buffer these days -- or 95% usuable capacity. Tesla also had software lock limiting access to extra battery capacity on the Model S -- 70KWh instead of 75KW, or about (7%?). No point in carrying around extra weight that costs $3,000 to unlock, but it probably helped prolong battery life.
izzydata 2y ago
Do you know if it is true that a battery reporting 100% is really only 80% and 0% is really about 20%? I heard that somewhere, but have had trouble confirming it. At least for something like a common smartphone.
- SubiculumCode 2y ago
  Probably depends on the device,but I bet that marketing incentives suggest most won't. I mean do you buy the device that says10 hours battery live or 8 hours battery life?
  - plonk 2y ago
    "The battery is messed up after 2 years" is a complaint I've seen and it was pretty damaging to my buying intentions. Just one data point
- radomir_cernoch 2y ago
  I think it's hard to define "the true 100%". It's always a matter of finding a tradeoff between capacity and lifespan – by defining a voltage range.
  - aidenn0 2y ago
    True 100% seems easy for LiPo; it's the point at which it spontaneously catches fire.
    - layer8 2y ago
      “Spontaneously” seems to imply that it’s not actually a deterministic point.
- speedgoose 2y ago
  It depends on the BMS. Some have big buffers, some don’t. One simple clue is how fast it charges relative to the state of charge. If the battery takes a while to go from 95 to 100%, it more likely goes to a full state of charge. If the battery charges very fast to 100%, it probably has some buffer. In my experience, vacuum cleaners and smartphones are designed to destroy the battery as fast as possible, while most car manufacturers will have a big buffer and lie about the true 100%. With some notable exceptions though, like Tesla that allows to charge to 100% with some scary warnings or Nissan that designed some early Leafs battery pack without longevity in mind.
- deleted 2y ago
  [deleted]
Out_of_Characte 2y ago
That defeats the point of having a big battery. You're sacificing battery life to gain battery longevity
- Veliladon 2y ago
  Yes and no. A battery's capacity isn't the only variable. You also have internal resistance. If you have a worn out to hell battery where there's dendrites on the anode and you've basically electroplated the cathode the internal resistance is going to be much higher. So if you draw the same current on a worn battery and a new battery the voltage drop is going to be way higher on that worn battery. If you're already at a low state of charge and you vdroop your way below 3.2V under the current load that battery is going to cut the current. Most people notice it as an Android phone that randomly reboots at low battery.
  - Out_of_Characte 2y ago
    I've bought a phone with a big battery so I could do exactly what the GP said, always charge between 30-80%. But that means I'm cutting half of the potential energy in the battery. I'm lamenting the fact that we have to do this even though film capacitors can be drained from 100% to 0% without damaging the capacitor or reducing its capacity. This is far closer to how you want an energy storage device to operate. Aside from the fact that film capacitors store about a thousand times less energy by every metric.
Veliladon 2y ago
You need to do two things to keep a battery healthy: Keep it low current to stop the ions crashing into shit and not stuffing more ions than the anode and cathode matrixes can hold. If you charge your phone to 100% using a ~4C 60W fast charger you're going to utterly fucking destroy your battery compared to someone who charges to 80% using a 0.5C wireless charger.

1970-01-01 2y ago

This % all depends on how the battery management system (BMS) was designed to manage the state of charge (SOC). Some BMS may set 100% SOC to 80% capacity to prolong the cell and pack lifetime. Additionally, 0% SOC may be set as high as 20% capacity.

tooltalk 2y ago
>> Additionally, 0% SOC may be set as high as 20% capacity. << I think that was the case for GM Bolt years ago, but batteries cost a lot of $$ and you won't see more than 5% reserved for buffer these days -- or 95% usuable capacity. Tesla also had software lock limiting access to extra battery capacity on the Model S -- 70KWh instead of 75KW, or about (7%?). No point in carrying around extra weight that costs $3,000 to unlock, but it probably helped prolong battery life.

izzydata 2y ago

Do you know if it is true that a battery reporting 100% is really only 80% and 0% is really about 20%? I heard that somewhere, but have had trouble confirming it. At least for something like a common smartphone.

SubiculumCode 2y ago
Probably depends on the device,but I bet that marketing incentives suggest most won't. I mean do you buy the device that says10 hours battery live or 8 hours battery life?
- plonk 2y ago
  "The battery is messed up after 2 years" is a complaint I've seen and it was pretty damaging to my buying intentions. Just one data point
radomir_cernoch 2y ago
I think it's hard to define "the true 100%". It's always a matter of finding a tradeoff between capacity and lifespan – by defining a voltage range.
- aidenn0 2y ago
  True 100% seems easy for LiPo; it's the point at which it spontaneously catches fire.
  - layer8 2y ago
    “Spontaneously” seems to imply that it’s not actually a deterministic point.
speedgoose 2y ago
It depends on the BMS. Some have big buffers, some don’t. One simple clue is how fast it charges relative to the state of charge. If the battery takes a while to go from 95 to 100%, it more likely goes to a full state of charge. If the battery charges very fast to 100%, it probably has some buffer. In my experience, vacuum cleaners and smartphones are designed to destroy the battery as fast as possible, while most car manufacturers will have a big buffer and lie about the true 100%. With some notable exceptions though, like Tesla that allows to charge to 100% with some scary warnings or Nissan that designed some early Leafs battery pack without longevity in mind.
deleted 2y ago
[deleted]

Out_of_Characte 2y ago

That defeats the point of having a big battery. You're sacificing battery life to gain battery longevity

Veliladon 2y ago
Yes and no. A battery's capacity isn't the only variable. You also have internal resistance. If you have a worn out to hell battery where there's dendrites on the anode and you've basically electroplated the cathode the internal resistance is going to be much higher. So if you draw the same current on a worn battery and a new battery the voltage drop is going to be way higher on that worn battery. If you're already at a low state of charge and you vdroop your way below 3.2V under the current load that battery is going to cut the current. Most people notice it as an Android phone that randomly reboots at low battery.
- Out_of_Characte 2y ago
  I've bought a phone with a big battery so I could do exactly what the GP said, always charge between 30-80%. But that means I'm cutting half of the potential energy in the battery. I'm lamenting the fact that we have to do this even though film capacitors can be drained from 100% to 0% without damaging the capacitor or reducing its capacity. This is far closer to how you want an energy storage device to operate. Aside from the fact that film capacitors store about a thousand times less energy by every metric.

Veliladon 2y ago

You need to do two things to keep a battery healthy: Keep it low current to stop the ions crashing into shit and not stuffing more ions than the anode and cathode matrixes can hold. If you charge your phone to 100% using a ~4C 60W fast charger you're going to utterly fucking destroy your battery compared to someone who charges to 80% using a 0.5C wireless charger.