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+1 for battery university, they're an excellent source. Does anyone have any other suggestions for similarly technically deep (while approachable) articles on a

+1 for battery university, they're an excellent source. Does anyone have any other suggestions for similarly technically deep (while approachable) articles on any other facet consumer electronics? My understanding from this article is that: 1. Charge the battery to as low a max percentage as possible (till about 65%) 2. Keep it as cool as possible (up to zero degrees C at least) 3. Use it as little as possible before recharging it (minimize charge-discharge bandwidth) Aka, over-rate and over size the battery if you're building the device, and minimize extremes on any side of soc (state of charge). Do EV manufacturers use any other tricks not covered by this? (Of course, use the device as needed, these are just guidelines for the best perfomance.)

stavros 9mo ago
I don't think this advice is useful. You're going to use your devices, so you won't control the temperature or, largely, the charge percentage. I think good advice is to keep your devices as cool as you can (ie don't leave your cars in sunlight when there's shade), which you probably did anyway, and keep the battery between 20% and 80% as much as possible. If the battery is going to stay unused for a while, leave it at 3.8V (or close to it), or at 50%. Batteries are ultimately consumables, so don't stress too much. Just care for them as much as convenient, and that's it.
- user_7832 9mo ago
  > You're going to use your devices, so you won't control the temperature or, largely, the charge percentage. > I think good advice is to keep your devices as cool as you can (...), and keep the battery between 20% and 80% as much as possible. Yeah that's kinda what I meant. Where it's easy or possible to do so (for eg lots of modern laptops & phones allow charge limits), it's better to follow these guidelines. > Batteries are ultimately consumables, so don't stress too much. Just care for them as much as convenient, and that's it. Yeah I agree (and that's what I meant by my last sentence), however, a lot of people (including eg my dad!) end up having battery issues while being unaware that they can do things to protect their hardware. For example, my phone has enough capacity to last the whole day even at 60% of it's capacity. I've set it to stop charging at 80% (the lowest possible SOC) for this reason. On my laptop, I frequently reduce it to 60% as I use it plugged in. > I don't think this advice is useful. I'm afraid I don't get what's not helpful? We're probably talking across each other.
  - stavros 9mo ago
    It came across to me as "keep your batteries always under 0 C", which obviously almost nobody can do, and it leads to a sense of "eh, I won't go to these lengths, might as well do nothing", which is counterproductive. I see the same reaction with healthy eating, where people are so put off by extremely militant advice that they think "I can't eat only vegetables all day, fuck it, I'll eat these three cheeseburgers". I agree with your second comment, the first one just could be misconstrued as very hard-to-follow advice.
    - Filligree 9mo ago
      That's backwards. At too low temperatures batteries start to take damage during discharge or (especially) charge, so 0C is the lowest temperature at which you should charge it. 5C would be better. It's a concern mainly for e.g. offgrid batteries being used in the winter.
      - stavros 9mo ago
        I know, but "as cool as possible (up to zero degrees C at least)" is conflicting, and kind of means "below zero degrees".
- VorpalWay 9mo ago
  > I think good advice is to keep your devices as cool as you can (ie don't leave your cars in sunlight when there's shade), In some climates, such as where I live, the larger issue is the cold in the winter. From what I understand, Li-ion batteries don't like being charged below 0 C. And it is not uncommon for it to dip to -15 C or even -20 C here. Really, from what I understand, batteries want to be kept above freezing but cool. So yeah, don't leave it in direct sunlight in the middle of summer. The more difficult problem is the winter (unless you happen to have a heated garage).
  - stavros 9mo ago
    Yeah, they lose capacity temporarily when it's very cold. Most EVs now precondition the battery before charging by heating it up.
SV_BubbleTime 9mo ago
> Do EV manufacturers use any other tricks not covered by this? Automotive EE here. EV aren’t ready for world wide use. That statement is constantly ignored by people in California who see zero issues with their new expensive fancy cars. Shortest version… The heating and cooling systems of the battery are there to prevent damage. BUT… who powers the heating and cooling systems? The battery of course. In a traditional or better yet a plugin hybrid, you can use the gas engine to control how much electric you are using in conditions that would be harmful to the battery. In EV vehicles you have no choice. The car won’t tell you “you can’t drive right now”. The marketing of EVs was a mistake, and every mfg is paying for it. Ford taking a 2 billion write off this year on their EV line and canceling a lot of their vehicles. They will be cool, but this generation makes a great second vehicle or town vehicle. Absolutely not an extreme weather highway vehicle.
- user_7832 9mo ago
  > EV aren’t ready for world wide use. Fully agree (I'm 100% team PHEV or EREV/REEV) as a mechanical engineer. IMO BEVs and PHEVs/REEVs should be on parity in terms of tax/govt incentives, while encouraging electric use - for eg, subsidized (PH)EV charging, high(er) costs in city centres if running in ICE mode, etc. I was just curious if EV manufacturers use any other tricks that're "well known" in EV-land but not for the average consumer.
  - kanbankaren 9mo ago
    AFAIK, they charge only to 4.0 V. I think the batteries on satellites are also charged only to 4.0 V
    - user_7832 9mo ago
      Thanks! That's very helpful (and unsurprising) to know. Any idea if satellites use LTO batteries btw? They have much longer lives and apparently can tolerate much more abuse.
  - simulator5g 9mo ago
    These acronyms are a nightmare, what the hell is a PHEV? EREV? PZEV? Consumers are just expected to know this stuff somehow, it’s nuts. Sometimes I buy parts for my car and just hope I selected the right one, because some models are PZEV/not PZEV but the sticker that would tell me has turned completely white & can’t be read.
HPsquared 9mo ago
Light bulbs (including LEDs) are similar. If you use them at slightly lower then their maximum rating, things tend to last a LOT longer. The "Dubai lamp" uses this concept - oversized LEDs that are derated, and last a very long time (100k hours). You can do the same by buying oversized dimmable LEDs and simply turning down the brightness.
- butvacuum 9mo ago
  That doesn't help nearly as much as reducing the current through them. And, PWM doesn't change the lumens per watt at all.
averynicepen 9mo ago
Degradation is driven by many things, but a big one is heat. Elevated temperatures during both charge and discharge is very bad for battery longevity. To manage this, almost all EVs use liquid cooling, with a cold plate directly contacting as many battery cells as they can to move heat out of the battery. This coolant is then cooled by a radiator, an AC chiller, or both. The worst temperature abuse case is DC fast charging, aka Supercharging, where high current charging creates tons of heat due to resistive losses. This is why frequent fast charging causes faster battery degradation, but ordinary charging and driving does not, because the coolant loop is sized for the DC fast charge heat transfer requirements. Besides removing heat, adding heat into the system is also desirable. Cold weather environments approaching freezing or below is also bad for battery longevity, and more importantly, terrible for range. Resistive heaters are super power hungry, and to heat the battery coolant loop requires power from the battery. This is why, conventionally, EVs are terrible in cold weather. > Do EV manufacturers use any other tricks not covered by this? And now, onto the magic trick. Heat management is so important to both the driving range and the longevity of a vehicle that EVs have moved from traditional resistive heaters to heat pumps. These magical thermodynamic devices can move heat from anywhere, including drawing heat out of cold ambient air. When you combine that with a valve design that allows the heat pump to access the battery coolant loop, the motor drivetrain coolant loop, the cabin coolant loop, the vehicle computer(s) coolant loops, and external ambient temperature, you can have a super efficient system that shuffles heat where it's "wasted" to where it's "needed". Tesla has an excellent video briefly covering their heat pump and their very clever Octovalve design: https://www.youtube.com/watch?v=DyGgrkeds5U https://www.youtube.com/watch?v=DyGgrkeds5U For more depth, this video covers the heat pump and the ~22 different sources of heat it can draw heat from: https://www.youtube.com/watch?v=Dujr3DRkpDU https://www.youtube.com/watch?v=Dujr3DRkpDU

stavros 9mo ago

I don't think this advice is useful. You're going to use your devices, so you won't control the temperature or, largely, the charge percentage. I think good advice is to keep your devices as cool as you can (ie don't leave your cars in sunlight when there's shade), which you probably did anyway, and keep the battery between 20% and 80% as much as possible. If the battery is going to stay unused for a while, leave it at 3.8V (or close to it), or at 50%. Batteries are ultimately consumables, so don't stress too much. Just care for them as much as convenient, and that's it.

user_7832 9mo ago
> You're going to use your devices, so you won't control the temperature or, largely, the charge percentage. > I think good advice is to keep your devices as cool as you can (...), and keep the battery between 20% and 80% as much as possible. Yeah that's kinda what I meant. Where it's easy or possible to do so (for eg lots of modern laptops & phones allow charge limits), it's better to follow these guidelines. > Batteries are ultimately consumables, so don't stress too much. Just care for them as much as convenient, and that's it. Yeah I agree (and that's what I meant by my last sentence), however, a lot of people (including eg my dad!) end up having battery issues while being unaware that they can do things to protect their hardware. For example, my phone has enough capacity to last the whole day even at 60% of it's capacity. I've set it to stop charging at 80% (the lowest possible SOC) for this reason. On my laptop, I frequently reduce it to 60% as I use it plugged in. > I don't think this advice is useful. I'm afraid I don't get what's not helpful? We're probably talking across each other.
- stavros 9mo ago
  It came across to me as "keep your batteries always under 0 C", which obviously almost nobody can do, and it leads to a sense of "eh, I won't go to these lengths, might as well do nothing", which is counterproductive. I see the same reaction with healthy eating, where people are so put off by extremely militant advice that they think "I can't eat only vegetables all day, fuck it, I'll eat these three cheeseburgers". I agree with your second comment, the first one just could be misconstrued as very hard-to-follow advice.
  - Filligree 9mo ago
    That's backwards. At too low temperatures batteries start to take damage during discharge or (especially) charge, so 0C is the lowest temperature at which you should charge it. 5C would be better. It's a concern mainly for e.g. offgrid batteries being used in the winter.
    - stavros 9mo ago
      I know, but "as cool as possible (up to zero degrees C at least)" is conflicting, and kind of means "below zero degrees".
VorpalWay 9mo ago
> I think good advice is to keep your devices as cool as you can (ie don't leave your cars in sunlight when there's shade), In some climates, such as where I live, the larger issue is the cold in the winter. From what I understand, Li-ion batteries don't like being charged below 0 C. And it is not uncommon for it to dip to -15 C or even -20 C here. Really, from what I understand, batteries want to be kept above freezing but cool. So yeah, don't leave it in direct sunlight in the middle of summer. The more difficult problem is the winter (unless you happen to have a heated garage).
- stavros 9mo ago
  Yeah, they lose capacity temporarily when it's very cold. Most EVs now precondition the battery before charging by heating it up.

SV_BubbleTime 9mo ago

> Do EV manufacturers use any other tricks not covered by this? Automotive EE here. EV aren’t ready for world wide use. That statement is constantly ignored by people in California who see zero issues with their new expensive fancy cars. Shortest version… The heating and cooling systems of the battery are there to prevent damage. BUT… who powers the heating and cooling systems? The battery of course. In a traditional or better yet a plugin hybrid, you can use the gas engine to control how much electric you are using in conditions that would be harmful to the battery. In EV vehicles you have no choice. The car won’t tell you “you can’t drive right now”. The marketing of EVs was a mistake, and every mfg is paying for it. Ford taking a 2 billion write off this year on their EV line and canceling a lot of their vehicles. They will be cool, but this generation makes a great second vehicle or town vehicle. Absolutely not an extreme weather highway vehicle.

user_7832 9mo ago
> EV aren’t ready for world wide use. Fully agree (I'm 100% team PHEV or EREV/REEV) as a mechanical engineer. IMO BEVs and PHEVs/REEVs should be on parity in terms of tax/govt incentives, while encouraging electric use - for eg, subsidized (PH)EV charging, high(er) costs in city centres if running in ICE mode, etc. I was just curious if EV manufacturers use any other tricks that're "well known" in EV-land but not for the average consumer.
- kanbankaren 9mo ago
  AFAIK, they charge only to 4.0 V. I think the batteries on satellites are also charged only to 4.0 V
  - user_7832 9mo ago
    Thanks! That's very helpful (and unsurprising) to know. Any idea if satellites use LTO batteries btw? They have much longer lives and apparently can tolerate much more abuse.
- simulator5g 9mo ago
  These acronyms are a nightmare, what the hell is a PHEV? EREV? PZEV? Consumers are just expected to know this stuff somehow, it’s nuts. Sometimes I buy parts for my car and just hope I selected the right one, because some models are PZEV/not PZEV but the sticker that would tell me has turned completely white & can’t be read.

HPsquared 9mo ago

Light bulbs (including LEDs) are similar. If you use them at slightly lower then their maximum rating, things tend to last a LOT longer. The "Dubai lamp" uses this concept - oversized LEDs that are derated, and last a very long time (100k hours). You can do the same by buying oversized dimmable LEDs and simply turning down the brightness.

butvacuum 9mo ago
That doesn't help nearly as much as reducing the current through them. And, PWM doesn't change the lumens per watt at all.

averynicepen 9mo ago

Degradation is driven by many things, but a big one is heat. Elevated temperatures during both charge and discharge is very bad for battery longevity. To manage this, almost all EVs use liquid cooling, with a cold plate directly contacting as many battery cells as they can to move heat out of the battery. This coolant is then cooled by a radiator, an AC chiller, or both. The worst temperature abuse case is DC fast charging, aka Supercharging, where high current charging creates tons of heat due to resistive losses. This is why frequent fast charging causes faster battery degradation, but ordinary charging and driving does not, because the coolant loop is sized for the DC fast charge heat transfer requirements. Besides removing heat, adding heat into the system is also desirable. Cold weather environments approaching freezing or below is also bad for battery longevity, and more importantly, terrible for range. Resistive heaters are super power hungry, and to heat the battery coolant loop requires power from the battery. This is why, conventionally, EVs are terrible in cold weather. > Do EV manufacturers use any other tricks not covered by this? And now, onto the magic trick. Heat management is so important to both the driving range and the longevity of a vehicle that EVs have moved from traditional resistive heaters to heat pumps. These magical thermodynamic devices can move heat from anywhere, including drawing heat out of cold ambient air. When you combine that with a valve design that allows the heat pump to access the battery coolant loop, the motor drivetrain coolant loop, the cabin coolant loop, the vehicle computer(s) coolant loops, and external ambient temperature, you can have a super efficient system that shuffles heat where it's "wasted" to where it's "needed". Tesla has an excellent video briefly covering their heat pump and their very clever Octovalve design: https://www.youtube.com/watch?v=DyGgrkeds5U https://www.youtube.com/watch?v=DyGgrkeds5U For more depth, this video covers the heat pump and the ~22 different sources of heat it can draw heat from: https://www.youtube.com/watch?v=Dujr3DRkpDU https://www.youtube.com/watch?v=Dujr3DRkpDU