4 ms·

LiFePO₄ is also useful for replacing alkaline batteries in small devices, because the cell voltage (3.2V) is approximately 1.5V x 2.

by p1mrx 7y ago

Gibbon1 7y ago
Other advantage is LiFePO4 is a lot safer than cobalt based batteries. My company abandoned cobalt lithium ion batteries in our products because installers will mount our product in utility closets and then people will do things like store cardboard boxes in there.
- mitjak 7y ago
  cardboard boxes. in closets?!?!
  - maxerickson 7y ago
    They mean that the space should be set aside for the equipment, not used for the equipment and also storage.
    - zdragnar 7y ago
      Given the opening reference to safety, I'd assumed the problem work cardboard boxes was fire risk.
      - maxerickson 7y ago
        Sure. You dedicate the space to the equipment for safety reasons.
    - Gibbon1 7y ago
      In commercial you can sort of trust they won't do that. Or it's on them if they do. But with residential properties yeah no. You go look and there is a closet with a water heater and they've got boxes and cleaning supplies stored in there.
baybal2 7y ago
Add to that, in real world conditions very few battery packs can reach 160-170Wh/kg (and hold it after years of use,) while 140Wh/kg LFP been a reality for the last 5 years. They can be more fully charged and discharged, while other lithium cells have to overprovision massively to extend the battery life. This alone makes it so that energy density advantage of NCA cells is thrown out of the window if you count the effective battery pack capacity with BMS sparing cell life. And in comparison to NCA cells, LFPs are much, much cheaper, exactly because of the aforementioned cobalt and nickel use. Phosphates are, after all, spent by tonnes as a fertiliser. Add to that that have a very, very rare trait among chemical batteries — they are stable at high temperatures. This allows for making them work in very hot climates without liquid cooling which would've added a lot to cost and weight. It also allows them to take more regen current, and therefore they don't suffer from as big range reduction from "regen choke" in hot climates. From the above, we also get their higher charge current tolerance, meaning that they can be charged faster. Another very useful trait is their resistance to swell, offgassing and high dimensional stability. This allows for bigger, higher volume fill ratio cells, reducing the battery pack size, and thus its housing mass. Near all "brick" cells are LFP for this exact reason. They age more evenly, unlike other chemistries, and that too contributes to ease of making bigger cells, and lessen the need for battery balancing, reducing charging times. EV makers are stuck with small 18650s because it is very hard to increase cell sizes without not worrying about swelling. And the lower volume to area ratio of 18650s also lead to noticeable mass disadvantage.
- cagenut 7y ago
  > it is very hard to increase cell sizes without not worrying about swelling thank you. i've always wondered why they aren't just the size of like a soda can, or a thermos.
  - robocat 7y ago
    Although 26650 (26mm diameter x 650mm length) Li-Ion are reasonably common.
- kenhwang 7y ago
  Just curious, who else besides Tesla is using 18650s? Or even NCA?
StavrosK 7y ago
What does the voltage depend on? It's interesting and odd to me that it'd be an inherent property of the chemistry.
- detaro 7y ago
  It is an inherent property of the chemistry. It's a property of the electrode materials and how they release/accept electrons during oxidation/reduction (with voltage being a measure of the energy transferred per electron). Keyword is "Standard electrode potential".
  - StavrosK 7y ago
    I'll read up on it, thanks. I'd expect that it was a function of the electrode area or another physical property, so this interests me, thanks again.
eyegor 7y ago
Off topic, but how did you write a subscript character? The hn format page doesn't allude to any markdown/html/rtf support.
- detaro 7y ago
  https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts https://en.wikipedia.org/wiki/Unicode_subscripts_and_supersc...
- MontyCarloHall 7y ago
  By using the Unicode "subscript four" character (https://www.compart.com/en/unicode/U+2084 https://www.compart.com/en/unicode/U+2084) ₀₁₂₃₄₅₆₇₈₉
  - p1mrx 7y ago
    Yeah, I just googled "subscript four" and copied from the first result. There's probably a correct way to do it.
    - TJSomething 7y ago
      The method I've come up with is to install an IME (fcitx) that has a addon that can search the Unicode database for a character. So, I press a key combo, type "subscript four", and press enter.

LiFePO₄ is also useful for replacing alkaline batteries in small devices, because the cell voltage (3.2V) is approximately 1.5V x 2.

by p1mrx 7y ago

LiFePO₄ is also useful for replacing alkaline batteries in small devices, because the cell voltage (3.2V) is approximately 1.5V x 2.

Gibbon1 7y ago

Other advantage is LiFePO4 is a lot safer than cobalt based batteries. My company abandoned cobalt lithium ion batteries in our products because installers will mount our product in utility closets and then people will do things like store cardboard boxes in there.

mitjak 7y ago
cardboard boxes. in closets?!?!
- maxerickson 7y ago
  They mean that the space should be set aside for the equipment, not used for the equipment and also storage.
  - zdragnar 7y ago
    Given the opening reference to safety, I'd assumed the problem work cardboard boxes was fire risk.
    - maxerickson 7y ago
      Sure. You dedicate the space to the equipment for safety reasons.
  - Gibbon1 7y ago
    In commercial you can sort of trust they won't do that. Or it's on them if they do. But with residential properties yeah no. You go look and there is a closet with a water heater and they've got boxes and cleaning supplies stored in there.

baybal2 7y ago

Add to that, in real world conditions very few battery packs can reach 160-170Wh/kg (and hold it after years of use,) while 140Wh/kg LFP been a reality for the last 5 years. They can be more fully charged and discharged, while other lithium cells have to overprovision massively to extend the battery life. This alone makes it so that energy density advantage of NCA cells is thrown out of the window if you count the effective battery pack capacity with BMS sparing cell life. And in comparison to NCA cells, LFPs are much, much cheaper, exactly because of the aforementioned cobalt and nickel use. Phosphates are, after all, spent by tonnes as a fertiliser. Add to that that have a very, very rare trait among chemical batteries — they are stable at high temperatures. This allows for making them work in very hot climates without liquid cooling which would've added a lot to cost and weight. It also allows them to take more regen current, and therefore they don't suffer from as big range reduction from "regen choke" in hot climates. From the above, we also get their higher charge current tolerance, meaning that they can be charged faster. Another very useful trait is their resistance to swell, offgassing and high dimensional stability. This allows for bigger, higher volume fill ratio cells, reducing the battery pack size, and thus its housing mass. Near all "brick" cells are LFP for this exact reason. They age more evenly, unlike other chemistries, and that too contributes to ease of making bigger cells, and lessen the need for battery balancing, reducing charging times. EV makers are stuck with small 18650s because it is very hard to increase cell sizes without not worrying about swelling. And the lower volume to area ratio of 18650s also lead to noticeable mass disadvantage.

cagenut 7y ago
> it is very hard to increase cell sizes without not worrying about swelling thank you. i've always wondered why they aren't just the size of like a soda can, or a thermos.
- robocat 7y ago
  Although 26650 (26mm diameter x 650mm length) Li-Ion are reasonably common.
kenhwang 7y ago
Just curious, who else besides Tesla is using 18650s? Or even NCA?

StavrosK 7y ago

What does the voltage depend on? It's interesting and odd to me that it'd be an inherent property of the chemistry.

detaro 7y ago
It is an inherent property of the chemistry. It's a property of the electrode materials and how they release/accept electrons during oxidation/reduction (with voltage being a measure of the energy transferred per electron). Keyword is "Standard electrode potential".
- StavrosK 7y ago
  I'll read up on it, thanks. I'd expect that it was a function of the electrode area or another physical property, so this interests me, thanks again.

eyegor 7y ago

Off topic, but how did you write a subscript character? The hn format page doesn't allude to any markdown/html/rtf support.

detaro 7y ago
https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts https://en.wikipedia.org/wiki/Unicode_subscripts_and_supersc...
MontyCarloHall 7y ago
By using the Unicode "subscript four" character (https://www.compart.com/en/unicode/U+2084 https://www.compart.com/en/unicode/U+2084) ₀₁₂₃₄₅₆₇₈₉
- p1mrx 7y ago
  Yeah, I just googled "subscript four" and copied from the first result. There's probably a correct way to do it.
  - TJSomething 7y ago
    The method I've come up with is to install an IME (fcitx) that has a addon that can search the Unicode database for a character. So, I press a key combo, type "subscript four", and press enter.