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Double the density, triple the price? It is interesting that literally the opposite of solid-state batteries is happening. More cars are being sold with LFP ba

Double the density, triple the price? It is interesting that literally the opposite of solid-state batteries is happening. More cars are being sold with LFP batteries which have lower density but are cheaper and have longer life cycles.

cogman10 3y ago
There's a right mix of density/weight that can push things in favor of solid state. For example, if they need less or no cooling and have LFP like lifecycles, then you could see really interesting things in terms of the range. All the sudden a 50kWh solid state battery might compete in range with a 80kWh LFP due to the massively reduced weight. This all remains to be seen though. CATL I think is one of the only manufactures signalling mass production of solid state batteries but it's sort of a "believe it when I see it" situation. (Ditto with sodium batteries).
throitallaway 3y ago
Also I believe LFP chemistry is friendlier to staying pegged at 100% SoC.
- cogman10 3y ago
  Not really, it just has such a long cycle life that staying at 100% means a lot less. The reason manufactures like you to charge to 100% semi-frequently is because LFPs have a fairly flat voltage curve. There's not a lot of difference in voltage between 20% and 80% which means predicting how full the battery is can be tricky for the charge controller. (nothing worse than seeing your car go from 40% to 17% in a heart beat because the controller was off). Charging the car to 100% is the best way to calibrate the charge controller.
  - nimish 3y ago
    Haven't they switched to coulomb counting? No need to infer state of charge from voltage alone.
    - Kirby64 3y ago
      Coulomb counting has issues with accumulated error in any system. LFPs just make things worse. Consider that if the counting is off by only 0.1%, then if you only use coulomb counting to determine state of charge, you will accumulate a 10% error after only 50 charge and discharge cycles. Voltage based readings to "reset" or calibrate the maximum/minimum set points are extremely important. For LFP batteries, they need to be very close to the 100% state of charge to accurately measure. Regular lithium ion can be measured at much lower states or charge (70-90% usually, to my knowledge).
PaulKeeble 3y ago
BYD is selling a bunch of Sodium Ion batteries in China. They are near half the price per KWh but they are bigger and heavier than lithium Ion and LFP. At that price however the cars get cheaper for the same range but the maximum range comes down a bit. Sodium Ion is going to dominate in home storage batteries in a year or two I suspect and mid and low range EVs.
- megaman821 3y ago
  I have been passively following sodium ion for home and grid. Any reliable data on their lifespan? I thought LFPs still retained an advantage of recharge cycles.
  - PaulKeeble 3y ago
    Longer than LFP, 6000 cycles or so, maybe 20 years. For longevity they are really good.
alwayslikethis 3y ago
LFP has other desirable properties as well, such as higher power density (great for acceleration), requiring no cobalt, and being much safer when punctured (doesn't start a fire).

cogman10 3y ago

There's a right mix of density/weight that can push things in favor of solid state. For example, if they need less or no cooling and have LFP like lifecycles, then you could see really interesting things in terms of the range. All the sudden a 50kWh solid state battery might compete in range with a 80kWh LFP due to the massively reduced weight. This all remains to be seen though. CATL I think is one of the only manufactures signalling mass production of solid state batteries but it's sort of a "believe it when I see it" situation. (Ditto with sodium batteries).

throitallaway 3y ago

Also I believe LFP chemistry is friendlier to staying pegged at 100% SoC.

cogman10 3y ago
Not really, it just has such a long cycle life that staying at 100% means a lot less. The reason manufactures like you to charge to 100% semi-frequently is because LFPs have a fairly flat voltage curve. There's not a lot of difference in voltage between 20% and 80% which means predicting how full the battery is can be tricky for the charge controller. (nothing worse than seeing your car go from 40% to 17% in a heart beat because the controller was off). Charging the car to 100% is the best way to calibrate the charge controller.
- nimish 3y ago
  Haven't they switched to coulomb counting? No need to infer state of charge from voltage alone.
  - Kirby64 3y ago
    Coulomb counting has issues with accumulated error in any system. LFPs just make things worse. Consider that if the counting is off by only 0.1%, then if you only use coulomb counting to determine state of charge, you will accumulate a 10% error after only 50 charge and discharge cycles. Voltage based readings to "reset" or calibrate the maximum/minimum set points are extremely important. For LFP batteries, they need to be very close to the 100% state of charge to accurately measure. Regular lithium ion can be measured at much lower states or charge (70-90% usually, to my knowledge).

PaulKeeble 3y ago

BYD is selling a bunch of Sodium Ion batteries in China. They are near half the price per KWh but they are bigger and heavier than lithium Ion and LFP. At that price however the cars get cheaper for the same range but the maximum range comes down a bit. Sodium Ion is going to dominate in home storage batteries in a year or two I suspect and mid and low range EVs.

megaman821 3y ago
I have been passively following sodium ion for home and grid. Any reliable data on their lifespan? I thought LFPs still retained an advantage of recharge cycles.
- PaulKeeble 3y ago
  Longer than LFP, 6000 cycles or so, maybe 20 years. For longevity they are really good.

alwayslikethis 3y ago

LFP has other desirable properties as well, such as higher power density (great for acceleration), requiring no cobalt, and being much safer when punctured (doesn't start a fire).