3 ms·

nickel metal hydride? is that really better. i never had good experience with those. lifepo4 is where it's at.

aetherspawn 4y ago
NiMH is "better" for residential (in my opinion) in the sense that it is more inert than any Li-based battery. If you crush or set fire to LiFePo4, it will burn. What's interesting is because Toyota has been developing the NiMH for so long, it has achieved densities of approx. 150Wh/kg, which actually makes it about as good as Lithium technology from 5 years ago, but without any of the stability problems.
- pengaru 4y ago
  NiMH were incredibly annoying back when I last messed with RC cars, which was when NiMH was the latest and greatest battery chemistry in use there. They rarely delivered in practice what was in writing quite promising capacities, and they were incredibly delicate when it came to heat. The wikipedia page for NiMH also mentions things like venting hydrogen gas when overcharged... Looking through the LiFePo4 pages on wikipedia the safety and durability profile seems superior to NiMH, but maybe the LiFePo4 pages there are just fixated on vs. other Li-Ion chemistries. My impression ATM is if you've got LiFePo4 available it's preferable to NiMH. And my personal experience with a LiFePo4 portable battery booster for jumping cars and emergency charging stuff has been an incredibly positive one. The thing is like a tiny weightless magic box that tolerates incredible abuse without losing any charge even stored for a year in desert temps, and somehow manages to put out enough current to start large-displacement high-compression V8s.
- vwoolf 4y ago
  What's interesting is because Toyota has been developing the NiMH for so long, it has achieved densities of approx. 150Wh/kg This is an interesting point; why hasn't Toyota made longer-range plugin hybrids with these batteries, which would seem to be sensical? Looks like the largest battery in a plug-in Prius so far is just 8.8 kWh, according to Wikipedia.
  - aetherspawn 4y ago
    I would guess that there is not much room for them to develop the battery technology further, as it seems they are close to the absolute limit of the materials' performance. So to start a plug-in hybrid program using that battery technology, could be very bad (outpriced, outperformed) if there was suddenly a huge leap forward in Li density and safety.
  - wumpus 4y ago
    > why hasn't Toyota made longer-range plugin hybrids with these batteries Because even Toyota found the Lithium works better for that application.
jazzyjackson 4y ago
NiMH's faults can be compensated for by managing recharge and discharge cycles - toyota has specialized in this for a long time, it's a few steps above your average AA battery
- coryrc 4y ago
  They just only use 40-80% SoC; it's nothing special to carry 2x+ the battery to try and make up for an inferior chemistry. That also doesn't compensate for the high self-discharge rate.

NiMH is "better" for residential (in my opinion) in the sense that it is more inert than any Li-based battery. If you crush or set fire to LiFePo4, it will burn. What's interesting is because Toyota has been developing the NiMH for so long, it has achieved densities of approx. 150Wh/kg, which actually makes it about as good as Lithium technology from 5 years ago, but without any of the stability problems.

pengaru 4y ago
NiMH were incredibly annoying back when I last messed with RC cars, which was when NiMH was the latest and greatest battery chemistry in use there. They rarely delivered in practice what was in writing quite promising capacities, and they were incredibly delicate when it came to heat. The wikipedia page for NiMH also mentions things like venting hydrogen gas when overcharged... Looking through the LiFePo4 pages on wikipedia the safety and durability profile seems superior to NiMH, but maybe the LiFePo4 pages there are just fixated on vs. other Li-Ion chemistries. My impression ATM is if you've got LiFePo4 available it's preferable to NiMH. And my personal experience with a LiFePo4 portable battery booster for jumping cars and emergency charging stuff has been an incredibly positive one. The thing is like a tiny weightless magic box that tolerates incredible abuse without losing any charge even stored for a year in desert temps, and somehow manages to put out enough current to start large-displacement high-compression V8s.
vwoolf 4y ago
What's interesting is because Toyota has been developing the NiMH for so long, it has achieved densities of approx. 150Wh/kg This is an interesting point; why hasn't Toyota made longer-range plugin hybrids with these batteries, which would seem to be sensical? Looks like the largest battery in a plug-in Prius so far is just 8.8 kWh, according to Wikipedia.
- aetherspawn 4y ago
  I would guess that there is not much room for them to develop the battery technology further, as it seems they are close to the absolute limit of the materials' performance. So to start a plug-in hybrid program using that battery technology, could be very bad (outpriced, outperformed) if there was suddenly a huge leap forward in Li density and safety.
- wumpus 4y ago
  > why hasn't Toyota made longer-range plugin hybrids with these batteries Because even Toyota found the Lithium works better for that application.

jazzyjackson 4y ago

NiMH's faults can be compensated for by managing recharge and discharge cycles - toyota has specialized in this for a long time, it's a few steps above your average AA battery

coryrc 4y ago
They just only use 40-80% SoC; it's nothing special to carry 2x+ the battery to try and make up for an inferior chemistry. That also doesn't compensate for the high self-discharge rate.