4 ms·

Batteries are heavy, and even the weight for a modest sized (15-20kWh) one used for a PHEV is heavy enough (+500-700lbs) to impact the fuel economy enough where

Batteries are heavy, and even the weight for a modest sized (15-20kWh) one used for a PHEV is heavy enough (+500-700lbs) to impact the fuel economy enough where it is a net negative even accounting for regular hybrid recharging/regen braking. You're better off with a significantly smaller regular hybrid battery (1-2kWh) or none at all instead of lugging around the weight of a discharged PHEV battery that'll never reasonably be close to charged from regular driving (unless your regular driving includes ~200 miles only steep downhill braking to fully charge the PHEV battery).

greesil 3y ago
But wouldn't aggressive regenerative braking negate the weight penalty? The hybrid Toyotas I've driven are pretty weak here, but the Chevy Bolt I drove had very strong regenerative braking. As for cost, well, that's what the subsidies are for.
- kenhwang 3y ago
  A Prius Prime has a 161HP/120kW electric motor and a 13.6kWh battery. Regen braking is usually able to capture 15-30% of the motor's output power. You'd have to be at full regen for about 22 minutes to fully charge that battery. That's not a realistic driving pattern for a significantly large majority of people.
omgwtfbyobbq 3y ago
PHEV batteries aren't that heavy these days. The Prius Prime has ~14kWh battery and weights ~290lbs. https://www.sae.org/news/2023/04/2023-toyota-prius-prime-drive https://www.sae.org/news/2023/04/2023-toyota-prius-prime-dri... Even with an extra 200+lbs, having a bigger battery is better for Regen and offsets the additional weight to some extent. If someone is a super conservative/disciplined driver, they can get the same mpg from a hybrid with a smaller pack, but most people don't want to hypermile their cars.
- jacquesm 3y ago
  That is a lot of weight to add to a vehicle, don't forget that every time you accelerate you need to accelerate that weight too.
  - adgjlsfhk1 3y ago
    sure, but 90% of a car's energy goes towards fighting air resistance which doesn't change at all. (and ~20% of the ~10% energy penalty for accelerating gets returned when you brake)
    - gnicholas 3y ago
      Is this true? I recall reading that a large portion (75%?) is due to air resistance at highway speeds, but this is obviously much much lower at low speeds. I would be surprised if driving around town (which is where PHEVs are probably used a good deal, and where there's lots of stop-and-go) resulted in 90% of the energy going to fighting air resistance.
      - jacquesm 3y ago
        Exactly. For highway driving mass isn't all that relevant (it is to road and tire wear, but not for acceleration, after all you really only accelerate once). But in city driving mass is very important and air resistance is hardly a factor.
- kenhwang 3y ago
  Though the Prime is 460lbs heavier than a regular Prius. https://www.motortrend.com/reviews/2023-toyota-prius-prime-first-test-review/ https://www.motortrend.com/reviews/2023-toyota-prius-prime-f... You still need other additional equipment to use the bigger battery. Electric motors aren't light either. Having bigger motors without power to use them is also a waste.
  - omgwtfbyobbq 3y ago
    It is, but it's offset by better efficiency with all other things being equal. The current Prius Prime compared to the Prius is interesting because Toyota traded performance for fuel efficiency with the plug-in. In the last 2 generations of Prius, Toyota kept performance similar and the fuel efficiency of the plug-ins was better than the hybrids. https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=32484&id=31767&id=37163&id=38531 https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=32484&... At this point, having a larger battery/etc should allow better fuel effective even with more weight assuming the same vehicle, performance, etc...

greesil 3y ago

But wouldn't aggressive regenerative braking negate the weight penalty? The hybrid Toyotas I've driven are pretty weak here, but the Chevy Bolt I drove had very strong regenerative braking. As for cost, well, that's what the subsidies are for.

kenhwang 3y ago
A Prius Prime has a 161HP/120kW electric motor and a 13.6kWh battery. Regen braking is usually able to capture 15-30% of the motor's output power. You'd have to be at full regen for about 22 minutes to fully charge that battery. That's not a realistic driving pattern for a significantly large majority of people.

omgwtfbyobbq 3y ago

PHEV batteries aren't that heavy these days. The Prius Prime has ~14kWh battery and weights ~290lbs. https://www.sae.org/news/2023/04/2023-toyota-prius-prime-drive https://www.sae.org/news/2023/04/2023-toyota-prius-prime-dri... Even with an extra 200+lbs, having a bigger battery is better for Regen and offsets the additional weight to some extent. If someone is a super conservative/disciplined driver, they can get the same mpg from a hybrid with a smaller pack, but most people don't want to hypermile their cars.

jacquesm 3y ago
That is a lot of weight to add to a vehicle, don't forget that every time you accelerate you need to accelerate that weight too.
- adgjlsfhk1 3y ago
  sure, but 90% of a car's energy goes towards fighting air resistance which doesn't change at all. (and ~20% of the ~10% energy penalty for accelerating gets returned when you brake)
  - gnicholas 3y ago
    Is this true? I recall reading that a large portion (75%?) is due to air resistance at highway speeds, but this is obviously much much lower at low speeds. I would be surprised if driving around town (which is where PHEVs are probably used a good deal, and where there's lots of stop-and-go) resulted in 90% of the energy going to fighting air resistance.
    - jacquesm 3y ago
      Exactly. For highway driving mass isn't all that relevant (it is to road and tire wear, but not for acceleration, after all you really only accelerate once). But in city driving mass is very important and air resistance is hardly a factor.
kenhwang 3y ago
Though the Prime is 460lbs heavier than a regular Prius. https://www.motortrend.com/reviews/2023-toyota-prius-prime-first-test-review/ https://www.motortrend.com/reviews/2023-toyota-prius-prime-f... You still need other additional equipment to use the bigger battery. Electric motors aren't light either. Having bigger motors without power to use them is also a waste.
- omgwtfbyobbq 3y ago
  It is, but it's offset by better efficiency with all other things being equal. The current Prius Prime compared to the Prius is interesting because Toyota traded performance for fuel efficiency with the plug-in. In the last 2 generations of Prius, Toyota kept performance similar and the fuel efficiency of the plug-ins was better than the hybrids. https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=32484&id=31767&id=37163&id=38531 https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=32484&... At this point, having a larger battery/etc should allow better fuel effective even with more weight assuming the same vehicle, performance, etc...