I-MMD Clarity versus Accord/Insight Hybrid

[Lowell_Greenberg]

Can anyone compare and contrast at a technical level the the propulsion system differences between the Accord/Insight hybrid and the Clarity Plug-in. They seem to both use i-MMD, except that the Clarity's battery is rechargeable and has a far longer EV range. They both use Atkinson cycle engines, though the Clarity's has a smaller displacement 1.5 liter engine.

There are obvious differences. While the Accord/Insight hybrid is heavily dependent on its ICE, the Clarity is far more dependent on its EV battery SOC for smooth operation. So the balancing act between EV, Hybrid and Engine modes is probably quite different.

Still, the propulsion technology on the Clarity, seems to be one that has evolved over at least two generations, and is therefore more evolutionary than revolutionary. From my vantage point this is a good thing.

It is also interesting that Honda chose to use the Clarity platform and not the Accord or Insight for its current plugin model. I wonder if this was necessitated by the propulsion tech- or a marketing decision to bolster the Clarity concept.

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[Agzand]

Clarity is designed to have a big battery pack below the chassis, Accord/Insight are not. The drive train in Clarity is a cross between Accord (electric motor) and Insight (engine).

Also Clarity uses more lightweight material allowing for the weight of the battery pack and power electronics at reasonable weight. An Accord with similar battery will be a few hundred pounds heavier.

 

[Lowell_Greenberg]

Clarity is designed to have a big battery pack below the chassis, Accord/Insight are not. The drive train in Clarity is a cross between Accord (electric motor) and Insight (engine).

Also Clarity uses more lightweight material allowing for the weight of the battery pack and power electronics at reasonable weight. An Accord with similar battery will be a few hundred pounds heavier.

Also, the Insight and Accord are considered 3rd generation systems- the Clarity is a second generation design.

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[Robert_Alabama]

I've wondered many times why the plug-in version of the Clarity was not built as a Honda Accord PHEV. I guess since Honda had already committed to the Clarity design with the FCV and the BEV, why not go ahead and make the PHEV instead of adapting it to the Accord. Maybe the cost differential was about the same between the two choices, so like you say, choose to strengthen the Clarity line over making both an Accord hybrid and an Accord PHEV. I don't know that anyone other than Honda knows this...

 

[insightman]

I've wondered many times why the plug-in version of the Clarity was not built as a Honda Accord PHEV. I guess since Honda had already committed to the Clarity design with the FCV and the BEV, why not go ahead and make the PHEV instead of adapting it to the Accord. Maybe the cost differential was about the same between the two choices, so like you say, choose to strengthen the Clarity line over making both an Accord hybrid and an Accord PHEV. I don't know that anyone other than Honda knows this...

There's not enough room for the Clarity PHEV's battery in the current Accord platform. Also, the high-strength steels used in the Clarity series help keep the weight of the big battery from collapsing the cabin in a roll-over accident

The Accord Hybrid and the Insight have electric motors that do not rely on rare-earth element magnets. However, I don't believe that necessarily means those motors are more efficient than the Clarity PHEV's rare-earth magnet motors. There's are good reasons why most permanent-magnet vehicle motors are based on those expensive rare-earth elements.

I believe Honda claims the Accord Hybrid and the Insight have slightly more efficient internal combustion engines than the Clarity PHEV.

The biggest difference in the i-MMD operation of the Clarity PHEV vs Honda's small-battery hybrids is the way the Clarity PHEV dispenses with regen braking power when the battery is already fully charged. The non-plug-ins use the regen power coming from the traction motor to drive the starter motor/generator to turn the dormant ICE. The Clarity PHEV does something different that involves running the ICE instead of leaving it dormant.

Interestingly, the Clarity PHEV--the one with the greatest EV range--is the only one of the three that doesn't have an EV Mode button.

 

[Atkinson]

Already stated above, but adding a little color.
Clarity (like the last gen Accord Hybrid) uses second gen i-MMD using higher performance (but less ethically mined) rare earth magnets.
The systems in Accord Hybrid and Clarity PHEV are mostly analogous and comparable within i-MMD generations.
Some of the differences in the Accord i-MMD are realized in higher avg engine MPG (EPA 50 vs 40).
Honda figures you got a Clarity battery worth 50 miles between charges, so they cut back on a few engine features for cost.

 

[insightman]

Honda figures you got a Clarity battery worth 50 miles between charges, so they cut back on a few engine features for cost.

What features did Honda's cost-cutters omit from the Clarity's engine? The 1.5-liter size was selected to maximize efficiency, not to save money. I'll admit there may be other Insight and Accord Hybrid engine features of which I'm not aware.

 

[Atkinson]

I know they pulled the exhaust heated coolant recovery on the Clarity.
Not sure if the Accord has active grill shutters.

BTW, same story with the Malibu Hybrid versus the Volt.
Malibu gets better MPG with a larger engine than the more aerodynamic Volt with a smaller engine for the same reasons.
Battery costs money and engineers didn't want to spend money on an engine that had a shorter duty cycle.

 

[Wdave]

Already stated above, but adding a little color.
Clarity (like the last gen Accord Hybrid) uses second gen i-MMD using higher performance (but less ethically mined) rare earth magnets.
The systems in Accord Hybrid and Clarity PHEV are mostly analogous and comparable within i-MMD generations.
Some of the differences in the Accord i-MMD are realized in higher avg engine MPG (EPA 50 vs 40).
Honda figures you got a Clarity battery worth 50 miles between charges, so they cut back on a few engine features for cost.

To be fair the Clarity weighs almost the same as a Honda Pilot, whereas the Accord hybrid weighs near 700lbs less. All that mass does add up at one point or the other, even at speed on the highway having to keep propelling 4000 pounds of car is going to eat up gas faster than you would expect it.