BEV mass and Regeneration efficiency

[aerohead]

This has been discussed elsewhere but deserves its own thread.
Any advantage or liability attributed to total vehicle mass appears to diverge when comparing ICE and BEV.
A look at the following will tell the tale:
'Comparison between Battery Electric Vehicles and Internal Combustion Engine vehicles fueled by Electrofuels'
Master's Thesis in Sustainable Energy Systems
Tobias Gustafsson & Anders Johansson
Department of Energy and Environment
Chalmers University of Technology
Gothenburg, Sweden, 2015
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The takeaway for me was that, there is a 'sweet spot' for BEV inertia (vehicle mass ), at which an overall optimum efficiency is achieved, with respect to road load and the amount of energy that may be harvested by regeneration.
https://publications.lib.chalmers.se...621/218621.pdf

[redpoint5]

I didn't read it, but what is the theory saying it can be more efficient to have a heavier BEV?

At least with ICE there is a theory that having a denser vehicle can help extend the glide portion of a pulse and glide, and ICE become more efficient with more load.

[aerohead]

Originally Posted by redpoint5

I didn't read it, but what is the theory saying it can be more efficient to have a heavier BEV?

At least with ICE there is a theory that having a denser vehicle can help extend the glide portion of a pulse and glide, and ICE become more efficient with more load.

When every other consideration is made, one will discover that there is an optimum inertia for any particular BEV vehicle, from which its momentum will optimize the amount of regen that can be harvested during deceleration.
Lighter you lose.
Heavier you lose
A 'Goldilocks' mass.

[alexshock]

In theory, relative recuperation efficiency (per 1kg) should be higher for heavier vehicle.
But absolute numbers should be less.

[redpoint5]

Originally Posted by aerohead

When every other consideration is made, one will discover that there is an optimum inertia for any particular BEV vehicle, from which its momentum will optimize the amount of regen that can be harvested during deceleration.
Lighter you lose.
Heavier you lose
A 'Goldilocks' mass.

Still not getting it. It takes x amount of energy to accelerate y mass to z speed. Recovering that momentum is less than 100% efficient, meaning it would always be more efficient to reduce the amount of mass accelerated in the first place.

[oil pan 4]

I do stuff like haul bags of coal, wood pellets with my leaf. Heavier does not appear to be more efficient at all.

[aerohead]

Originally Posted by alexshock

In theory, relative recuperation efficiency (per 1kg) should be higher for heavier vehicle.
But absolute numbers should be less.

Yes, regen efficiency must be balanced against all competing criteria in the mix.

[aerohead]

Originally Posted by redpoint5

Still not getting it. It takes x amount of energy to accelerate y mass to z speed. Recovering that momentum is less than 100% efficient, meaning it would always be more efficient to reduce the amount of mass accelerated in the first place.

'Always' violates the specific attributes possessed by BEVs.
80% of 'braking' kinetic energy can be recovered into the battery of a BEV.
Zero braking energy of an ICE vehicle can be recovered into its fuel tank.
Also, the BSFC-e of a BEV is around 3.5 X lower than an ICE, so they're only using a fraction of the energy to accelerate a vehicle back up to speed.
The mathematics is significantly different.

[aerohead]

Originally Posted by oil pan 4

I do stuff like haul bags of coal, wood pellets with my leaf. Heavier does not appear to be more efficient at all.

There's no implication that it wouldn't.
Volvo is the only company to test and report. And all data reflect only 'passenger car' applications, not towing.
If you were hauling, loaded, between Cloudcroft and Hope, that would be interesting data, compared to dead-heading empty, uphill.

[redpoint5]

Originally Posted by aerohead

'Always' violates the specific attributes possessed by BEVs.
80% of 'braking' kinetic energy can be recovered into the battery of a BEV.
Zero braking energy of an ICE vehicle can be recovered into its fuel tank.
Also, the BSFC-e of a BEV is around 3.5 X lower than an ICE, so they're only using a fraction of the energy to accelerate a vehicle back up to speed.
The mathematics is significantly different.

Some fraction of x is always less than x, even if that fraction is very high. It would always be more efficient to avoid spending energy than attempting to recover it.