ldallan
Posts: 23
Joined: Mon Jan 16, 2017 10:15 am
Delivery Date: 31 Dec 2016
Leaf Number: 000000

Does very good regen mitigate the extra weight of larger batteries from 40kwh to 100 kwh?

Sun Sep 09, 2018 11:52 am

I have seen a number of posts on how good the regeneration is or isn't on our Leafs, and how it compares to Teslas. My impression is that there isn't enough "hard data" to do much more than speculate.

For our family's "use case", the relatively small 24 kw/hr battery on our 2015 "S" Leaf seems satisfactory. Rather than clamor for more, my inclination is to be ok that I'm not dragging around hundreds of extra pounds of battery for the very few times we drive more than 70 miles in a day.

It may be "confirmation bias" on my part, but I'm underwhelmed by the much larger Bolt and Tesla batteries allowing 200+ miles of range. IIRC, the batteries on the Tesla P65, P80, and P100 weigh from 1000 to 1200+ pounds, compared to the approximately 500 pounds of my 24 kwh Leaf.

But .... it does seem like if an EV has good to very good regeneration, that would significantly compensate for dragging all those extra pounds around.

Regarding range, weight doesn't hurt all that much once you get up to speed, but rather starting and accelerating. But if regeneration is efficient, then the extra weight might not be all that much of a liability.

I've been pondering if a reasonable estimate of regeneration efficiency could be calculated from comparing a hilly route to a flat route. I've read posts about that issue, but they seemed to mostly be guesstimates.

An acquaintance who owns a Tesla claims it has better regeneration compared to the Leaf, perhaps because it has two motors and perhaps less likely to be "maxxed out" when going downhill and/or braking.

cwerdna
Posts: 8090
Joined: Fri Jun 03, 2011 4:31 pm
Delivery Date: 28 Jul 2013
Location: SF Bay Area, CA

Re: Does very good regen mitigate the extra weight of larger batteries from 40kwh to 100 kwh?

Sun Sep 09, 2018 7:01 pm

ldallan wrote:For our family's "use case", the relatively small 24 kw/hr battery on our 2015 "S" Leaf seems satisfactory. Rather than clamor for more, my inclination is to be ok that I'm not dragging around hundreds of extra pounds of battery for the very few times we drive more than 70 miles in a day.

It may be "confirmation bias" on my part, but I'm underwhelmed by the much larger Bolt and Tesla batteries allowing 200+ miles of range. IIRC, the batteries on the Tesla P65, P80, and P100 weigh from 1000 to 1200+ pounds, compared to the approximately 500 pounds of my 24 kwh Leaf.
...

An acquaintance who owns a Tesla claims it has better regeneration compared to the Leaf, perhaps because it has two motors and perhaps less likely to be "maxxed out" when going downhill and/or braking.

First off, battery capacity is measured in kWh. "kw/hr" makes no sense.

Per http://135jik1bbhst1159ri1ax2pj.wpengin ... cation.pdf (from http://www.boronextrication.com/emergen ... rg-hybrid/), 24 kWh Leaf battery pack is 606 lbs.

Not all Teslas have "two motors". Many are RWD. # of motors/drive units has no correlation to regen strength. BMW i3 has a small battery pack but VERY strong regen the moment you let off the accelerator pedal. It can't be dialed back AFAIK (at least not on the early model years). Tesla Roadster was RWD only I hear had very strong regen when letting of the accelerator, as well.

I agree with the bolded part, but unfortunately, that inhibits sub-100 mile range BEVs from being only cars in many households, including mine. And, judging by Tesla's US sales, having 200 to 300+ mile range EVs seems to help with US sales (https://insideevs.com/monthly-plug-in-sales-scorecard/). If I had a BEV that had over 200+ miles of EPA range, I could ditch my "range extender", my 06 Prius.

At my work, we used to have a ton of Leafs. We still have a ton, but many Leafs and other shorter range EVs (e.g. Fiat 500e) have been returned at end of lease and replaced w/longer range ones like Bolts and Model 3's. At the free public L2 charging I sometimes use (has 8 J1772 plugs), I'm sometimes the lone Leaf and sometimes far outnumbered by GM vehicles (Volts and Bolts, mostly) and/or Teslas.

'13 Leaf SV w/premium package (owned)
'13 Leaf SV w/QC + LED & premium packages (lease over, car returned)
'06 Prius

Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

LeftieBiker
Posts: 9219
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 31 May 2013
Location: Upstate New York, US

Re: Does very good regen mitigate the extra weight of larger batteries from 40kwh to 100 kwh?

Sun Sep 09, 2018 9:29 pm

Remember: regeneration doesn't get free power from nowhere. If you live on top of a big hill and get lots of charge added when you leave home, you have to climb that hill to get back, after losing about 60% of the energy you gained when leaving, to heat. Braking in stop and go traffic recovers maybe 40% of the energy normally lost to brake heat, but that just means less waste. And, of course, if you live on flat terrain and make few stops, heavy duty regen will have little effect on your range. The advantage you describe applies best to uses like taxi cab driving.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

SageBrush
Posts: 2680
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: Colorado

Re: Does very good regen mitigate the extra weight of larger batteries from 40kwh to 100 kwh?

Mon Sep 10, 2018 1:53 am

The extra weight mitigation that regen provides is very driver and traffic dependent. At best I'll guess 50% overall in the city; on the highway regen is mostly (hopefully!) not in play and a 250 Kg weight penalty is m*g*f = around 22 Newtons = 10 Wh/mile. This is not a lot and pretty much mirrors people's ICE experience that taking a couple of passengers on a trip does not affect fuel economy in a way most people can notice.

Which is fine as an exercise but you should probably just compare the EPA city and highway test results from fueleconomy.gov:
Tesla Model 3 LR: 300 mile range, 80 kWh battery
City 136 MPGe
Highway 123 MPGe

2017 LEAF
City 124 MPGe
Highway 101 MPGe

Surprised ? Even in the city, the Tesla Model 3 LR has better fuel economy than the 24 kWh LEAF. The take-away lesson here is that overall engineering and car design is more important than the extra weight penalty. Also notice that even in the Model 3 that has an exceptionally low CdA the City MPGe is still higher than Highway, implying that the weight penalty in city driving is less than the Aero losses in highway driving.

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Wh/mile = 33700/MPGe
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
3/2018: 58 Ahr, 28k miles
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2018 Tesla Model 3 LR, Delivered 6/2018

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