ashdeacon
Posts: 12
Joined: Thu Sep 20, 2018 12:05 pm
Delivery Date: 02 Sep 2018
Leaf Number: 307779

Cruising to a stop down hill.

Sat Sep 22, 2018 11:10 am

Hi all,

I have an energy regeneration question for you. I looked around and some similar items have been discussed but not quite the same.

This is a real life example, since I live at the bottom of a long descent....

Say I am driving down a long hill and I need to stop at the bottom of the hill.

I basically have 3 options which all involved energy recapture.

I can gradually regenerate over the whole descent in D mode.

Or I could brake more later in the slope in B mode

Or I could brake really late with the e-pedal.

I guess my question is does gentler more gradually regeneration capture more energy vs more intense energy regen??

I guess the real answer is to do a real life experiment, though I am not sure I have sensitive enough readouts of battery charge to make this meaningful...

Ash.

alozzy
Posts: 1165
Joined: Fri Jan 20, 2017 4:25 pm
Delivery Date: 18 Jan 2017
Location: Vancouver, BC
Contact: Website

Re: Cruising to a stop down hill.

Sat Sep 22, 2018 1:02 pm

I would think the regen rate won't affect efficiency, unless you exceed 30 kW (the max regen rate).

What's more likely to impact overall efficiency is air drag at higher speeds. So, I would likely use ECO level regen down the entire hill as that should keep your speed in check best and thereby lower losses due to air drag.
Vancouver, CA owner of a 2013 Ocean Blue SV + QC, purchased 01/2017 in WA
Zencar 12/20/24/30A L1/L2 portable EVSE
1-1/4" Curt #11396 hitch
After market, DIY LED DRLs
LeafSpy Pro + Konnwei KW902 ELM327 BT OBDII dongle
Loving my first BEV :D

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Nubo
Posts: 4909
Joined: Fri May 28, 2010 11:01 am
Delivery Date: 31 Oct 2014
Location: Vallejo, CA

Re: Cruising to a stop down hill.

Sat Sep 22, 2018 11:39 pm

ashdeacon wrote:Hi all,

I have an energy regeneration question for you. I looked around and some similar items have been discussed but not quite the same.

This is a real life example, since I live at the bottom of a long descent....

Say I am driving down a long hill and I need to stop at the bottom of the hill.

I basically have 3 options which all involved energy recapture.

I can gradually regenerate over the whole descent in D mode.

Or I could brake more later in the slope in B mode

Or I could brake really late with the e-pedal.

I guess my question is does gentler more gradually regeneration capture more energy vs more intense energy regen??

I guess the real answer is to do a real life experiment, though I am not sure I have sensitive enough readouts of battery charge to make this meaningful...

Ash.


The slower descent will give you more charge. Otherwise the vehicle speeds up and encounters more air resistance. Drag increases with the square of the airspeed so doubling speed gives 4 times more drag and the energy will go towards fighting drag instead of charging the battery.
I noticed you're still working with polymers.

ashdeacon
Posts: 12
Joined: Thu Sep 20, 2018 12:05 pm
Delivery Date: 02 Sep 2018
Leaf Number: 307779

Re: Cruising to a stop down hill.

Sun Sep 23, 2018 3:42 pm

Good point on the speed drag.... I will aim for constant smooth speed and gradually braking as I near my end point.

Ash.

LeftieBiker
Posts: 9584
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 31 May 2013
Location: Upstate New York, US

Re: Cruising to a stop down hill.

Sun Sep 23, 2018 4:21 pm

There is another loss during hard regenerative braking: heat. The faster energy gets dumped into the drive, the more waste heat gets produced.
Last edited by LeftieBiker on Sun Sep 23, 2018 9:20 pm, edited 1 time in total.
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.

ashdeacon
Posts: 12
Joined: Thu Sep 20, 2018 12:05 pm
Delivery Date: 02 Sep 2018
Leaf Number: 307779

Re: Cruising to a stop down hill.

Sun Sep 23, 2018 5:44 pm

Yes, so both these factors would argue against going Neutral (accelerating down the hill by gravity) and then braking a lot in B or e-pedal and suggest more gradually D all the way down may be more beneficial.

Ash.

alozzy
Posts: 1165
Joined: Fri Jan 20, 2017 4:25 pm
Delivery Date: 18 Jan 2017
Location: Vancouver, BC
Contact: Website

Re: Cruising to a stop down hill.

Sun Sep 23, 2018 6:12 pm

The correct answer is - it depends...

On less steep grades, you can often coast in neutral the whole time. On steeper grades, I usually use ECO regen and put it into B mode only if I'm still picking up too much speed.

So, there aren't really any golden rules to lean on for all circumstances, it's a bit of an art and there's definitely a learning curve but it's worth the effort on longer trips.
Vancouver, CA owner of a 2013 Ocean Blue SV + QC, purchased 01/2017 in WA
Zencar 12/20/24/30A L1/L2 portable EVSE
1-1/4" Curt #11396 hitch
After market, DIY LED DRLs
LeafSpy Pro + Konnwei KW902 ELM327 BT OBDII dongle
Loving my first BEV :D

ashdeacon
Posts: 12
Joined: Thu Sep 20, 2018 12:05 pm
Delivery Date: 02 Sep 2018
Leaf Number: 307779

Re: Cruising to a stop down hill.

Sun Sep 23, 2018 8:04 pm

Understood.

I never even looked into Eco Mode to be honest. Mainly because I did not like the unresponsive throttle. So I assume Eco regen braking is somewhere between D and B mode?

I will give it a try on my next descent....

Thx
Ash

LeftieBiker
Posts: 9584
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 31 May 2013
Location: Upstate New York, US

Re: Cruising to a stop down hill.

Sun Sep 23, 2018 9:21 pm

Eco mode is especially handy because it provides the right amount of regenerative braking to just maintain speed on most hills.
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.

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Nubo
Posts: 4909
Joined: Fri May 28, 2010 11:01 am
Delivery Date: 31 Oct 2014
Location: Vallejo, CA

Re: Cruising to a stop down hill.

Mon Sep 24, 2018 3:09 am

ashdeacon wrote:Understood.

I never even looked into Eco Mode to be honest. Mainly because I did not like the unresponsive throttle. So I assume Eco regen braking is somewhere between D and B mode?

I will give it a try on my next descent....

Thx
Ash


Eco mode only re-maps the throttle curve, it does not remove any level of performance. I.e., you still have have command of the full 0-100% of power. I find it extremely helpful for smooth driving at lower speeds as it takes away the twitchiness, and if I want high power it's still there.
I noticed you're still working with polymers.

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