Regen question

gascant · **Posted:** Wed Sep 07, 2011 8:59 pm

FWIW, I recently bought an SOC meter from garygid. Initially, it just showed SOC (% remaining) but, with the latest firmware update, now shows Voltage, current (directional) and Power. I was braking downhill at 45 MPH last weekend and thought I saw 40 kW of regen Power for a brief moment. Then today, having to do a rapid deceleration at a freeway off ramp, it appeared to give 44-45 kW regen Power. So, maybe the 30 kW limit indicated by the energy display in the LEAF is fictitious and arbitrary? Just sayin.... 8-)

Nekota · **Posted:** Wed Sep 07, 2011 9:36 pm

tbleakne wrote:

This is a very nice graph. Do you have a link to the report from which it was extracted ?

It's from a nice article from SAE on Vehicle Electrification with the chart available with the following link.

http://www.nxtbook.com/nxtbooks/sae/11EVSD0223/#/16

Volusiano · **Posted:** Wed Sep 07, 2011 9:47 pm

gascant wrote:

FWIW, I recently bought an SOC meter from garygid.

I guess I missed the memo that garygid sells his SOC meter. Can you point me to the thread that talks about this in more details? I'd like to learn more. Thanks.

91040 · **Posted:** Wed Sep 07, 2011 10:27 pm

Volusiano wrote:

gascant wrote:

FWIW, I recently bought an SOC meter from garygid.

I guess I missed the memo that garygid sells his SOC meter. Can you point me to the thread that talks about this in more details? I'd like to learn more. Thanks.

viewtopic.php?f=44&t=5045&start=0

drees · **Posted:** Wed Sep 07, 2011 11:50 pm

gascant wrote:

So, maybe the 30 kW limit indicated by the energy display in the LEAF is fictitious and arbitrary? Just sayin.... 8-)

It's possible - gary mentioned he's seen more than 80 kW under power.

Or perhaps the two don't necessarily agree.

Or perhaps the gauges only indicate what the maximum sustained power/regen is, but lets the car go briefly over those limits in certain conditions.

tbleakne · **Posted:** Fri Sep 09, 2011 5:58 pm

abasile wrote:

tbleakne wrote:

If I can find a steady grade not quite so steep, with a higher safe speed, where I don't need to apply any brake pressure, I can hopefully get a higher regen efficiency reading.

The road that we use to reach our mountain town (CA-330) seems pretty good for that purpose. When there is not much traffic and the SOC is sufficiently low, it is possible to use ECO mode regen to keep one's speed down with little to no use of the brake pedal. You'll have to come visit!

Andrew, this sounds like an excellent plan. I will contact you to find a mutually convenient time.

I have re-edited my regen report above with some new data that now yields this estimate:
Regen efficiency = (5 clicks/7 clicks) = ~73% +- 7%.

Stoaty · **Posted:** Fri Sep 09, 2011 6:11 pm

tbleakne wrote:

I have re-edited my regen report above with some new data that now yields this estimate:
Regen efficiency = (5 clicks/7 clicks) = ~73% +- 7%.

I assume this is for a one way trip (energy back into the battery, not out again to kinetic energy)? If so, and if the efficiency on the way out is assumed to be 80% (motor alone is 87-95% efficient per Nissan), then the round trip would be 0.73 * 0.8 = 58%

SanDust · **Joined:** Fri Aug 06, 2010 10:54 am **Posts:** 1215

Nekota wrote:

The KW loss going from the battery to the wheels is described by Nissan to have an efficiency range of 87% to 95%

The graph seems to be describing the efficiency of the electric part of the drivetrain.

Herm · **Posted:** Fri Sep 09, 2011 9:51 pm

SanDust wrote:

The graph seems to be describing the efficiency of the electric part of the drivetrain.

Yes, motor and inverter.. then you have the one speed gearbox. the differential and the two halfshafts with their universal joints. Probably 2% mechanical losses and 1% battery losses.

SanDust · **Joined:** Fri Aug 06, 2010 10:54 am **Posts:** 1215

Herm wrote:

Yes, motor and inverter.. then you have the one speed gearbox. the differential and the two halfshafts with their universal joints. Probably 2% mechanical losses and 1% battery losses.

The SAE has published a composite efficiency map for the Volt and the efficiencies ranged between 70% and 88%. The Leaf's shouldn't be that different. http://papers.sae.org/2011-01-0887

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Regen question