Braking regen issue

[rainnw]

I was told today that the battery charging rate indeed slows at above 80% and again above 90%; that this is to control battery heating.
In addition, there would be further slowing of the charge rate through the Blink when the temperature is high in your garage to deal with battery heating.

I was told that both the Blink and the car do this.

Who told you the Blink unit varies the pilot signal based on temp?

Since the Blink is not the "charger", i don't see this happening. Its completely unnecessary.

The on board 3.3kW charger will regulate battery charging rate based on temperature, but it slows at 80% because this is how you treat the battery chemistry nicely. This has nothing to do with being concerned about temperature. If you just jam whatever the pack will take up to 100% (done this quite a few times), it will damage battery chemistry over time.

 

[abasile]

I took my first Leaf run up the Mt Baldy road to Baldy Village above Claremont...

Thank you for the drive report! Are you going to try driving all the way up to the Mt. Baldy ski lifts next time?

 

[zigadabooga]

So, to maximize mi/kWh as reported by Carwings, charging to 80% SOC is the way to go.

Also, is this why the L3 is "80% charge in 30 minutes"?

I wonder if 'Fujitaxi' charges to 80% to get the high rankings in mi/kWh.

 

[LEAFfan]

So, to maximize mi/kWh as reported by Carwings, charging to 80% SOC is the way to go. I wonder if 'Fujitaxi' charges to 80% to get the high rankings in mi/kWh.

Charging to 80% or 100% has nothing to do with your m/kwh. And some people believe that charging to 80% will extend battery pack life. This hasn't been proven.
Fujitaxi gets his high m/kwh ranking by spinning his wheels without going anywhere. There is no other way to get over 100m/kwh without doing that.

 

[abasile]

Charging to 80% or 100% has nothing to do with your m/kwh.

Not necessarily. At higher SOCs, regen is limited. Living on a mountain as I do, I need to start with an SOC below 80% if I want to pick up maximum regen (thereby maximizing miles/kWh) when driving down to the valley floor. This is a somewhat dramatic example, but it illustrates the point. Driving on flat ground, however, you'll only notice diminished regen when really close to 100% SOC.

 

[LEAFfan]

Charging to 80% or 100% has nothing to do with your m/kwh.

Not necessarily. At higher SOCs, regen is limited. Living on a mountain as I do, I need to start with an SOC below 80% if I want to pick up maximum regen (thereby maximizing miles/kWh) when driving down to the valley floor. This is a somewhat dramatic example, but it illustrates the point. Driving on flat ground, however, you'll only notice diminished regen when really close to 100% SOC.

Yes, but he was talking about a person in Japan, where it is relatively flat like here. I could still easily get my 6+m/kwh while charging to 100%. There have been numerous posts about using 80% for regen down hills, so that's a given.

 

[zigadabooga]

When I was referring to Fujitaxi, I was saying he must be charging to 80% SOC because immediate regen would decrease the daily kWh used in calculation, thereby increasing mi/kWh calculated.

At lease that's what I have to assume.

You see, I drove 50.3 miles and charged that night with 14.97 kWh. Making (50.3 mi) / (14.97 kWh) = 3.36 mi/kWh

My Leaf said I was around 4.1 mi/kWh.

If Carwings/Nissan/Leaf is reporting (50.3 miles) / (14.97 kWh + XX.XX kWh from regen) that would equal a lower mi/kWh, not higher.

The only way to explain higher economy is either:

1) Carwings/Nissan/Leaf is lying to pad numbers

or

2) Regen kWh is deducted from the kWh total

I'm inclined to test the second option,

So, reverse calculating: (50.3 mi) / (4.1 mi/kWh) = 12.27 kWh

It took my 14.97 kWh to charge it although maybe 0.74 kWh or so is from 5% charging loss, equaling 14.22 kWh to the battery.

Then, (14.22 kWh) - (12.27kWh) = 1.95 kWh regenerated.

I can go further and say I get an average of 15 kW in half regen capacity so,

(1.95 kWh) / (15 kW) = 0.13 hours or 7.8 minutes of cumulative breaking, this sounds reasonable for a 50.3 mile commute lasting 1.5 hours of light traffic (approx 33mph).

 

[tps]

If we take the pessimistic value of 20 usable kWh in the battery, then the 20% going from 80 to 100 represents 4 kWh. Now if I can find a hill big enough to give me a full minute at 30kW regen, that works out to 1/2 a kWh. Doesn't sound like a threat to my battery. But I have to assume they know things that I don't.

Please re-read your own post. You postulate the regen charging a nearly full battery at a rate of 30 kW! This quick-charging territory, definitely a threat to a nearly full battery pack. Even the 3.3 kW on-board charger tapers to lower charge rate as the battery nears full charge to protect the battery pack. This is why Nissan effectively disables regen to when the pack is nearly full.

 

[tbleakne]

I took my first Leaf run up the Mt Baldy road to Baldy Village above Claremont...

Thank you for the drive report! Are you going to try driving all the way up to the Mt. Baldy ski lifts next time?

Yes. On Monday, Aug 1, I did the Baldy run again. Starting from home with a full 12 bars, my progress was as follows, driving at the posted speed limits, with care:

Padua traffic light at the base, 0.0 mi, 1.8Kft, 11 bars
Baldy village, Glendora mt. rd, 7.4 mi, 4.2Kft, 8 bars
Ice House Canyon, 9.3 mi, 4.9Kft, 7 bars
Snow Crest Lodge, 11.3 mi, 6.0Kft, 6 bars
Ski Lift, 12.1 mi, 6.5Kft, 5 bars -> 4 bars (after cycling pwr off, then on).

On the return trip down I did my best to get maximum regen and minimize friction braking.
The 5th bar returned almost immediately,
The 6th bar returned 3.7 miles down from top
The 7th bar returned just before the bottom Padua traffic light.

23 miles and 4.7Kft up and down on about 4 bars net. Not bad. I say "about" because when you first get a bar back, it is not a full bar, right?

When I get a chance, I will use this data to help calibrate my spreadsheet model for predicting delta SOC.

 

[tbleakne]

Before I did the Baldy run reported in my previous post, I used my TED to watch the charge taper off as it reached 100%. I know this was done many months ago, but I never could find the data, so I am posting my own here.

As others in this thread have noted, the charging taper is relevant to the decline of regen. Since the L2 charge is much slower than the maximum 30KW of regen, we would expect charging taper to start later, and that is what I observed, but I was still a little surprised at the results.

For most of my charge cycles, when I start with 5-7 bars of charge, the car's estimate of time to reach 100% is much too long, sometimes by almost a factor of 2. This has made it difficult to use charging time to aim for a specific SOC level, such as 70%, 90%, 11 bars, etc.

Before starting charge: 6 bars, estimate to 100%: 3:30
Set charging timer for 2:10 (2 hours, 10 min) -> result after charge:
11 bars, estimate to 100%: 30 minutes.

I resumed charging, now watching TED. I expected the estimate to be high, and the taper to begin very soon. Instead there was 30 minutes of full 3.8KW wall charging power. Then the taper began, gradually scaling back the power over the next 15 minutes. During this period the power would fluctuate up and down 20% or so for periods of perhaps .5 min as it tapered down to 3.3KW, 3KW, 2.5KW, 2KW, 1.8KW, and then it stopped. The power never dropped to zero before the end.

Estimated total power delivered from the wall during this trapezoid-shaped taper:
2.8KW av * 1/4 hr = .7KWhr.

 

[abasile]

On Monday, Aug 1, I did the Baldy run again. Starting from home with a full 12 bars, my progress was as follows, driving at the posted speed limits ...

Thank you for the additional data! If I recall correctly, isn't the speed limit 45 or 55 on Mt. Baldy Road below the Village, and 40 or so above the Village? If so, then I expect your motor power would have been fairly high on the climb, which based on my experience might have cost an extra bar or so. (Perhaps your spreadsheet predicts this.) In the future, when climbing to the Baldy ski lifts, it seems that it would be quite feasible to start at your house with 80% SOC or less, particularly if one drives below the speed limit.

I have yet to see three bars of regen on a descent! Were you doing the speed limit on the way down, or going slower?