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JeremyW
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 12:14 pm

TickTock wrote:Pure speculation, but my theory is they were trying to discourage over cycling (charging and discharging over and over) in vehicles driven by tailgaters.
My speculation is ether Nissan was worried this practice would introduce a lot of error in coulomb counter due to the inaccuracy of the hall effect current sensor AND/OR this practice causes excessive localized heating within the cells or wear in the pack.

I don't think the reduced colder weather regen is a bug. I think it's an intentional band-aid.

Reduced regen due to high speed (or long duration such as a mountain decent) might be Nissan attempting to protect the magnets in the rotor. Excessive regen may cause eddy currents and heat within the rotor which could damage the magnets within the rotor. 2013's have a redesigned rotor that uses less magnets and I wouldn't be surprised if it was a "hybrid" induction/PM rotor to allow these currents to flow without damaging the magnets.
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DaveEV
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 2:27 pm

What is clear is that the Hx value dropped significantly for most after the P3227 update was applied.

Hx appears to be a representation of the packs' internal resistance, this had the side effect of reducing available regen.

I'll re-iterate the things that bug me about regen:

1. Loss of regen at higher speeds. Like abasile I believe the amount of power available for regen should remain constant regardless of speed. I don't believe it has anything to do with the motor - the amount of power pushed through the motor due to regen is only a fraction of the power pushed through the motor under acceleration - and if it were a motor issue, it'd limit regen across the board instead of only cooler temps (instead of hotter temps which is what kills motors) and lower SOC.

2. Loss of regen in cooler weather. This I believe is due to the reduction in Hx - with cooler temps the car thinks the pack's internal resistance is higher than it really is, so further limits regenerative braking.

Combine the two and at 65 mph with the pack at 75-80F (hardly cool temps) and SOC at 70-75% and you only get about 2 bubbles of regen or about 10 kW. Bare enough to slow the car down. When the car was new you'd get 25-30 kW of regen.

It's clear that the pack can handle higher amounts of regen if you simply look at pack/cell voltages under maximum regen as voltages don't get anywhere close to the maximum voltage of 4.1V/cell. I suspect that this winter when the pack gets below 70F again I won't have any significant regen until SOC gets below 60%. 80% SOC will be like the old 90% SOC.

At lower SOC (say 50%) it won't even let the voltage of the cells get up to 4.0V.

I'd love to perhaps use Leaf Spy to collect more information to compare maximum regen across different cars at different SOC.

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TickTock
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 2:44 pm

drees wrote:<snip>Hx appears to be a representation of the packs' internal resistance<snip>
Not really (although I think you may be right that the loss of regen is related to pack resistance).

EVerlasting
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 3:00 pm

All those claiming that Nissan reduced regen to protect the battery or motor or what ever, please care to explain why 2013+ LEAF models don't have that much reduction of regen and instead have the "B" mode's increased regen. Also check out regen in Tesla Model S, BMW i3, and other EVs. They run on batteries too. Nissan screwed our original regen with the software update and haven't bothered to fix it. They never mentioned anything about changes to regen in their software update announcement literature, otherwise I wouldn't have got it done. Until we force them to rectify this software error through a legal battle, someone please find the darn sensor to disable that will restore full regen. Thanks.
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dhanson865
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 3:18 pm

EVerlasting wrote:
TickTock wrote:
EVerlasting wrote:<snip>The only way LEAF knows its winter is by some external temperature sensor. <snip>
Circumventing Nissan's efforts to prolong battery life will (understandably) void any claim.
Why does Nissan want to prolong battery pack life of only 2011-2012 models by reducing their regen in cold temps and at the same time increase regen in 2013+ models with the "B" mode in any temps even though all LEAFs from 2011-2014 models have the same battery pack chemistry. It doesn't make sense. There has been some talk in the software update thread that the update may have a glitch (bug) of reducing temp based regen too much in 2011-2012 by mistake. 2013+ models never needed this software update so they are doing just fine regen-wise in cold weather.
They have similar battery pack chemistry. I guarantee you that a 2013 model has a better chemical profile than the 2011/2012 just not enough to make Arizona cars immune to heat degradation.

We have yet another battery chemistry change for 2015 models and this time they are willing to call it a more significant improvement but don't let their lack of detailed change announcements fool you into thinking there are only two battery chemistries in the Leaf genealogy.
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TickTock
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 3:27 pm

EVerlasting wrote:All those claiming that Nissan reduced regen to protect the battery or motor or what ever, please care to explain why 2013+ LEAF models don't have that much reduction of regen and instead have the "B" mode's increased regen. Also check out regen in Tesla Model S, BMW i3, and other EVs. They run on batteries too. Nissan screwed our original regen with the software update and haven't bothered to fix it. They never mentioned anything about changes to regen in their software update announcement literature, otherwise I wouldn't have got it done. Until we force them to rectify this software error through a legal battle, someone please find the darn sensor to disable that will restore full regen. Thanks.
I think it is just an unfortunate/non-ideal algorithm. It isn't that max possible regen is reduced, it is just harder to realize that max. You can still get "max" regen at freeway speeds in the winter - you just need to be on a long downhill run so you engage regen for longer. I drive a 2011 so cannot comment on how the "B" mode works. If you are driving in this mode, do you have full regen available after quickly accelerating up to speed? Or do you still have to earn it? If they let you have full regen immediately after strong accel, then that does contradict my "prevent excessive cycling" theory.

mynameisjim
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 3:42 pm

I can add a data point for temperature. I use a heated garage in the winter so there are days when my car is 60 degrees but the ambient is much lower and my regen is severely limited. I think the car uses outside air temperature for this calculation based on my experience. I will have 5 battery temperature bars.

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TickTock
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 4:04 pm

mynameisjim wrote:I can add a data point for temperature. I use a heated garage in the winter so there are days when my car is 60 degrees but the ambient is much lower and my regen is severely limited. I think the car uses outside air temperature for this calculation based on my experience. I will have 5 battery temperature bars.
Very interesting. I wonder if some safety feature kicks in once you fall below freezing to ensure traction control can do it's thing if you hit a sheet of ice.

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DaveEV
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 4:33 pm

TickTock wrote:
drees wrote:<snip>Hx appears to be a representation of the packs' internal resistance<snip>
Not really (although I think you may be right that the loss of regen is related to pack resistance).
Well, there you say that Hx is proportional to both ESR (internal resistance) and SOH (capacity remaining).
EVerlasting wrote:Nissan screwed our original regen with the software update and haven't bothered to fix it. They never mentioned anything about changes to regen in their software update announcement literature, otherwise I wouldn't have got it done. Until we force them to rectify this software error through a legal battle, someone please find the darn sensor to disable that will restore full regen. Thanks.
So how many people have actually complained about this? I complained during my last visit to the dealer - but that didn't get anywhere. Anyone else take it to the EV hotline or perhaps Facebook? Perhaps if enough of us did all 3 we might get some traction.

As far as working around the issue, I see a couple possibilities:
1. Spoofing the battery temp sensors to read significantly hotter than it actually is.
2. Spoofing/intercepting CAN bus messages so that the car thinks that more regen is available either through modifying Hx, or some other message. I don't know enough about how this works to know if it's feasible. I think ideally we'd probably reprogram one of the ECUs, but this would take reverse engineering the Nissan Consult software, firmware flashing process and firmware.
TickTock wrote:
mynameisjim wrote:I can add a data point for temperature. I use a heated garage in the winter so there are days when my car is 60 degrees but the ambient is much lower and my regen is severely limited. I think the car uses outside air temperature for this calculation based on my experience. I will have 5 battery temperature bars.
Very interesting. I wonder if some safety feature kicks in once you fall below freezing to ensure traction control can do it's thing if you hit a sheet of ice.
Should be easy to verify by logging the available regen parameter and other various parameters.

EVerlasting
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Re: Disable temperature to maintain summer type regen in win

Fri Aug 08, 2014 8:44 pm

mynameisjim wrote:I can add a data point for temperature. I use a heated garage in the winter so there are days when my car is 60 degrees but the ambient is much lower and my regen is severely limited. I think the car uses outside air temperature for this calculation based on my experience. I will have 5 battery temperature bars.
I also think it is the outside (ambient) temperature sensor that limits regen when it is cold. I used to park my LEAF in an unheated garage but it was still about 20 degrees warmer inside the garage than outside. When I used to start my LEAF and back out of my garage I would have full regen (all four regen circles activated) but as soon as I started driving in the outside air, I would get the Snowflake icon warning "Outside Temperature Is Very Low" and immediately my regen would decrease.
2012 Nissan Leaf SL|25,000 miles
Weekly charging using public CHAdeMO station 7 miles from my condo apartment and occasional charging using EVSEupgrade L2 240v 12 amps. 11 capacity bars

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