Disable temperature to maintain summer type regen in winter

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EVerlasting

Well-known member
Joined
Jul 9, 2013
Messages
86
Location
Morristown, NJ, United States
I have a 2012 LEAF SL. Last winter I noticed that my regen dropped significantly during cold weather. For almost five months I experienced very very low regen even when battery pack SOC was very low. Yes, I had the software update done last year in August 2013. Some people have reported that the reduced regen is a result of this software update while some adamantly argue that its due to battery pack losing capacity. I still have all 12 bars. A friend of mine has a 2013 LEAF SL and during last winter both our LEAFs had almost the same mileage accumulated. He drives much more than me everyday. He claims that he experienced absolutely no reduction in his regen during winter. Regardless of what is causing this regen reduction in 2011-2012 models, is it possible to hack our way out of this problem. The only way LEAF knows its winter is by some external temperature sensor. If we disable the temperature sensor, the LEAF may allow us to drive with full regen even in winter. Does anyone know where this sensor is located and how to disable it or pull out it's fuse? I dont mind living with a DTC warning light all winter, as long as I can drive with full regen. Full regen will definately extend winter's reduced range and allow one paddle driving as we do in summer. It wil also reduce wear and tear on the friction brakes which saw more than usual use during last winter. Any help, suggestions and guidance will be most appreciated. This maybe turn out to be a great hack that most of us will do if its possible.
 
EVerlasting said:
<snip>The only way LEAF knows its winter is by some external temperature sensor. <snip>
Possibly. Perhaps probably. But not necessarily. It may be the result of how the battery responds to cold weather (pack resistance, capacity, etc.). Also, I wouldn't touch a hack like this unless I was sure I would never be eligible for pack replacement. Circumventing Nissan's efforts to prolong battery life will (understandably) void any claim.
 
TickTock said:
EVerlasting said:
<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.
 
My kingdom to whoever can fix the cold weather regen in my 2012. I firmly believe it is a bug in the last software update.
 
One thing I firmly believe to be a bug is: Reducing available regen kW as the vehicle's speed increases.

Even with a relatively warm battery, I don't see as much regen as when the car was new. Some, but not all, of that loss should be expected due to degradation.

I wouldn't mess with the temperature sensor, though. That's asking for trouble.
 
My 2013 SV also has reduced regen in cold weather, so it's not limited to first generation Leafs. I don't find it to be a big problem. They may be concerned about thermal stress - cells expanding more (and quickly) over a very large temp range if full regen is provided when the pack is cold.
 
are we sure its the outside temperature its relating too? I would more likely guess its the internal battery pack sensors you would have to turn off. This makes more sense because it would be the battery temperature not outside temperature that would affect braking. That said, I really don't think you want to touch the internal battery temperature sensors - that seems very difficult and I see batteries being bricked.

But I agree with others here, there was definitely a glitch in the software.
 
I wonder if there is a way to increase regen across the board regardless of the weather conditions? I want full 4 bars of regen anytime I completely lift of the accelerator.
 
EVerlasting said:
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.
2013 & 2014 did have some modest change compared to 2011 & 2012. Some claim it may have been significant, but bit early to be sure.

But I think it is more likely the significant loss in regeneration was a software error. No special effort to slow capacity loss. But the temperature that is causing the loss is more likely pack, than ambient.

When I had my three year battery test I specifically requested that they NOT do the software update.
It is NOT mandatory.
My regeneration is still similar to when it was new.
Seems to be only modest drop off in regeneration due to battery aging.

My only regret in not having the software change is in not being able to provide data for Stoaty capacity degradation model.

Everyone that had P3227 done should be complaining to Nissan frequently through multiple channels. You never know they might fix it.
I still believe what Andy Palmer said, that their intent was to provide the capacity accuracy changes of 2013 forward to the 2011 & 2012.
But 2013 is a lot different. Three pack temp sensors instead of four. Don't report 12V the same.
Would have been easy to mess up 2011 & 2012 "following" the new 2013 code.
 
EVerlasting said:
TickTock said:
EVerlasting said:
<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.
What we know is the car slowly decreases available regen while drawing power from the battery be it to maintain higher speed, accelerate or run the heater (I need to check the heater bit - I don't think it has been proven) and slowly increases regen when regenerating. Pure speculation, but my theory is they were trying to discourage over cycling (charging and discharging over and over) in vehicles driven by tailgaters. If you do a lot of accelerating and braking pushing charge in and out of the battery each cycle adds wear on the battery so they slowly give you more if you request it steadily. What we also know is the available regen range is more than twice that displayed on the dash bubbles (I've seen 9 bubbles worth when only 4 bubbles show on the dash). So when you think you have "full regen" (all regen bubbles) it really just means you have >45% possible regen. This has the effect of magnifying the perceived impact of any reduced regen from the sw udpate (you may have been moving between 90% and 45% before and never seen a bubble drop but now it varies between 90% and 33% which will cause you to see 2 bubbles drop). So a 12% reduction (or 27% depending on how you look at it) looks like a 50% reduction.
 
TickTock said:
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.
 
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.
 
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.
 
EVerlasting said:
TickTock said:
EVerlasting said:
<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.
 
EVerlasting said:
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.
 
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.
 
mynameisjim said:
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.
 
TickTock said:
drees said:
<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 said:
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 said:
mynameisjim said:
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.
 
mynameisjim said:
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.
 
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