D mode stays on even while on B mode

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estomax

Well-known member
Joined
Jan 20, 2017
Messages
326
Location
Seattle
Hey Guys,

i noticed this the last couple of times i drove my Leaf, but when i start with a full charge, then even in B mode it never actually goes to B mode once a little bit of battery wears off to allow more regen. i can switch between D and B and there is no regen difference at say 40 mph (while usually there should be a large difference). power cycling the car seems to fix this , but i was wondering if anyone else has noticed this?

cheers,
Marko

edit: bringing more info to the first post. First, this happens at various SOC levels, it is normal for the car to not regen during high SOC, but this happens even at 30% SOC, when regen should function fully. i also once noticed that even though the B mode functioned correctly, the brake pedal regen did't work (pressing the brake didnt increase regen). All these symptoms are intermittent and happen once or twice during a long drive, so not very easy to reproduce. One more symptom to the list is that cruise control disengages on its own, randomly, has happened 3 times in the last week where i use it maybe once per day when traffic allows. The battery voltage at rest is 12.6V so unlikely that the aux battery is going bad.

here are the latest errors:
QBLxclo.png
 
Can't say I've noticed it as I seldom charge to 100%, but it makes logical sense since regen is charging the battery pack at a rate of up to 30kW.

If regen was permitted when there's a high state of charge already, then individual cells could end up being over voltage - not good. I'm no expert with LION batteries, but I suspect this is a prudent measure to avoid damage to the battery.
 
Max regen is reduced at high states of charge. I don't know what the limit is, but at 99%+ I can only get one dot of regen, at 98% I can start to get two dots, and after that I'm usually on the highway so I haven't gotten to test any others. I think by 90% it's back to full regen available. Unfortunately that makes braking at high states of charge really weird in comparison to braking at other charge states, so I have to remember to drive differently in the morning than in the evening.
 
At full regen rate (30 kw), 1 min of braking at that rate would add 0.5 kWh of energy to the pack battery.

So, 0.5 kWh / 21 kWh is about 2.4% of pack charge added per minute of MAX regen.

Given that max rate, one would have to be doing a lot of braking to significantly charge the pack.

So, I don't get why Nissan chose to be so conservative with limiting regen at low 90% SOC. I guess they just wanted to be sure no individual cells would be over voltage...
 
And the worst part is as your battery degrades, it gets much worse :(
Just when you could use the extra regen from a degraded battery pack, you basically get none :x
My '12(missing 2 bars) has zero to little regen, even as low as 30% SOC! My '13(full bars) has more regen at 95% SOC than my '12 at a low SOC!
 
Regeneration is limited by maximum allowable cell voltage (or pack voltage if pack is well balanced). This means that high SOC, low battery temperature, and higher internal resistance of deteriorated battery all contribute to reduced regeneration. The lithium battery controller (LBC) limits maximum cell voltage so it limits the regeneration at high SOC to avoid over voltage of the highest cell. If the pack is well balanced, the total pack voltage will be higher before the highest cell reaches the maximum so the LBC allows more regeneration.
 
sorry, i think my post was unclear. At full charge this is expected, but i am noticing this when i am at 30% charge near the end of my trip this morning for example.

maybe i need to plug in with leaf spy and see if i have some unbalanced cells.. but my SOH is very high and i made a 63 mile trip this morning with 23 miles to spare when i got to my destination (80% interstate 60-65mph, albeit with some traffic here and there). just a strange gremlin in the software is what i think.
 
Going off what gerryAZ said then, it sounds like you have a few cells that are a much higher SOC%(or voltage) than the rest, limiting your overall regen....not sure why this would be the case, other than if your battery is quite a bit out of balance. Do you regularly or have you lately charged your Leaf up to 100%? Apparently it should be fully charged occasionally to balance the individual cells, sounds like your pack is out of balance.
 
i charge to 100% with L2 almost every day. next time it does this i will have to plug in my obd dongle and leafspy to have a look.

are there any trouble codes that get stored with that?

cheers
Marko
 
ok it did it again today, similar to yesterday morning, when my range was around 30 miles on the GOM (today was exactly 31% also, i looked on the % gauge). I was going down a hill and felt the regen fall off and the car would only regen at 10 while coasting down a hill.

i threw leafspy / obd dongle at it when i got to my destination and this is what it showed me before i shut the car off (this B-mode dropout happened half a mile from my destination).

7KyG9Tf.png

NJEm1iF.png


this definitely did not use to happen during the winter when i was driving it to work and back and getting the range below 30 on the GOM.

going to start googling those codes now.

Marko

PS, after completing my visit and getting in the car, i drove home with B mode with no problems, (about 10-15 miles), so powercycling took care of the bug / lockout.
 
You have some CAN Bus communication errors so I suspect there are issues with the various modules sharing information. If there are communication errors, the car may default to reduced regeneration (I am speculating here). Try clearing all of the DTC codes before driving again to see if that clears your issue.
 
so a small update after a week. i noticed this happened once more on a 60 mile drive at around 90% charge (at this point regen is fully functional usually), where regen in B mode was the same as D mode,, but the problem corrected itself later on in the drive around 60% battery charge remaining.

Today i noticed a different symptom, D and B modes behaved normally so i got more regen in B mode than D mode, but when i would use actual brakes, it would not add any extra regen, no matter the speed at which i do it (25+ mph braking always adds regen to max it out but it was not doing it today, it only scaled the regen as if i had my foot off the brake when i was coming to a stop).

wierd stuff.. i scanned the car again after clearing the codes last weekend:
QBLxclo.png


is stuff like this covered under the warranty? i am not sure i feel like paying to have this fixed but my car was first registered 12/2013 so it is a very late 2013 model. (mfg 11/13). it even has a 2014 paint code (tri coat pearl white).

I assume I have the original 12v battery so it could be that it is slowly dying, though the car sees the charger every day and has the solar panel which sees sun most days.

thanks,
Marko

Edit: quick look through user manual says replace VCM and then replace PDM after some diagnostic, didn't dig too much further into it but sounds like expensive dealer only replaceable stuff (vehicle control module or power delivery module).
 
I didn't read back. Have you checked the 12 volt battery's rest voltage? Assuming it's ok, it looks to me like a control system error is popping up, and that should be covered over the EV system warranty - I think.
 
estomax said:
just to clarify, rest voltage would be checked with the car powered off and not on the charger right?

Yes. The best way to do it is to shut the car off after unlatching the hood (so you don't need to open the doors again) and after 15-60 minutes open the hood and check the 12 volt battery voltage. If it's under 12.4 that may be at least part of the problem. If it's 12.5 or better it's ok.
 
Since the CAN Bus errors are just related to the EV system, I doubt that the problem is due to a low 12-volt battery, but check the 12-volt battery after charging the car and before driving. Release the hood and lock the doors before plugging in to charge. After charging is complete, unplug charger and wait 15 minutes. Measure the voltage at the terminals of the 12-volt battery with an accurate meter. I would replace the battery if it is not at least 12.4 volts. If the battery is good, let the dealer take care of it under the EV system warranty.
 
If you want to catch errors due to a low 12 volt battery, then checking the rest voltage after charging may mask a marginal battery. Better to check the rest voltage after driving and before the next charge...?
 
estomax said:
Hey Guys,

i noticed this the last couple of times i drove my Leaf, but when i start with a full charge, then even in B mode it never actually goes to B mode once a little bit of battery wears off to allow more regen. i can switch between D and B and there is no regen difference at say 40 mph (while usually there should be a large difference). power cycling the car seems to fix this , but i was wondering if anyone else has noticed this?

cheers,
Marko


This is unusual since my B mode works all the time and I don't use D mode (unless in Cruise control which is very rare)
 
jjeff said:
Going off what gerryAZ said then, it sounds like you have a few cells that are a much higher SOC%(or voltage) than the rest, limiting your overall regen....not sure why this would be the case, other than if your battery is quite a bit out of balance. Do you regularly or have you lately charged your Leaf up to 100%? Apparently it should be fully charged occasionally to balance the individual cells, sounds like your pack is out of balance.

the reason is higher cells take on much more of the power than lower cells and lower cells discharge a greater amount than higher cells so its like burning the candle at both ends. This is why balance is so important.

remember your pack is only as good as its weakest cell
 
estomax said:
sorry, i think my post was unclear. At full charge this is expected, but i am noticing this when i am at 30% charge near the end of my trip this morning for example.

maybe i need to plug in with leaf spy and see if i have some unbalanced cells.. but my SOH is very high and i made a 63 mile trip this morning with 23 miles to spare when i got to my destination (80% interstate 60-65mph, albeit with some traffic here and there). just a strange gremlin in the software is what i think.

First off; you should edit your post for clarity because comments buried below often get missed. I always drive in B mode even at full charge. The level of regen will consider the SOC of the pack before it looks at what drive mode you are in.
 
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