Battery temp

[lobbers]

Just about to buy new Leaf. Can anyone comment on battery temperature issues in Australia (Brisbane).

What about on 38 degree Celsius days?

Thanks

[Phoebe]

I've had my LEAF nearly 7 years and I've always parked it in the shade.  I've still only lost 2bars from my battery.  It does seem to make a difference.  Degradation happens faster in the hot weather, so it's worth avoiding it where you can.  I believe the 2nd generation  LEAF survives hot weather better than 1st generation LEAF like mine.

[lobbers]

Thanks for your interest Phoebe. I have watched a few videos recently about temperature rises in the battery after charging and also while travelling.
These videos were made in the UK where the ambient temperature is a lot less that I experience here,
so I am interested in owners experiences in Australia.

[johnmath]

The Leaf has a passive battery cooling system which works fine when the car is in motion with air directed under the body past the battery pack. During charging there is no cooling as there is no airflow over the battery pack. Charging heats the battery and rapid charging heats the battery much more than slow charging.

Our Leaf is a JDM import that is 3 years old and had 30,000km on the odometer. The battery health was ~85% at 30,000km indicating some loss of battery performance. It had only ever been rapid charged according to LeafSpy. Since we've had the vehicle it has only been charged (except once) with slow charging at ~3.6kW or less whenever practicable. The rate of capacity loss of the battery in our ownership is only one third of the rate of capacity loss during the 30,000km when rapid charging was used.

My suggestion is to use rapid charging only if you really need to, and especially avoid it on hot summer days.

[lobbers]

I placed order for new Leaf yesterday in Brisbane. Looking forward to taking delivery next week. I also have a 6Kw solar system on my house so will be interested in how that performs. I am retired and can charge during the day, for zero cost I hope. My original query was about high ambient temperatures and how that could effect the performance and degradation of the battery.

[rusdy]

Aug 15, 2019 6:59:35 GMT 11 lobbers said:

I placed order for new Leaf yesterday in Brisbane. Looking forward to taking delivery next week. I also have a 6Kw solar system on my house so will be interested in how that performs. I am retired and can charge during the day, for zero cost I hope. My original query was about high ambient temperatures and how that could effect the performance and degradation of the battery.

Congrats! As long you don't leave your Leaf in the heat AND fully charged, your car should be OK. Heat is inevitable here in Oz of course, so when that happens, make sure the car is half charged or less. If you need to drive long distance during the heat, ensure don't leave at fully charged state for too long (i.e. use it immediately).

After reading many white papers (although not specifically to Leaf battery, but I believe still representative), my naive understanding:

• The 'fully charged' threshold can be as low 50-ish% State of Charge 
  
• 'Heat' can be as low as 30-ish degree celcius
  

When both thresholds above are met, battery degradation worsen exponentially (depending the time spent above thresholds).

In short: fully charged and heat is the problem.

I do wish user hieronymous is still here. He's the only one I know of in the past deliberately kept his leaf in low SOC (under half) at all times. Also, living in NZ definitely help. I would love to know his battery stats now.

[johnmath]

The lithium ion battery cells in a BEV are heated by the passage of electrical current through the cell, both when charging or discharging the cell. The Leaf has passive battery cell cooling, and during driving the cells are cooled by airflow channeled under the vehicle, however during charging when the car is stationary there is no airflow to cool the batteries. There is a 'design limitation' with the Leaf battery pack in that some cells are enclosed on all sides by other cells.

The "normal" or safe operating cell temperature range for the type of batteries in cars like the Leaf is -20 to +60 degrees Celsius. As far as I am aware there is no mechanism by which weather extremes alone causes battery degradation.

The cell heating which occurs when current flows through the battery is exacerbated by high currents. Driving the car at normal speed in normal weather isn't going to cause the battery to heat up much, nor is charging with the normal Type 1 or (J1772 plug) which is limited to the capacity of the on-board charger, namely 3.3kW or optionally 6.6kW for some US and UK delivered Leafs.

When fast charging with the CHAdeMO plug, the middle cells can't cool as effectively and will heat up the most - they are the ones that will age prematurely. The last 20% of charging dissipates more heat so fast charging is best terminated at 80% charge for battery longevity. Fast charging is best avoided altogether or only used when there isn't an alternative.

I believe charging to 100% occasionally is important for battery longevity as it keeps the individual cells balanced. Charging to 100% should be done at slow charging (Level 1 or 2) rates. Once an individual cell achieves 100% charge, a bypass resister is switched in to shunt some current around that cell to prevent it overcharging, whilst other cells catch up. The maximum range is achieved when all cells are balanced.

[lobbers]

John, thanks for the information, very helpful, I am looking forward to getting the car next week. Do you use Leaf Spy?. From what I have read, it seems to be the tool of choice to use to keep track of battery health. There seems to be a lot of choices when it comes to the OBD 2 adapter, can you recommend a particular model?. I use an Iphone.

[johnmath]

I have LeafSpy for iPhone. I bought the iCar WiFi OBD2 adapter because of its small size. I don't think BlueTooth adapters work with LeafSpy on iPhone. The downside of WiFi over BlueTooth is you may need to select the network on your phone to use it - no big deal really. I got the iCar for its small size thinking I would leave it plugged in all of the time, however I find I need to unplug and replug it each time I want to use LeafSpy because the adapter doesn't 'wake up' otherwise, even if I press its power button. After the novelty of looking at all the data had worn off, I find I don't use LeafSpy much at all. I guess it was worthwhile to be able to get a baseline on the car's battery health as purchased and also to see there were no fault codes logged on the OBD2. Here's a trip log showing speed and elevation:

[lobbers]

Aug 17, 2019 10:58:02 GMT 11 johnmath said:

I have LeafSpy for iPhone. I bought the iCar WiFi OBD2 adapter because of its small size. I don't think BlueTooth adapters work with LeafSpy on iPhone. The downside of WiFi over BlueTooth is you may need to select the network on your phone to use it - no big deal really. I got the iCar for its small size thinking I would leave it plugged in all of the time, however I find I need to unplug and replug it each time I want to use LeafSpy because the adapter doesn't 'wake up' otherwise, even if I press its power button. After the novelty of looking at all the data had worn off, I find I don't use LeafSpy much at all. I guess it was worthwhile to be able to get a baseline on the car's battery health as purchased and also to see there were no fault codes logged on the OBD2. Here's a trip log showing speed and elevation:

I will probably end up doing the same, use it for a while and then only use it infrequently, but I would like to get benchmark information for future references in case I have to go back to Nissan.I would probably not leave it plugged in anyrate so the problem disappears. Thanks for your help.

[seb]

Hey Johnmath. How did you get that plot on leafSpy?
Also, didn't they have degraded battery life issues with temperature with the earlier 2012/2011 models?

[johnmath]

On one of the LeafSpy pages (#2) you tap the middle of the screen to scroll through 5 graphs; it's the forth one. I think it plots the elevation data from the iPhone GPS.

Early Leafs had the battery changed after some heat issues in Texas and Arizona. I haven't seen detail of what the changes were. It could have been chemistry (adding an element to improve high temperature tolerance) or improved airflow for cooling, or both.

The battery has a large thermal mass and its temperature changes only slowly with the ambient air temperature, which sets the baseline for the battery's temperature. Heat is added to the baseline temperature depending on how hard you drive or charge the car. Regardless of which battery, don't thrash the car in hot weather, don't fast charge unless absolutely necessary, only charge to 80% when practical and keep the car in the cool when parked if possible.