Or, Why it’s important to read the owner’s manual
A look at a very popular LEAF forum (mynissanleaf.com) will show that currently the most active topic is about the battery capacity loss of the LEAF. To clarify, we are talking about the traction battery, or the battery pack used to power the electric motor, as opposed to the 12-volt battery, which is used to power vehicle accessories. We have had many readers express interest in this topic and wanted our view on it. Our intent was to read through all of the posts, analyze them, and write a comprehensive article on the subject. When we started reading the posts, there were about 60 pages or 600 posts. It has since grown to over 1700 posts and counting. Our original plan was to read every post so we didn’t miss an important detail and then write up our review of the situation. However, given the rapid growth rate of the thread, we’ll start writing about this topic now in segments and update our series as we read more posts, and more information becomes available. That said, we choose to start our series on the care and feeding of the Nissan LEAF battery, as it became apparent upon reading the posts of the first several individuals that showed reduced capacity, that many had seemingly neglected to do so. Bear in mind that we don’t know what the charging routines and maintenance activities were for all individuals with battery capacity loss issues, but there was some commonality among the first five. But before we get to the battery capacity loss issue, we wish to take a look at the Nissan LEAF owner’s manual to see what Nissan recommends regarding battery care and maintenance.
As the current model is the 2012 Nissan LEAF we will use that owner’s manual as our reference.
In the EV Overview introductory section on Page EV-2 we find this notice:
One significant change from the 2011 model year LEAF to 2012 was the inclusion of a battery heater as standard equipment. The battery heater is designed to maintain Lithium ion (Li-ion) battery output in extreme low temperature environments. Here is the notice regarding the Li-ion battery heater (Page EV-5):
The Lithium ion battery warmer uses electrical power from the Lithium ion battery when the charger is not connected to the vehicle. However, if it gets really cold where you live, leave the LEAF on the charger, otherwise the battery heater will not work if the Lithium ion battery charge falls below 30%.
Extreme hot temperatures, even for periods as short as one day, may impact battery capacity loss. The effect of extreme cold temperatures can be mitigated to some degree by the use of the on board Li-ion battery heater.
Li-ion Battery Life
Nissan notes over a dozen specific situations or operations that should either be avoided or performed to optimize Li-ion battery life. These are the specifics straight from the owner’s manual (Page EV-23):
NISSAN recommends you use the following driving and charging habits, where possible, to help maximize the battery’s useful life:
- Avoid exposing a vehicle to ambient temperatures above 120°F (49°C) for over 24 hours.
- Avoid storing a vehicle in temperatures below −13°F (−25°C) for over 7 days.
- Avoid leaving your vehicle for over 14 days where the Li-ion battery available charge gauge reaches a zero or near zero (state of charge).
- Allow the vehicle and Li-ion battery to cool down after use before charging.
- Park/store your vehicle in cool locations out of direct sunlight and away from heat sources.
- Avoid sustained high battery temperatures (caused, for example, by exposure to very high ambient temperatures or extending highway driving with multiple quick charges).
- Use the normal charging or trickle charging methods to charge the Li-ion battery and minimize the use of public Fast Charge or Quick Charger.
- Avoid sustained high battery state of charge (caused, for example, by frequently charging to 100% state of charge and/or leaving the battery above 80% state of charge for long periods of time).
- Allow the battery charge to be below at least 80% before charging.
- Moderate driving.
- Use of ECO mode.
- NISSAN recommends charging the batteries using the long life mode unless the vehicle is going to be driven a long distance. See “Charging timer” in the “CH. Charging”section.
- If the vehicle will not be used for an extended period of time, charge the Li-ion battery using the long life mode once every 3 months. Do not operate the charging timer repeatedly while the charge connector is connected to the vehicle after the Li-ion battery charging is completed. Doing so may discharge the 12-volt battery. The power of the Li-ion battery can be checked on the Li-ion battery available charge gauge. See “Li-ion battery available charge gauge” in the “2. Instruments and controls” for details.
Before we go further, we understand that no situation exists where an owner would be able to accommodate all of Nissan’s recommendations. Some of these items, are in fact, beyond the control of the vehicle owner. We would like to point out a couple of things about this list. Although the first bullet point talks about high ambient air temperature, several points later Nissan cautions against sustained high battery temperatures. While intuitively it might seem that a black, unvented steel case would make for a very high battery temperature, there are other factors at play. First, the battery pack weighs about 660 pounds. This is very dense weight, as opposed to something like 660 pounds of feathers, which would weigh the same but take up quite a bit more room. What this means is that the starting temperature of the battery pack influences the ultimate temperature due to the inertia involved. Kind of like turning an aircraft carrier moving at speed. It takes awhile to change course. The flip side of that is that once a high battery temperature has been achieved, it could take some time to cool down. Other battery temperature factors could include sustained aggressive acceleration or DC quick charging, which is why Nissan cautions against quick charging too often (Hat tip to Stoaty for the battery temperature info). Other points worth noting that can be controlled by the vehicle owner are the avoidance of sustained high battery state of charge (such as frequent charging to 100% or leaving the battery above 80% for long periods of time), and allowing the battery state of charge to fall below 80% prior to charging. The long life mode referred to recommends the use of the LEAF’s on board charge timer set to limit charging to 80%.
Our next article in the series will look at the first 250 posts or so, which encompass the first five owners to acknowledge publicly on the My Nissan LEAF forum the loss of one battery capacity segment. Future articles will take us further into the discussion and offer a look into some of the other owners that have experienced LEAF battery capacity loss.
As I finish writing this I see that Nissan has posted an open letter to LEAF owners on the MNL forum. We will include Nissan’s response to this issue, and our analysis of that response, in a future article.