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Nissan says greater than average battery capacity loss due to mileage and temperature

Nissan Senior Vice President, Research & Development–Nissan Americas, Carla Bailo sent an open letter to the LEAF community summarizing the company’s initial findings on reports of battery capacity loss expressed by a number of owners in the Phoenix market. (Earlier post.)

Bailo said that Nissan identified seven LEAF owners in the Phoenix area who had reported concerns with their vehicles. Nissan brought the cars to its Arizona test facility, removed the batteries for evaluation, measured capacity, and conducted voltage testing on individual battery cells. These tests were diagnostic only; no modifications were performed to the battery packs themselves.

Nissan then analyzed the results with specific emphasis on the rate of actual capacity loss for each vehicle. The goals of the testing were to determine:

  1. if there were any defects in materials or workmanship in the individual batteries or vehicle systems;

  2. if the batteries were performing to specification; and

  3. their performance relative to the global LEAF population.

Overall findings were:

  • The Nissan LEAFs inspected in Arizona are operating to specification and their battery capacity loss over time is consistent with their usage and operating environment. No battery defects were found.

  • A small number of Nissan LEAF owners in Arizona are experiencing a greater than average battery capacity loss due to their unique usage cycle, which includes operating mileages that are higher than average in a high-temperature environment over a short period of time.

While we understand that some LEAF owners are concerned about battery capacity loss, we want all owners to remember that all battery-electric vehicles—and all lithium-ion batteries—demonstrate capacity loss over time. So while your LEAF may have been able to travel a certain distance or more on a charge when new, its range will decrease as the battery ages, miles accumulate and gradual capacity loss occurs. This loss in capacity will occur most rapidly in the early part of your battery’s life, but the rate should decrease over time.

...It is also important to put the scope of these concerns in perspective. Globally, there are more than 38,000 Nissan LEAFs on the road that have travelled more than 100 million zero-emission miles, and we expect these vehicles, in normal operating conditions, to retain 80 percent of battery capacity after five years. As each user’s operating characteristics are unique and many factors impact battery capacity, we can expect some vehicles to have greater than 80 percent capacity at five years, and some vehicles to have less.

In Arizona, we have approximately 450 LEAFs on the road. Based on actual vehicle data, we project the average vehicle in that market to have battery capacity of 76 percent after five years—or a few percentage points lower than the global estimate. Some vehicles in Arizona will be above this average, and some below. Factors that may account for this differential include extreme heat, high speed, high annual mileage and charging method and frequency of the Nissan LEAFs in the Phoenix market.

Comments

EVryman

I am utterly disgusted that my post was removed. There was nothing in it that was offensive other than stating facts. I am PARTICULARLY offended that no word was sent to me that it HAD been removed nor why. Great job. That was sarcasm.

Engineer-Poet

It was probably a glitch with Wordpress.  MM seldom pays attention to comments.

Engineer-Poet

I forgot to say that there is a filter which will delete comments if they contain certain keywords; you will see them "published", but if you refresh the page they are gone.  That's automated and MM appears to have little control.

Roger Pham

After re-reading this article, it seems that those who live in Arizona who drive longer distances in high ambient temperatures are experiencing higher-than-average loss of capacity, while those who drive less don't. This seems to indicate battery overheating, and the longer one drives, the more heat will accumulate and the hotter the battery will get, unless actively cooled by the on-board A/C system. Perhaps a better battery cooling system, as Harvey D suggested, can be the key to address this problem.

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