Honda's fix for prematurely dying Civic hybrid batteries hurting fuel economy, performance?

2008 Honda Civic Hybrid – Click above for high-res image gallery

Until the past year or so, the Civic Hybrid had been by far the best selling gas-electric model introduced by Honda. However, the second-generation model introduced in 2006 has not been entirely problem-free. There have been several lawsuits against Honda claiming that the Civic doesn't meet its advertised mileage claims. While those sort of claims are often dubious given their dependency on factors like driving style, climate and terrain, premature battery failures are not.

According to the Los Angeles Times, it appears that 2006-2008 Civic Hybrid models are suffering an abnormally high rate of battery failure at relatively low miles. The nickel-metal-hydride batteries are evidently prematurely losing their ability to hold a charge – particularly in hot weather areas like Arizona and when used in a lot of stop-and-go traffic. The Civic Hybrid has a dual compressor air-conditioning system with an engine driven primary compressor and a smaller electric compressor to keep the system going when the engine is shut during a stop. Using the air conditioning will cause the battery to go through more charge cycles, eventually wearing it down. Read on after the jump for more on why the battery might be failing and how Honda is attempting to address it.

Update: Honda spokesman Chuck Schifsky let us know that the software updated for the 2006-8 Civics is based on the changes that were introduced for the refreshed 2009 models. The 2009 models apparently also got an updated battery but obviously that change isn't going into the older cars. The original 2006-8 models would spend a lot of time during hot weather use with the A/C on which apparently caused the charge cycling rate to increase wearing down the battery.

Update 2: Honda confirmed that the battery pack did change from 2008 to 2009 but its not clear exactly what was updated.

Photos Copyright ©2008 Sam Abuelsamid / AOL

[Source: Los Angeles Times]

Having the battery die prematurely during use in areas with a lot of stop-start traffic is particularly problematic, as this is the duty cycle where hybrids provide the most benefit. By utilizing regenerative braking and idle-shut-off, hybrids can dramatically reduce fuel consumption in an environment where cars often register significantly worse fuel efficiency.

Of course, all rechargeable batteries eventually degrade over time – especially if they are overcharged or over-depleted. Automakers deliberately cycle these batteries only between about 35 and 85 percent charge in order to ensure they last at least through the eight year warranty mandated by the state of California. For its part, Honda has not revealed the root cause of the apparent problems with the Civic. It's possible that the Japanese automaker went with a new chemistry for the second-generation Civic hybrid or expanded the battery operating range in hopes of getting better EPA and real world mileage numbers.

Because batteries heat up when being charged, it's also possible that this is an issue with the battery cooling system. The Civic, like all current hybrids uses an air-cooled battery and and it's possible that in hot environments, it's simply running too hot. Whatever the cause of the premature degradation, Honda is apparently reluctant to replace the batteries.

While Honda won't reveal its cost for the Civic battery pack, the retail price is $2,100, which would be a significant hit to Honda's bottom line if it had to replace all 100,000 Civic hybrids built during those three model years. For now, at least, Honda has sent out a letter to owners and is re-flashing the software in these vehicles – but that's not without its problems as well.

Honda has not revealed details of the changes to the software other than to note that it limits cycling of the battery. Some owners are claiming that the revised software has cut both performance and mileage, in some cases by up to 20 percent. While this is clearly making some drivers unhappy, it has also caught the attention of the California Air Resources Board (CARB) because the battery is considered to be part of the emissions control system.

According to CARB, more than four percent of Civics in the state have had batteries replaced which automatically triggers an investigation by the agency. Apparently no other hybrid has ever had such a high replacement rate. It's not at all uncommon for other hybrids to run well past 100,000 on the original battery and Ford Escape hybrids operating in New York taxi service have gone over 175,000 miles without battery problems. CARB is also concerned about the effect on the vehicle emissions if the hybrid system is shutting off the engine less frequently or using less electric boost. If CARB is not satisfied with Honda's response to the issue, the automaker could be forced to recall and replace the batteries or find another solution anyway.

As this is written, Honda has not yet responded to our request for more information on the root cause of the problem, or what sorts of changes are in the software update. We'll keep you in the loop if/when we hear back.

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