Nissan Leaf Battery Warranty Same as Chevy Volt's - 8 Years or 100,000 Miles

The released facts as I understand them are that the battery is good for around 1,000 cycles down to 80% if normally charged at level I or II and to 70% if charged several times a day on level III.
Taking part charges as additively equivalent to full charges, then on the slow charge routine the car should travel the average between 80% and 100% of it's range, 90%, so would be good for 90,000 miles based on a 100 mile range.
However this does not allow for a/c, heating etc, so the real range might on conservative assumptions appropriate for guarantee purposes be 80 miles when new.
So 90% of the 80 mile times 1,000 gives you about 72,000 miles down to 80% battery capacity.

Running the figures in the same way for the fast charge scenario, which for guarantee purposes is the most relevant, you come out to 68,000 miles. (Average of 70% and 100% = 85%, with nominal maximum range of 80,000 miles)

So I think that Nissan were hoping to guarantee the battery for 60,000 miles to cover a worst case scenario, although it should be noted that this is not strictly worst case, which would use around 50 miles as nominal range from new to cover always driving in adverse conditions, and with fast charging come out to 42,500 miles.

However, in normal use things are not so bad. Not many people are likely to almost always fast charge - indeed, that would be difficult to do for some years, as there aren't the chargers available.

In addition, for most chemistries at least part-depleting the battery and topping it off greatly increases the battery life, I understand, by up to 5-6 times nominal.
So most folk should get way over 100,000 miles from their batteries, as they normally run about 30 miles or so a day and top it up on slow charge at home.

If these calculations are right it does mean that Nissan is in a bit of a fix for guarantees though, as they shot for a battery good for 1,000 charges, and they really need at least the 1,500 of the Kokam batteries to be confident in issuing long guarantees.
Coming close to the Volt battery guarantee will be difficult, and even 80,000 miles will be difficult and involve accepting a certain amount of losses from the depletion curves Nissan have issued

From what they have told us, before 100k a fair number of batteries which have had hard use will need changing, so they are prepared to take that on the chin.
Most should be just fine though, for way over 100k if they are charged at home on a top-up basis.

I ran these figures a couple of days ago, so the news that Nissan is going for 100k miles seems to me to mean that Nissan have probably accepted a small return rate under guarantee to give the high mileage warranty for hard used batteries.
Additionally, they may figure that they can reduce costs enough by the time that the guarantees are due that it will not cost them much, and may be planning on tweaking the battery chemistry by the time when volumes climb to significant levels, say in the hundreds of thousands of sales a year.

Most people who charge at home on a usually only partially depleted battery should be good if my estimates of linger life are accurate for part charging for way over 100k anyway, perhaps 200 or even 300k.

I keep hearing that the LG Chem / Compact Power battery chemistry chosen by both GM and Ford for their EVs is superior in terms of the number of charge cycles it's good for. If this is believed to be the case, it would be great if someone can share facts and/or theories to back this up. I paid $99 to reserve a LEAF, but might hold out for the Ford Focus EV if its battery life is believed to be that much better. I'd like to be able to hang on to whichever car I purchase for 10 years, or possibly much longer, since EVs have fewer parts to service. As a Californian, I might have to make a decision relatively soon. Thanks in advance to anyone who has information to share!

I can't find conclusive information on the life of the LG Chem batteries in BEVs - they use different ones to those in a HEV.
There is also an opaque relationship between LG Chem and SK Energy, both South Korean companies, which to some degree at least co-operate in development.
Hyundai started off using LG Chem batteries but seems to have switched to SK Energy.
That may be simply switching labels in the factory for all I know though.

All of which is a complicated way of saying that I don't know, and AFAIK the information is not out there to tell.
What is clear though is that the Ford seems to be loosing most of it's boot space to batteries:
http://www.youtube.com/watch?v=tb4gGXomNz4&feature=related

As a Californian you will be eligible for the extra $5k from the state, and the battery is guaranteed on the Leaf for 8 years or 100,000 miles, so what's not to like?
By the time you need to replace your battery prices should have dropped substantially, or you could go to town and buy a more powerful pack so as to double your range to around 200 miles nominal.
Nissan/AESC have designed a battery with double the power for production in around 2014-5, plenty of time before you are likely to need to change yours.
With the condition of public finances, who is to say whether the $5k Californian rebate will still be available by the time the Ford is, and that is a substantial chunk of any replacement costs.
If you are still worried you could always lease the Leaf at a very reasonable rate, but with their very good guarantee I can't see the point.
As an early adopter you may also be eligible for the free charger - I don't know the details.
You can always hang on for a better deal, but with the Government throwing money at you it seems unwise to do so.

@davemart1: Thank you for the response. Even if the Ford Focus EV does end up with better batteries, the LEAF's interior as a whole does seem significantly roomier, which is important to a family of four like ours. Nissan's just-announced warranty is very comforting, though it seems likely (based on the recent survey) that battery capacity degradation of probably 30% at the end of eight years would be considered "acceptable". That is definitely less than ideal, but we don't live in an ideal world, and you are right about the unpredictable nature of future public subsidies. Most likely, we will purchase the LEAF when it's available to us, of course keeping our eyes and ears open in the meantime.

I'm not usually an early adopter, but to me this is different. I want to be able to provide my family (and ultimately our nation) the security of not directly relying on world oil markets, which could get really crazy in the event of a Middle East war. And I also like the environmental benefits of EVs, particularly in a smog-prone state like CA with a greater share of "clean" electricity supply. Ultimately, my goal is to install rooftop solar to power both the car and our home, thus insulating us from electricity price increases while providing additional environmental benefits.

asbasile,
From the information that Nissan have given the drop after 100k only hits 30% if you are charging regularly using a Level III charger - IOW you are using it repeatedly for long distance travel and charging outside the home in 30 minutes.
Although their warranty may only be for that, if you normally charge at home you should be just fine for the 100k down to 80%, and if fast charging degrades the battery about twice as fast, as Toshiba, for instance, say is true for theirs you should be good for around 150k miles or even 200k before you hit 70%, depending on the depletion curve characteristics.