I heard that there is a lump sum of $5000-6000 to replace the battery
in hybrid vehicles sometime after 40,000 miles.  Supposedly most of
this charge is disposal, and this is becoming an environmental issue. 
Is this true??  Does this apply to all hybrid models?

Both Toyota and Honda have extended warranties (compared to the
bumper-to-bumper) on their battery packs of at least 8 yrs/80000
miles.  Can't say for sure about Ford.  Last I heard replacement would
run about $3000 although this is expected to come down as more hybrids
get on the road.

I heard the Prius batteries last over 150,000 miles (and in
California, they are warrantied at that).  I also heard that a new
battery pack TODAY would run about $3500.  That price is expected to
come down in the future.  (It used to be $10,000 several years ago.)

J.

My concern has always been the unit that turns gasoline into electric power.

A bad tank of gas with water, rust, paint chips, lead, etcetra seems
an easy way to foul things up.

________________________________ also

Battery pack failure mechanisms used to be crystals of lead that broke
through the insulating plates between cells and a sludge like material
that dropped to the bottom of the cells.  Both would cause shorts. 
Perhaps the battery technology has advanced.

I was quite a skeptic of hybrid battery life when they first came out,
but now I'm trusting them more.  My change of heart is mostly due to
the lack of dead batteries so far and they've been around 6 years.  My
origional estimate was about 6 year average lifespan... so apparently
I was off by atleast several years.

Since the batery charges itself as the car is running, I don't think
milage is an issue for when it will die... the age is much more
important.  If you drive 300,000 miles is 3 years, I seriously doubt
the battery will be dead yet.  But if you drive 100,000 miles in 15
years, I have little doubt the battery will have to be replace before
then.

The cost is muche less than it once was to replace the battery.  That
was also a major concern of mine when they first came out.  The price
has dropped from around $6,000 to $3,000 and I think it's still
falling slowly.

The real hidden cost of the hybrid is performance.  The battery weighs
between 700 and 1200 lbs, add that to a 2000 lb ECHO (to make a Prius)
or even a heavy SUV and your performance suffers tremendously.  Don't
only look at horsepower, look at horsepower and weight and you'll see
that high mpg hybrids are very weak.

I suspect the all electric cars have disappeared from the market
because the companies saw large warenty cost battery replacements on
the horizon. The hybred design protects the battery from abuse by the
owner at some loss of reliability, flexibility, gas milage and
performance. The lead acid battery will likely continue to become less
costly (adjusted for inflation) But new battery types will likely be
very costly to replace. Buyers should carefully read the fine print in
their battery warrenty, before making the purchase. Don't buy, if you
will be tempted to modify the vehical for improved purformance.
Dealers may be reluctant to replace marginal batteries, and the
vehical will resell for only a few hundred dollars after the warrenty
has expired, even if the 0 to 75 mph time is still less than twice the
new performance time.    Neil

Disposal of any battery is hazardous but the major issue here would be
how often do the batteries get discharged enough to be disposed.
The car manufactures give a warranty of 8 years/80000 miles for the
battery. But this is very vague as the battery life depends on how
much a person drives the vehicle. The battery gets charged while
decelerating/the fuel charges the battery (depending on the type of
HEV).
At the same time, the cost of a battery has reduced to somewhere about
$2500-$3500 and is expected to fall further. Moreover, with Li-Ion
batteries coming into fore, the performance of batteries will improve.
The main issue of weight of batteries detrimenting the performance of
the HEV will also lessen with this.

There are also plans of imposing laws which will enable safer and
better collection of batteries which will then be recycled for use
once again. These batteries will include NiMh, NiCd and Li batteries
as well.