Posted by Elmo P. Shagnasty on July 14, 2007, 3:10 pm
The battery fails or it doesn't fail.
It doesn't have prescribed replacement interval.
And failure is objective, not subjective.
Do you go and replace things that haven't failed?
Posted by News on July 14, 2007, 3:15 pm
Elmo P. Shagnasty wrote:
The allusion was to (irrespective of the published MTBF, which you
suggest is "not in the car's lifetime" or "never") your own personal
version of MTBF, a.k.a. "when and if it fails".
This is moswt often longer or shorter than the stated or theoretical MTBF.
Posted by on July 15, 2007, 7:38 am
There's a MTBF? Last I knew, Toyota said expect the batteries to retain 98%
of their charging capacity at 200,000 miles.
Normally the batteries aren't allowed to charge or discharge anywhere near
full capacity and it's for this reason they last.
Posted by bob on July 19, 2007, 2:46 am
very dumb elmo. batteries have predictable lives.
Posted by Ike on July 19, 2007, 4:21 am
When a common cell is run until depletion, its life is
predictable based upon known capacity, expressed in ampere-hours
as a function of stored chemical energy.
No one has presented a reliable algorithm to predict the life of
cells that are (1) operated between some non-peak charge state
and some non-minimum discharge state, (2) charged by a highly
optimized method that nonetheless varies based on operating
conditions, (3) operated in many different environmental
conditions, (4) operated with unpredictable demands, and (5)
used over an unpredictable time schedule. In this case, the
battery (a battery is comprised of multiple cells) consists of
more than 100 nickel metal hydride cells in series, and the
failure of any one of them kills the entire series system. That
further complicates the equation because there is no graceful
In short, for these batteries it may be possible to make vague
predictions of nominal life under nominal conditions, but it
will be a very, very flat bellcurve with huge variability.