True battery SOC (State of Charge) goes from 0% (totally drained) to 100%
(totally stuffed). However, like in real life, being totally drained or stuffed is
usually stressful, even damaging. So, in designing a battery power system,
the bottom 5% or more, and the top 5% or more are engineered to be forbidden
(possible or likely damage) zones, leaving an "available" capacity of 90% or less.
Not wanting to confuse owners and drivers with the facts, the car often reports
this available energy or capacity as 0 to 100, like fullness of a gas tank.
However, many USA drivers are accustomed to reading Empty as "down to the reserve",
and not "the car is now stopping". So, another "state of fullness" number is usually
actually shown on the dash as something like a "fuel gauge", going from 0 to 100 or
Empty to Full, but so far the EVs tend to not indicate the "below empty" range, like
some traditional gas gauges do (the indicator needle moving below E).
There is one further significant complication. A typical gas tank does not change
in size, so tank fullness also indicates the quantity of fuel. However, with typical
EV battery pack systems, the capacity of the pack can decrease over time, so that
the "Full" condition gradually represents less available fuel, thus a decreasing range.
GIDs, found in the LEAF, appears to be a value that represents the amount of usable
energy or fuel, and most of the SOC-derived numbers are just tank/battery fullness
numbers designed to make the driver/owner feel better.
That said, all of these numbers are estimates, and these estimates are subject to
re-calculation at any time, as conditions permit or require, like as temperature
changes, or the cells in the pack get near empty, or near full.
Yes, it is a slightly new, but facinating, ballgame.
Last edited by garygid
on Sun May 18, 2014 7:57 am, edited 2 times in total.
See SOC/GID-Meter and CAN-Do Info
2011 LEAF, 2014 Tesla S85
2018 & 2019 Tesla Model 3
Solar PV: 33 x 225W -> 7 kW max AC
Craigslist: Xm5000Li Electric Motorcycle