[ausev] Foxxy Lady is on the road!

[Brian Lasseter]

On Wed, Nov 19, 2008 at 12:03 PM, Willie McKemie <mckemie at spamcop.net> wrote:
> It is my understanding that you are damaging or risking damage to your
> batteries if you allow the voltage to drop to 1.75 v/cell (~85 volts
> on a 96 volt pack).  Can the Zilla be set to cut off if it sees less
> than, say, 87 volts?

The Zilla has a "Low Battery Voltage Indicator Voltage" (where it
turns on a light) and a "Low Battery Voltage"... The Zilla will not
run the batteries beyond "Low Battery Voltage", it will just lower the
current draw to maintain the traction pack above the "Low Battery
Voltage".   It's cool like that.

However when talking about State of Charge (SOC), you have to remember
that the measurements are only valid when the battery pack is not
under load.  The voltage will drop as the current increases.

So 1.75V per cell implies that the cell is "dead" (0% SOC), but that's
only if the cell is not having current drawn from it.  So if you are
at a stop light, and see 1.75V per cell... then you are in trouble.
If you are driving down the street and you see 1.75V per cell, that is
not a problem (yet).

Take my 144V pack for instance.  I usually see 155V (or 2.15V per
cell) before I back out of the garage with a full battery.  Once I get
below 30% state of charge, I routinely see the pack voltage dip to
110V (or 1.5V per cell) as I accelerate, however even on the occasion
when my Xantrex Battery meter said I had "3% SOC", I still saw over
130V (or 1.8V per cell) once I finished getting back into my garage
with my pack.


I have my "Low Battery Voltage Indicator Voltage" (LBVI) set at 110V
or 1.5V per cell, and my "Low Battery Voltate" (LBV) set at 90V or
1.25V per cell in my Zilla.


-- 
TTFN,
Brian "Lasso" Lasseter

"No Sane man will dance."   -Cicero (106-43 B.C.)