3 — APPLICATION-SPECIFIC FEATURES
Curtis 1239E-1269E Manual, os 37.0 RevA – May 2021
Return to TOC
pg. 28
BATTERY DISCHARGE INDICATOR
e battery discharge indicator (BDI) algorithm continuously calculates the battery state-of-charge
from the B+ voltage, whenever the main contactor is closed. e result of the BDI algorithm is the
variable BDI Percentage, which is viewable in the 1313/1314 menu Monitor » Battery. When KSI is
turned o, the present BDI Percentage is stored in nonvolatile memory.
The standard values for volts per cell are as follows, for flooded lead acid batteries and sealed
maintenance-free lead-acid batteries.
Battery Type
Flooded Sealed
Reset Volts Per Cell 2.09 2.09
Full Volts Per Cell 2.04 2.04
Empty Volts Per Cell 1.73 1.90
Use the standard values for the application’s type of batteries as the starting point in setting the reset,
full, and empty volts-per-cell parameters. Note: For non lead-acid batteries, including Lithium-Ion
battery packs, use the pack’s or cell manufacturer’s approved Battery Management System (BMS)
for determining BDI.
ISOLATION MONITOR
Isolating high voltage from the chassis reduces the risk of electric shock for technicians or operators
who, while grounded to the chassis, might touch a high voltage terminal or an ungrounded part with
an insulation failure. As long as the resistance to the vehicle chassis is large enough, the current that
results if a person touches a high voltage element will be limited to a safe level. A typical requirement
for the insulation resistance between live parts and the chassis is 1000 Ohms (Ω) multiplied by the
nominal voltage of the vehicle. It is also oen required to provide an onboard monitor that detects
insulation faults.
e 1239E/1269E controller has an internal circuit that measures the insulation resistance between
the high power circuit (high power battery positive and negative) and the vehicle chassis. is circuit
is enabled by setting the Insulation Resistance Fault reshold parameter to a value greater than zero.
When enabled, the circuit will be active aer the main contactor has closed. If Insulation Resistance
Fault reshold is set to zero, the isolation monitor is disabled and will open circuit its connection
between the high power circuit and the vehicle chassis. is path will also be disconnected in the
event of an Insulation Resistance Low Fault (fault code 76).
Unlike other isolation monitors, the Curtis 1239E/1269E isolation monitor will accurately measure
the insulation resistance of a fault regardless of its location. e fault can be from chassis to B+, B
–,
the midpoint of the battery pack (or any other point), any motor connection (including the star
connection of a wye-wound motor), etc. While the isolation monitor is enabled, there will be a
periodic connection of about 380 kΩ (minimum) between the high power circuit and the chassis. e
lowest possible resistance between the high power circuit and the chassis is the parallel combination
of the isolation monitor resistance and the fault resistance. For example, if the minimum worst-case
leakage path desired is 190 kΩ, the Insulation Resistance Fault reshold should be set to 380 kΩ.
Note that the 12V low power circuit ground must be connected to the vehicle chassis for the isolation
monitor to function properly. Also note that only one isolation monitor should be enabled on a given
vehicle. e accuracy of the Curtis 1239E/1269E insulation resistance measurement is ±10% of full
scale, from 6 kΩ to 500 kΩ.
To Next Page
Loading...
