Orion Jr. BMS Manual
–
Rev. 2
22
A sample schematic for connecting the open drain outputs with an opto-isolator (resistor values must be calculated based on voltage and opto-
isolator requirements). Note: For Rev A units, the maximum switching voltage is 24V.
If the signals will be used to drive relays with coils larger than 175mA, contactors, or other loads, an
amplification method must be used so that the BMS does not sink more than the maximum allowable
current. A common method for this is to use a MOSFET to amplify the signal to provide power to a
larger relay or contactor. A schematic is shown below for this method.
Schematic showing a P-channel MOSFET used to amplify the open drain output. Note: For Rev A units, the maximum switching voltage is
24V.
Another method is to use a smaller relay to turn on power for the larger relay/contactor. A schematic for
this is shown below.
Orion Jr. BMS Manual
–
Rev. 2
23
Checking open drain outputs
Open drain outputs will read zero volts on a voltmeter whether or not they are on since they sink current
rather than source it. A simple method for testing the outputs is to connect an LED or small light bulb
(under 100mA) between the output pin and +12v (or any voltage between 5V and 24V for Rev A and 48
V for Rev B.) If an LED is used, a series resistor (often between 330 ohm and 1k ohm) must be used to
limit current through the diode. When the output is on, the LED or bulb will illuminate. A schematic for
this is pictured below.
Wiring the multipurpose input
The multipurpose input has a user selectable function and can be used for functions such as clearing
fault codes or indicating a certain status to the BMS. This input is present only on Rev. B & C units. A
voltage of 9
–
60V may be applied to this pin to indicate an “on” status. The voltage of this pin may not
exceed 60V at any point and a voltage below 9V may cause the status of this pin to become undefined.
The voltage source used to generate the signal for this pin must be fused at the source with a fuse no
larger than 3A. Since this input has a current draw of only a few mA, a significantly smaller fuse may be
used if the fuse is not shared with other circuits. Fuses must be rated for the full DC working voltage
and have a suitable interrupting current rating for the application.
Wiring the analog 0-5V outputs
The Orion Jr. is equipped with three analog 0 to 5V voltage outputs designed to aid in integrating the
Orion Jr. with non-digital applications including voltage based displays. The outputs include pack state
of charge, charge current limit, and discharge current limit.
Each of the 0-5V analog voltage outputs can provide or sink up to 10mA of current. If more current is
necessary or if a different voltage range is necessary, an external analog buffer or op-amp must be
used to amplify the signal. The analog voltages are generated inside the Orion Jr. unit by a digital-to-
analog converter.
State of charge output (pin 11) - This output provides the calculated state of charge. 0V corresponds
to 0% state of charge and 5V corresponds to 100% state of charge. This output often is used to display
state of charge in applications where digital communications are not available.
Charge current limit (pin 13) - This output provides an analog representation of the maximum current
that the battery can accept at any given time. 0V corresponds to 0 amps and 5V corresponds to the
maximum amperage set in the profile for this specific output. Please see the software manual for
information on setting this maximum value.
Orion Jr. BMS Manual
–
Rev. 2
24
While this output can be reliably used to limit current, it should be used in conjunction with the charge
enable signal output (pin 10) which provides an analog watchdog shutoff circuit. Although unlikely, it is
possible for the digital-to-analog converter to fail, leaving the voltage in an undefined state.
Discharge current limit (pin 14) - This output provides an analog representation of the maximum
current that the battery can discharge at any given time. 0V corresponds to 0 amps and 5V
corresponds to the maximum amperage set in the profile for this specific output. Please see the
software manual for information on setting this maximum value.
While this output can be reliably used to limit current, it should be used in conjunction with the
discharge enable signal output (pin 3) which provides an analog watchdog shutoff circuit. Although
unlikely, it is possible for the digital-to-analog converter to fail, leaving the voltage in an undefined state.
Thermistors (Pins 10, 12, 16, and 8)
The Orion Jr. main unit can have up to two (revision A & B) or three (revision C) thermistors directly
connected to the unit. These thermistors are designed to provide the BMS with a representative idea of
the pack temperature. The thermistors should be spread throughout the battery pack in a manner which
provides the most representative temperatures possible. If the battery pack is split into multiple physical
locations, at least one thermistor should be placed in each physical location. If the battery pack is in
one physical location, sensors should be scattered through different areas of the pack such as the
middle and outer portions of the pack.
Some applications may require the measurement of each individual cell temperature while
representative temperature readings are suitable for others. It is the integrator’s responsibility to
determine the necessary number of temperature monitors. If monitoring more temperatures is
necessary, an external thermistor expansion module is available which can monitor up to 80 additional
thermistors.
The thermistors are 10K NTC thermistors with a B25/50 value of 3380K. Other B values can be used
through the use of an external thermistor expansion module. Custom configurations of the main Orion
Jr. unit for B values may be available for high volume applications requiring a different B value. One
end of the thermistor is connected to the appropriate thermistor pin and the other is grounded to the
thermistor ground pin. As thermistors are resistive, polarity does not matter.
Thermistors can be attached to the battery cells in different ways depending on the type of cell. The
thermistors sold with the Orion Jr. have epoxy coated beads at the ends. They can be taped or glued to
cells. Some thermistors are attached to ring terminals and can be screwed onto battery terminals. Care
must be taken if the thermistors are attached to ring terminals to ensure that they have
sufficient electrical isolation from the battery pack.
The thermistor measurement pins are NOT
electrically isolated from any other pin on the Main I/O connector, and a breakdown in isolation
may cause a short!
Insufficient isolation can cause shorts outside the BMS and/or catastrophic
damage to the BMS unit. Fuses to guard against shorts on the thermistors may be necessary in certain
applications.