ZERO EMISSION VEHICLES AUSTRALIA
4-12 CELL LITHIUM BATTERY MANAGEMENT SYSTEM
If you need to disconnect the cell plug from the BMS, significant force is required for removal
as well. For easier removal, a flat blade screwdriver may be used to lever the positive end of
the plug out first, which should then be loose enough to remove by hand.
Ensure that all wiring is secured so it will not become damaged from vibration or abrasion.
Small fuses (~1A) may be used to protect wiring, best installed close to each cell terminal.
Device power is always taken from terminal
B+
. To provide power to the BMS, simply add
a short jumper wire from your most positive cell terminal to
B+
. (You can optionally run a
dedicated wire from battery positive to B+ to avoid voltage measurement errors on your most
positive cell, though it is usually only a few millivolts.) An example wiring diagram for 10
cells is shown below.
Relay outputs are floating / isolated, and have a maximum rating of 60V and 1A continuous.
In installations with a single “battery enable” relay, the LV and HV relays may be wired in
series such that either an over-voltage or under-voltage condition will open the relay to
isolate the battery pack as shown on the following page.
Once your wiring is complete, press the power button on the top left of the case, and the
status LED should come on. A green light indicates all cells are within correct voltage range,
and both relay outputs will be closed circuit. A steady red light indicates one or more cells
are over-voltage, and the HV Relay outputs will be open circuit. A blinking red light indicates
one or more cells are under-voltage, and the LV Relay outputs will be open circuit. Green/
red flashing indicates an over-temperature shutdown.
Protection Using a Single Contactor
It is possible for the BMS to control a single contactor
to protect against both under-voltage and over-voltage
conditions concurrently. To achieve this, the HV Relay and
LV Relay terminal pairs should be wired in series, as per
the diagram, right.
Note that in this configuration, if the BMS opens the
main contactor due to an under-voltage cell for example,
the battery pack will also be isolated from any charging
sources so will be unable to charge (and correct the under-
voltage condition) until the system is reset manually. For
this reason it is important in this case that BMS intervention is an exceptional circumstance,
and under normal operation chargers and loads will not cause any cells to exceed safe
range.
Current Shunt
The BMS12i may be supplied with either a 100A, 200A or 500A shunt. The shunt may
be installed at either the negative end, positive end, or even somewhere in the middle of
the battery pack. The shunt is connected via two wires to the associated terminals on the
BMS12i. For best performance, twisted pair wire is recommended. The sample wire from
the anode / positive side of the shunt (closest to the +ve terminal of the battery) should
be connected to the left-hand terminal (as shown on the wiring diagram, left). By default,
discharge amps are shown positive, though this can be reversed in settings if preferred. If
your polarity seems to be reversed (e.g discharge current is causing SoC to increase), simply
swap the two shunt wires at the BMS.
The BMS stores calibration for the shunt zero point in memory. If the current displayed is not
zero when it should be, you can hold a finger on the monitor to bring up Options buttons,
then tap Zero Current (while no current is flowing) to recalibrate the zero point.
Temperature Sensing
A temperature sensor may be connected to the BMS12i between the Temp and Ground
inputs. The scaling is calibrated for a 100Kohm NTC thermistor with B25/100 value of
4540K. These are available from us, or many large electronics vendors.
It is recommended that the temperature sensor is installed somewhere near the middle of the
pack, since this is typically the warmest location. Wires on the sensor may be extended as
3
4
