Reverse Battery Polarity Warning - National Instruments NI DIDS-2103 User Manual

2.1 REVERSE BATTERY POLARITY WARNING

NI Powertrain Controls power modules are not internally protected against reverse battery polarity.
Do not reverse the battery polarity or damage will occur. This event is not covered under warranty.
All NI Powertrain Controls modules with a 10-pin screw terminal block have identical external
power and ground connections. Please take necessary precautions to ensure that BATT (0)
and GND (9) are not connected in reverse polarity. The BATT (0) terminal will accept positive
7-32VDC with respect to the GND (9) terminal. Please refer to the user manual for details.
To provide system-level protection against reverse battery polarity, implement the following simple external
main-power-relay circuit:
Figure 2.1.a, Reverse Battery Protection Diagram
Notes:
1.) The relay shown is a type of automotive relay which includes an internal series diode with terminal 85. This diode
will prevent reverse battery from energizing the relay.
2.) Terminals 30 and 87 are screw terminals and should be connected with soldered ring terminals.
3.) Terminals 85 and 86 are 0.250 X 0.031 inch (6.3 X 0.8 mm) push-on terminals.
4.) A fuse is recommended between the battery and relay.
5.) An optional switch may be placed in series with relay terminal 86.
6.) Simply placing a high-current-capacity diode in series with the system power is not an acceptable method
of reverse battery protection because it will not allow the NI Powertrain Controls modules to perform current
recirculation while switching inductive loads.
7.) The relay is currently available from www.ni.com.
6 | ni.com | NI DIDS-2100 Series User Manual