A Battery Management System (BMS) is responsible for monitoring the health of battery cells by measuring temperature and detecting current leaks or overcurrent conditions. Additionally, the BMS manages voltage levels in individual cells such that energy from discharging, charging, or recovered from regenerative breaking is distributed or sourced evenly to prolong system lifespan.
Current Sensing:
It’s important for the current sensing amplifier to be able to monitor current quickly and detect leakage/overcurrent as it occurs. For this a faster transient response is required from amplifiers with a high slew rate and wide bandwidth.
Table 1: Amplifier recommendations for current sensing OPA388-Q1 OPA320-Q1 OPA322-Q1
|
Number of |
Vs min |
Vs max |
GBW typ |
Slew Rate |
Vos max |
|
|
OPAx388-Q1 |
1,2 |
1.8 |
5.5 |
10 |
5 |
0.005 |
|
1,2 |
1.8 |
5.5 |
20 |
10 |
0.15 |
|
|
OPAx322-Q1 |
1,2,4 |
1.8 |
5.5 |
20 |
10 |
2 |
High Voltage Diagnostics:
As the name implies the HV Diagnostics socket requires a high voltage component to measure both voltage and current. The amplifier should also have a wide bandwidth and minimize offset/noise.
Table 2: Amplifier recommendations for high voltage diagnostics OPA192-Q1 OPA197-Q1 TLV197-Q1
|
Number of |
Vs min |
Vs max |
Vos max |
Drift typ |
Vn typ |
|
|
1,2 |
4.5 |
36 |
0.025 |
0.1 |
5.5 |
|
|
1,2,4 |
4.5 |
36 |
0.25 |
.5 |
5.5 |
|
|
TLVx197-Q1 |
1,2,4 |
4.5 |
36 |
0.5 |
1 |
5.5 |
Cell Supervision:
Battery monitoring via cell supervision is necessary for monitoring the balanced distribution of energy among cells and for current faults and leakage. Unlike the current sensing socket here accurate measurements with low offset voltage and drift take priority over speed with no bandwidth requirements.
Table 3: Amplifier recommendations for cell supervision OPA180-Q1 OPA333-Q1 OPA317-Q1
|
Number of |
Vs min |
Vs max |
Vos max |
Drift typ |
IBias typ |
Vn typ |
|
|
1,2 |
1.8 |
5.5 |
0.075 |
0.1 |
250 |
10 |
|
|
1,2 |
1.8 |
5.5 |
0.01 |
0.02 |
70 |
55 |
|
|
OPAx317-Q1 |
1,2 |
1.8 |
5.5 |
0.09 |
0.05 |
200 |
55 |
Temperature Sensing:
Because temperature is not constant throughout the entire system safe designs will include multiple amplifiers connecting thermistors to an ADC or MCU. To address settling issues the ADC-driving amplifier should have low drift over temperature.
Table 4: Amplifier recommendations for cell temperature sensing
|
Number of |
Vs min |
Vs max |
Vos max |
Drift typ |
IBias typ |
Vn typ |
|
|
1,2,4 |
2.2 |
5.5 |
0.025 |
0.32 |
0.2 |
7.5 |
|
|
1,2 |
1.8 |
5.5 |
0.01 |
0.02 |
70 |
55 |
|
|
OPAx317-Q1 |
1,2 |
1.8 |
5.5 |
0.09 |
0.05 |
200 |
55 |
High Voltage Safety Interlock:
Safety Interlock components should be as accurate as possible in their monitoring, Zero-Drift or low-drift components are ideal here. Ideally non-chopper, low-drift amplifiers such as the OPA376-Q1 would be used here as choppers are prone to glitches caused by uneven spikes in the input bias current. This phenomenon can be addressed, however, by matching impedances.
Table 5: Amplifier recommendations for high voltage safety interlock
|
Number of |
Vs min |
Vs max |
Vos max |
Drift typ |
Vn |
|
|
1,2 |
1.8 |
5.5 |
0.01 |
0.02 |
70 |
|
|
1,2,4 |
2.2 |
5.5 |
0.025 |
0.32 |
7.5 |
|
|
OPAx377-Q1 |
1,2,4 |
2.2 |
5.5 |
1 |
0.32 |
7.5 |
For useful resources and additional information, please make sure to check out the following content:
HEV/EV battery management systems explained simply (Technical Article)
Voltage and current sensing in HEV/EV applications (Technical Article)
Understanding current sensing in HEV/EV batteries (Technical Article)
Battery management system (BMS) (Reference Design)
TI Battery Management Video Series (Video Series)
BMS EE Slides (End Equipment Slides)
