Battery Analysis and Care (BACS) Battery Monitoring System

BACS is an advanced, 3rd generation battery management system.

Generex BACS BMS Connection Diagram

The system comprises of 4 main parts

Battery Monitoring and Equalisation

BACS battery monitoring module

A module is connected to each battery. It monitors for temperature and impedance, while actively adjusting the battery voltage to ensure the voltage is set at the UPS charger level. This process is called equalisation.

When actively monitoring and equalising batteries yields the following benefits

  • Avoiding over charging
  • Avoiding under charging
  • Avoiding sulfation
  • Detecting stratification
  • Detecting problems with the battery by monitoring temperature and impedance
  • Detecting and alerting to thermal runaway
  • increases battery life by 30%

Batteries supported

  • 12V: 7-600Ah lead batteries
    Measuring value: 9.7V-17V
    RI range: 0.5-60mOhm
    150mA Equalizing
  • 16V: 7-600Ah lead batteries
    Measuring value: 9.7V-21V
    RI range: 0.5-60mOhm
    150mA Equalizing
  • 6V: 7-900Ah batteries
    Measuring value: 4.8V-8V
    RI range: 0.5-60mOhm
    300mA Equalizing
  • 2V: 7-9000Ah batteries
    RI range: 0.02-6mOhm
    850mA Equalizing

NiCd, NiMH, flooded and VRLA lead batteries

Monitoring and Reporting

BACS System status featuring battery string and number, voltage, temperature, impedance and equalisation

The BACS® WEB-MANAGER acts as the battery system‘s central control unit. It gathers, evaluates, and stores system information. The user is provided access to three web server pages. One displays the actual status of batteries; a second shows actual UPS data; the third shows environmental data and alarm contacts status. The web browser interface of the system is designed for easy configuration. It provides the user with access to all system values and events. A flexible programming interface known as the EVENT MANAGER coordinates a system response to significant events (alarms, notifications, etc.).

The WEB-MANAGER handles events involving the UPS, inverters, environmental sensors, transfer switches, generators, dry contacts, and other devices.


BACS® includes a full qualified UPS/SNMP and MODBUS manager, one that is compatible with any UPS presently on the market! Among BMS systems on the market, this function is unique.


BACS® allows MODBUS clients to read the system data through IP and RS232 (and, optionally, RS485), as well as through SNMP. Conversion to PROFBIS and LONBUS is possible through optional converters.


Provides graphical BACS® data analysis and reporting.

BACS View software stores battery voltage, impedance, temperature and discharge logs

Alerting and Warning System

BACS® has the ability to send out ―advance warning alarms via email, email-to-SMS, network message, SNMP, RCCMD, MODBUS, and, optionally, PROFIBUS, LONBUS, and GSM. (Alarm parameters can be configured by the user to match battery type.)

For instance, discovering rising internal resistance in a battery—an indicator of corrosion or sulfation— BACS® triggers an alarm.

Given early warning of issues, the user is able to investigate and take action far in advance of the consequences that can result from them. The effects of corrective actions taken are immediately observable. In addition to internal resistance, BACS® monitors voltage, temperature, the equalising process, the system‘s charging/discharging cycles, and, optionally, current. When pre-set thresholds of these categories are crossed, an alarm is communicated.

In addition to sending network alarms, BACS® also warns users via audible and visual signals (a buzzer on the BACS® MANAGER and alarm LEDs on the module and BACS® MANAGER).

UPS integration

BACS® has the ability to integrate UPS monitoring and alerting via the serial port. Over 1400 UPS manufacturers are supported.

BACS battery management system (BMS) supports uninterruptible power supply (UPS) integration for monitoring, logging and alerts

Specifications and Standards

BACS® system

BACS Webmanager BMS Controller
ARM Cortex A8 800MHz processor
512 MB storage for battery history
Stabilized external power supply 12V 2000mA
3x RS-232 interfaces, (COM1=UPS/power device, COM2=Multipurpose, service port for Windows BACS READER and PROGRAMMER software)
2x battery bus converter outputs internal
1x RJ45, 10/100Mbit Ethernet
1x potential-free contact (2 pole screw terminal for max. 1.0mm², rated load 24 VDC /1A)
3x LED (Manager status, UPS/device alarm, BACS alarm)
1x buzzer with mute button
Aluminium, RAL 7035 (light gray) ETL listed, FCC class A
130 x125 x 30mm (W x L x H)
Operating conditions
Temperature 0-60°C, max. humidity 20-95%, not condensing
MTBF (Calculated)
849,192 hours; 96.9 years

BACS® modules (rev 3)

BACS Battery Module
Measuring modules with equalisation
BACS® patent no.: DE 102004013351.4
Power consumption from battery
Consumption at normal operation: 15-20mA Consumption at “Sleep Mode” < 1mA
Measuring precision
Internal resistance : < 10 % at C40, < 5% at C20/30 Voltage : < 0.5 % Temperature: < 15 %
2x RJ10 for BACS battery bus Internal RS232 bus interface 1x button for the addressing Temperature sensor -35 to + 85 °C Optical display LED (alarms red/green, mode red/green)
ABS housing (UL certified, flame retardant, cooling fins)
55 x 80 x 24 mm (B x H x T), 45g
Operating conditions
Temperature 0 - 60°C, max. humidity 90%, not condensing IP 42 coated against dust and condensate)
High Voltage Tested
Protection against high ohmic batteries fault voltages up to 150 Volt /per module (fuse opens). At higher voltages the fuse opens, but BACS module is damaged. All REV 3.1 modules are designed for fault voltages up to 600 Volt
MTBF (calculated)
87,600 hours (10 years)

Models and Specifications

BACS Module C20
Module BACS® C20
REV 3 module for 12 Volt 7-600Ah lead batteries (UL certified)
Voltage Range
9.7V – 17V
RI Range
Equalisation Current
0.15 A
BACS Module C23
Module BACS® C23
REV 3 module for 16 Volt 7-600Ah lead batteries (UL certified)
Voltage Range
9.7V – 21V
RI Range
Equalisation Current
0.12 A
BACS Module C30
Module BACS® C30
REV 3 module for 6 Volt 7-900Ah lead batteries (UL certified)
Voltage Range
4.8V – 8V
RI Range
Equalisation Current
0.3 A
BACS Module C40
Module BACS® C40
REV 3 module for 2 Volt 7-5000Ah lead batteries, NiCd, NiMH batteries (UL certified)
Voltage Range
1.25V – 3.2V
RI Range
Equalisation Current
0.9 A (at 2.27V)

Options and Accessories

Current Sensors

BACS CS Current Transformer (CT)

BACS® DC current sensor 50/200/400/1000/2000 Ampere

Ord. No: BACS_CSH50, BACS_CSH200, BACS_CSH400, BACS_CSH1000, BACS_CSH2000 +/-50A, +/-200A, +/-400A, +/-1000A, +/-2000A DC Current transducer diameter hole : 21mm (BACS_CSH50) /40 mm

DC current sensor for measuring battery string discharge and charging process
BACS® patent no.: DE 102004013351.4
Power supply
Consumption at normal operation: 15-20mA Consumption at “Sleep Mode” < 1mA
Power consumption
2x RJ10 for BACS battery bus cable, pluggable system
DIN rail
Dimension, weight
110 x 82 x 125 mm (LxWxH), 420g
Operating condition
Temperature 0 - 60°C, max. humidity 90%, not condensated

BACS bus interface GX_R_AUX

BACS® bus interface GX_R_AUX

Ord. No: GX_R_AUX
BACS bus module with free programmable 4 digital inputs and 4 relay outputs.
A typical application is the control of a battery breaker in case of ― thermal runaway alarm in the battery system. (According to US Norm International Fire Code IFC 608.3 the batteries of a UPS have to be isolatied in case of a thermal runaway). In case of a high battery temperature and increasing voltages during float charge, the GX_R_AUX may open the battery breaker to stop a further increase of the temperatures in the batteries. Individual programming of the relays through web interface.

Power supply
No external power supply, device is powered by the BACS bus
Power consumption
approx. 170mA
4 potential-free relays, 4 digital inputs
Polyamid, pluggable system DIN rail
Dimension, weight
75 x 75 x 45mm (LxWxH), 170g
Operating condition
Temperature 0 - 60°C, max. humidity 90%, not condensated

Generex SensorManager

Sensor Manager II

Used for adding additional sensors


Generex Battery Management Datasheet
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