Batscan is a battery monitoring system built as a modular data acquisition system where a PC computer evaluates and stores the data collected from decentralized measuring devices (modules) containing analog to digital converters.
A RS485 serial bus network provides the communication link between the PC and all connected modules. The bus also supplies power to the modules.
Safety issues
A battery has normally only two connection points, the + and – terminals, in a large UPS battery there is one thick cable connected to each terminal. These cables can carry a very high current and the voltage is often several hundred volts, it is therefore very important to protect the cables from mechanical stress and ware to avoid any risk for a short circuit. The cables must also be well isolated for human protection. This is not a very big problem with only two cables between the battery and the UPS.
However, if a battery monitoring system is installed the number of connections required to the battery can increase to several hundred. Each of them adding a potential risk for battery discharge, short circuit and human injury.
Batscan recognizes this as the most critical safety issue with any battery monitoring system and uses several combined methods to address this particular problem.
High Voltage Isolation Transformers
The voltage measuring modules are internally isolated with a high voltage transformer that separates the digital side connected to the communication bus from the analogue side connected to the hazardous battery voltage.
Current Limiting Resistors
All connections to the battery cells to be monitored are made trough protective high ohmic resistors. These resistors provide the primary protection barrier between the monitoring system and the battery.
By using resistors instead of fuses maximum worst case current is limited to a safe value under all conditions.
For example; Even if the measuring wire from the +terminal of the first cell accidentally is shortened directly to the -terminal of the last cell in a 500 Volt battery, the current through the protective resistor cannot exceed 250µA (0.000250 A) with a maximum heat dissipation of 0.125W.
Under normal, no fault, condition the maximum current drawn from the battery is less than 30µA (0.000030 A).
Separate power supply
All measuring modules are powered from the communication network and do not rely on the monitored battery for its operation. This also preserves the battery’s integrity.
Observe Without Affecting
Batscan is a true monitoring system intended only to observe the battery, without any means of affecting it in any way, not even in the event of a fault condition in the monitoring system itself.
This means that Batscan can not inject any current, AC or DC, into the battery, nor will it attempt to send any commands to the UPS to initiate a test procedure.
However, Batscan is fully compatible with any automated scheme for battery tests initiated by other components in the power system, including periodic discharges or reduction of charge voltage used by some UPS’s for determining battery condition.
No missing data
Since Batscan continuously monitors all parameters of the battery at full speed, the results from any power outage or battery test – whether automatically or manually initiated, will always be recorded at maximum resolution by the PC.
For each complete measuring cycle, which is typically repeated every 5 seconds, all individual channels are measured simultaneously and their new value are compared to the last value saved by the PC if the difference exceeds a predefined minimum-change-to-save-threshold the new value will be saved together with a timestamp.
All measured values are also compared to predefined low and high alarm thresholds, when all channels measures within their respective limits a normally open (NO, 1B) isolated relay contact will be activated to indicate ‘Battery OK’ status. This relay contact functions as a summary alarm and is typically connected to the site’s central alarm system.
