Every refuge chamber requires an emergency power source to maintain the life-sustaining equipment if mains power fails. An uninterruptible power supply (UPS) differs from backup generators in that it provides almost-instantaneous protection from power interruptions. How can you ensure the performance and longevity of an uninterruptible power supply underground?
The MineARC Satellite UPS System (SUPS) is a unique, portable battery bank; removing the need for integrated battery and inverter storage at the rear of the refuge chamber. Significant features of the Satellite UPS System includes safer battery handling during replacement, charge balancing, temperature cooling, and improved battery monitoring and diagnostics through MineARC’s GuardIAN Refuge Chamber Monitoring.
The three unique features that work toward extending the life of the battery systems include cooling, balancing, and monitoring.
1. Satellite UPS Temperature Control
As heat significantly impacts the life of a battery, active cooling systems are required to combat harsh atmospheric conditions.
In reference to battery management, temperatures above 25°C are considered high. Anything above this mark will cause excessive stress on the batteries resulting in the depletion of battery power over a shorter period. The life of a battery will decrease by half with every 10°C rise in temperature – and this damage is irreversible.
The hotter the battery, the faster chemical reactions will occur; often resulting in damage to the internal structure of the battery due to fluid evaporation.
Battery Cooling Solutions
- Artificial Cooling: An internal air conditioner within SUPS provides consistent cooling
- Dissipation of Heat Generated: SUPS is designed to maximise the natural process of heat flow caused by battery convection, conduction and radiation
- Monitoring: SUPS protects against overheating by proactively managing and monitoring heat distribution
2. Battery Balancing
Charge balancing involves the ensuring the even distribution of energy among each cell in a string of batteries. Without balancing, a portion of the power within the battery is wasted.
Within SUPS, cells are sorted by state of charge (SoC) and control charging, with compensation for temperature in strings appropriate to system voltage (48V or 24V – 4 x 12V battery strings).
Battery balancing across the strings is achieved by utilising Linear Technology, LTC3305, as shown in the diagram below. This standalone lead-acid battery balancer can support up to four cells, using a fifth reservoir battery cell (AUX). The AUX cell continuously places itself parallel with each cell, to balance all of the battery cells. By absorbing charge from higher voltage batteries and transferring that charge to lower voltage batteries, the balancer ensures each cell is charged equally. This extends the cell cycle life and provides an added layer of protection by counteracting damage to a battery due to deep discharging rather than overcharging.
3. Uninterruptible Power Supply Monitoring & Diagnostics
Through MineARC’s GuardIAN Refuge Chamber Monitoring, faults within a battery stack can be quickly identified and appropriate action taken to reduce the adverse effects of a poor performing battery. Changes in battery condition and performance are communicated to the control room in real-time, where analysis of the data allows for controlled measures to be activated or replacement to be scheduled.
Battery maintenance costs are reduced through enhanced charge control and balancing as well as improved testing and ongoing monitoring. With the Satellite UPS System linked to GuardIAN, each cell in the battery stack is monitored to maintain a healthy battery state of charge.
Safer Battery Replacement
A compact and portable design enables the Satellite UPS to be brought to the surface for maintenance or battery change-out. Reinforced sliding draws house the batteries and allows for a top-down installation and removal process; ensuring a safer lifting technique is employed and reducing the risk of injury during battery replacement.
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