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Last update:
11th April 2003
SmartControl - Information
SmartControl is a new technique that, in addition to the benefits achieved through IMS monitoring, provides better determination of battery State-of-Charge, and extends battery life in standby applications. SmartControl operates the battery predominantly in open circuit, with intermittent charge recovery to maintain capacity, and the ability to support load instantaneously.
Under the direction of a SmartMonitoring IMS (Intelligent Monitoring System), this proprietary intermittent charging technique controls battery current using a special diode-switch device. The diode provides instantaneous connection of the battery to the power supply rail during discharge and other events that require the battery to source current (eg. clearing of fuses/circuit-breakers due to downstream faults). The Power Mosfet provides a very-low resistance switch to either assist the diode when it’s conducting, or to connect the battery to the power supply rail for charging.
Because the battery typically operates in open-circuit, State-Of-Charge (SOC) is simply monitored from terminal voltage. The advanced cell-level monitoring provided by the IMS ensures the integrity of the battery is known whether in open-circuit, charge, or discharge.
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The diode-switch device is manufactured in a fuse foot-print, and housed in a fuse-carrier to allow easy installation and to act as a load-current disconnect switch. The specification for the diode-switch is:
High reliability operation of the diode-switch device is achieved through redundant fail-safe design, and monitoring. The diode-switch device has a MIL-HDBK-217F(2) predicted MTBF of 68 years (series reliability model, ground benign environment factor = 1, commercial quality parts factor = 10). |
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Extending battery service life with open-circuit operation and intermittent charging
In most telecommunications standby power systems, lead-acid batteries are deployed in a manner where the battery spends the majority of time operating in a float condition. In a float condition, a small current passes through the battery that effectively replaces capacity lost due to self-discharge and maintains the battery at full capacity. The battery experiences both electrochemical and chemical modes of degradation, and these degradation modes predominantly determine the service life of the battery.
An equivalent situation exists with Uninterruptible Power Systems (UPS), but in this case the battery also typically sees much higher levels of ripple current which degrade battery life at an even faster rate.
In an open-circuit condition, with no current passing through the battery, the battery experiences only chemical modes of degradation and can exhibit a comparatively longer service life. References show that batteries operated under open-circuit conditions, compared to batteries operated under float conditions, can exhibit up to a 100-200% extension in service life. The literature has generally coined the term "intermittent charging" to refer to methods of charging the battery, whereby the battery does not receive a continuous charging current, and operates for a substantial period of time in an open circuit condition.
Telepower Australia presented a conference paper at INTELEC 2001 titled "Some advances in control of telecommunications DC power systems", which includes more information on this topic - see our bibliography.