Advanced Monitoring

Advanced functions and features can be found in many modern battery monitors, including:

• Time Remaining—Provides a rough estimate of how long the batteries could sustain a given load based on time-averaged increments (i.e., 4, 16, or 32 min.).

• Cumulative Amp-Hours—A cumulative count of Ah in or out of the batteries. Useful in estimating battery age or total charging-source production.

• Peukert Exponent—Factors in the discharge rate's effect on battery capacity.

• Charge Efficiency Factor—Accounts for charging efficiency losses.

• Multiple DC Inputs—To monitor more than one battery bank, charging source, or load simultaneously.

• Data Logging—Uses a communication port to export data to a computer, a data logging device, or the Internet.

• Remote Display—Allows a separate display to be conveniently mounted away from the monitor.

• Usage Readings in kWh—Make it easier to directly relate the amount of remaining battery capacity to the load ratings of household appliances.

• Relay Control—Activates a relay at a preset voltage point to start a generator, manage a load, etc.

• Alarms—Signal low battery, loss of meter power, etc.

• Battery Temperature—A sensor can be placed on the battery and wired into the monitor to report battery temperature.

Once the meter is mounted, a few basic user inputs must be manually programmed into the meter. First, program the Ah capacity of the battery bank into the monitor. Without this, the monitor cannot calculate the battery SOC. Be sure to specify the capacity at the battery's most relevant rate. Taking into account Peukert's Law, battery manufacturers list different Ah capacities for the same battery because a battery's capacity is lessened the faster it is discharged. A battery's capacity at a 20-hour discharge rate will be greater than at a 5-hour rate. For most renewable energy systems, the 20-hour rate best reflects how the battery will be operated.

The final manual programming tells the monitor when to consider the batteries fully charged. When the monitor detects that the high-voltage set point and the low-current threshold have been met, it assumes that the batteries have been fully charged and are now in float mode (where a low-current charge keeps the battery full). This automatically resets the "amp-hours from full" display, with the monitor reading "100%" or "Full," and sets the "days since fully charged" number to zero.

With a few minor programming details—such as selecting the desired battery reminders/alerts—and a thorough reading of the manual, your monitor will be up and running. Oh look, the bank's at 14.8 volts, I've got 18 amps coming in from the array, and it's been seven "days since laundry." Gotta go!


Khanti Munro ([email protected]) instructs, coordinates, and develops curricula for the PV online program at Solar Energy International. He is an ISP Certified Instructor for Photovoltaic Courses and has been designing, installing, and educating about solar-electric systems since 2002.

Battery Monitor Manufacturers:

Bogart Engineering • • TriMetric & PentaMetric monitors

OutBack Power Systems • • FLEXnet DC battery monitor

Xantrex • • TM500A, Link 10, Link 20, LinkLite & LinkPro battery monitors

Now available in the US & Canada

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