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Circuits designed by David Johnson, P.E.
Last Updated on:
Monday, December 25, 2017 02:05 PM
List of Dave's Circuit Designs
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More
Battery Monitors
Indicators |
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Lead-acid Battery Low Voltage
Indicator |
Lead-acid batteries should not be discharged below a certain voltage.
Discharging a cell below about 1.8v and can often damage it, which will result in a
lower Amp-hour capacity. Large battery banks are critical in off-grid energy
storage systems. One bad cell in a series wired string will weaken the whole
bank. The circuits below are designed to be connected across either a single 2
volt cell or a 6v three cell battery bank. It will alert the user of a weak cell
by turning on a red LED when the cell voltages drop below 1.8v. The circuit
takes advantage of a low voltage LMP2231 op Amp from Nation Semiconductor and a LM385
voltage reference in the first circuit. In that circuit the red LED must have a
forward voltage of about 1.6v at 5ma, in order to operate properly. In the
second three cell bank circuit, a TLV3701 voltage comparator is used. The
circuits are simple enough that they could be placed on a postage stamp size circuit
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2v Lead-acid Cell
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6v Lead Acid Battery
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Click
on Drawing Below to view PDF version of Schematic |
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