Patent ID: 6917298

Claim:
A backup electrical power unit for use in providing a backup power supply to an alarm panel when primary power to the alarm panel is interrupted, said backup unit comprising: (a) a solar panel array, including an array output, said array producing an array DC voltage and a charging current at said array output; (b) a battery, including a battery terminal output having a battery output voltage; and (c) a first means, interposed electrically between said array output and said battery terminal output, for electrically connecting said array output to said battery terminal output at a first voltage level of said battery output voltage and for disconnecting said array output from said battery terminal output at a second voltage level of said battery output voltage, said second voltage level higher than said first voltage level such that a dead band is created between said second voltage level and said first voltage level, whereby said charging current stops flowing to charge said battery when said second voltage level is reached or exceeded, and said charging current does not resume its flow so as to charge said battery, until said battery output voltage drops to or below said first voltage level, said first means including circuit means for setting said first voltage level, said first means further including other circuit means for setting said second voltage level such that the dead band between the first and second voltage levels can be varied as determined by an operator.