Access Easy Controller
APPENDIX B Selecting A Correct Battery Size | en
189
Bosch Security Systems
Hardware Manual
Ver 2.0.0 | 2006.07
26
APPENDIX B Selecting A Correct Battery Size
This section provides the System Installer a quick and easy way to determine the battery size
to use based on the hardware configuration and total current consumption of the whole sys-
tem.
26.1
How to choose the correct battery size for your application
Figuring out the size of a battery necessary to support the load discharge current for a specific
amount of time can be tricky. Batteries are rated at maximum efficiency over a 20-hour dis-
charge period. Therefore, a 20AH (Ampere-Hour) battery will provide 1A over a 20-hour
period. However, calculating the discharge currents is not as easy as division or multiplication.
A 20AH battery that supplies 1A for 20 hours will not provide 2A for 10 hours, but rather, 1.8A
for 10 hours, which is equivalent to 18AH.
In order to facilitate calculations to determine the correct battery size for chosen discharge
currents and discharge times a chart is drawn up (Refer to next page).
To use the chart, simply match the load discharge current requirement (in Amperes) along the
bottom of the chart (x-axis) with the desired discharge time (in Hours) on the left (y-axis). At
the intersection of the two lines, find the diagonal line immediately above that point, which
then represents the minimum battery rating needed (in AH).
The next page provides a simple example with the chart.
