Power supplies vary in the features they offer relating to battery backup. A few
considerations are:
• Deep discharge – When a backup battery is drained too much it can reach a state
whereby it cannot be recharged. This is deep discharge. Some power supplies have
the ability to prevent this happening.
• Recharge limit – Some power supplies limit the current consumption of a battery
whilst it is recharging. If a power supply does not do this then the system may not
be immediately operational when mains power is resumed, i.e. the power will be
consumed by the battery recharge.
• Battery capacity – the size of the enclosure will limit the amount/size of the
backup batteries.
Chapter 2 About 8