Batteries in fire / security control panels need to support the alarm in the event of primary power failure and enable activation and support of the warning circuits for minimum periods under alarm conditions. The reliability of these batteries is vital. Not just property but lives may depend upon them.
"...battery testers that test a battery under no load do not accurately simulate the battery's performance in operating conditions..."
Besides being simply discharged, there are a variety of factors that can cause batteries to fail, including:
- Battery chemistry being out of specification
- Mechanical connection failure within the battery
- Sulfate build up on the plates (of SLA's)
- Age and storage conditions
- Manufacturing defect
A failing battery reduces battery performance and power output. Today, most battery operated devices employ microprocessor based circuits with internally programmed 'cutoff' voltage. The cutoff voltage varies with circuit design, but when supply (battery) voltage falls to 'cutoff' level under operating load, the circuit will shut down. Reliability of battery operated devices is, therefore, not merely a function of battery capacity, but also voltage under operating load.
A battery with 60% remaining capacity is useless if the battery cannot deliver current while maintaining voltage above a device's 'cutoff' level. So, when testing a battery, it is very important to be able to accurately determine available power capacity (capacity that can be delivered at the necessary voltage).
There are several different methods of battery testing in use today. All have drawbacks (see 'the alternatives'). Capacity is useless if the battery can't deliver its current at a voltage above a device's cut-off level and a battery with 60% remaining capacity but inadequate terminal voltage is not going to be fit for purpose.
Methods are often selected either on the basis of specific battery type or chemistry or because they are quick, convenient or cheap. Load testing, arguably technically the best method, usually does not get done because of the time that traditional load testing takes, because traditional load testing can cause battery drain and because load testers are traditionally expensive and unwieldy. Until now:
Pulse load testing is now considered as the most accurate form of testing as it produces results which are based on evidence of the battery's actual performance under load.
