Is this correct?

[BHCC]

Afternoon

I have just been reading BS5839-1:2002 to check on the periodic inspection recommendations (page 107) and it states that 'The standby battery should be disconnected and full alarm load should be simulated'

I was always under the impression that the full load test should be done with the mains disconnected to check the discharge of the batteries.

Can anyone help??

Thanks

Mark

[Wiz]

The power supply of the fire alarm system should be of sufficient capacity to power the system without a battery connected to it to ensure the full alarm load can be supplied with the mains only connected, in case of failure/disconnection of the battery. The BS recommendation you highlight is a test of this. BS 5839 part 1 2002 45.3. d).

The load testing of the battery is covered by BS5839 Part 1 2002 45. 3 e)

In my opinion the use of the term 'load testing' in respect of testing of the batteries is not an indication that they should only be tested by operating the alarm load from the batteries. It is almost certain that any battery set in anything but the poorest conditon will achieve this for at least a couple of minutes. In my opinion the 'load test' should involve connecting a load providing a known and sufficiently heavy discharge current to the batteries and monitoring the battery voltage over a period of time to ensure that the battery voltage follows the manufacturer's discharge rate data for that battery.

In my experience I have found that connecting a load of approx. 1/20th of the battery's stated AH capacity (i.e. approx 350mA for a 7AH battery or 1.2A for a 24AH battery) over approx 30 minutes will give a good indication of that battery's condition. A good 24V set will normally start at about 27V and drop to approx. 22V over 30 minutes. A poor set will drop to approx 22V in just a couple of minutes or to less than approx 18V in approx 30 minutes. There are also automatic battery condition testers available on the market that do the calculation of actual battery capacity remaining in a battery.

[Allen Higginson]

I have had this proved in practical terms where a control panel would not drive the system unless the batteries were connected (ie - the panel was faulty).

[David Rooney]

In my experience I have found that connecting a load of approx. 1/20th of the battery's stated AH capacity (i.e. approx 350mA for a 7AH battery or 1.2A for a 24AH battery) over approx 30 minutes will give a good indication of that battery's condition. A good 24V set will normally start at about 27V and drop to approx. 22V over 30 minutes. A poor set will drop to approx 22V in just a couple of minutes or to less than approx 18V in approx 30 minutes. There are also automatic battery condition testers available on the market that do the calculation of actual battery capacity remaining in a battery.

I agree, I used to use various 200w resistors... lost my finger prints once or twice when i forgot how hot they got....!!

[Graeme]

never been brave enough to try resistors. I have the battery tester.

[Benzerari]

Afternoon

I have just been reading BS5839-1:2002 to check on the periodic inspection recommendations (page 107) and it states that 'The standby battery should be disconnected and full alarm load should be simulated'

I was always under the impression that the full load test should be done with the mains disconnected to check the discharge of the batteries.

Can anyone help??

Thanks

Mark

To be honest, I do both, I test the system, with (mains ON and batteries disconnected), and test it again with (batteries ON and mains disconnected). Just to make sure both feeds are OK. And it does not really take longer time... if you say, is that required by BS5839? my answer is I do not know, there are more experts who knows the BS5839 by heart... as for me I have to consult it each time I need to...

However, about the use of the battery tester, I used to forget to test the current drawn from the batteries when using a normal meter, but since I start using the battery tester, I found it really useful, because it reads the voltage, the current, and the temperature too, as this later has a negative effect in the life cycle of the battery, for each 10 degrees increase in temperature, the life cycle is dropped to half....

[Graeme]

just re read your question and Benz picked up on it.

yes you are required to test the control panel in full fire condition with mains and no battery and then battery with no mains.

The test with mains only is to test the power supply can cope especially in older panels

[Wiz]

In response to various comments added after my original post.

1) BS definitely recommends that a test by operating the system in alarm mode with standby battery disconnected should be carried out.

2) Battery temperature also affects the rate at which batteries need to be properly charged. Some charging circuits include a thermistor that should be placed adjacent to the batteries to enable the charging circuit to automatically adjust charge rate depending on battery temperature.

3) Many older systems (particularly those that used ni-cad batteries or older 'wet' cell battery sets) used a 'float' charge system where the power supply/charging circuit basically only had enough output to power the quiescent load of the system and then also keep the battery charged. larger loads (typically when the system was in alarm mode) would take the additional power requirement from the battery i.e. an alarm load would be discharging the battery even though the mains supply was connected and the charging circuit operating correctly. In these systems the disconnection of the battery would mean insufficient power was available to supply the system in alarm. Current recommendations require the power supply to cope with supplying the system load in alarm even with the batteries disconnected.