Eurosec CP8L strange fault

[Dan Carron]

A friend has a CP8L Eurosec alarm system, installed several years ago. The sensors, a mix of contact and PIR, are all wired, ie no batteries. The main panel has a Yuasa 12V 3.2Ah backup battery.

The keypad unit is showing a LOW BATT alarm message which prevents the system from being set. Quiescent battery voltage with 240Vac mains connected is 13.65V (manual says DC supply is regulated 13.8V so this seems close enough to me). On removing mains power the battery voltage slowly drops to about 12.5V (pretty standard for a Yuasa backup battery) and the keypad panel works ok (but system still won't set). The fault occurred one day when he was out

I haven't yet tried a total removal of power (mains and battery), but could do this as a last resort. I'm presuming the configuration is non-volatile, ie will persist with all power removed, can anyone confirm this?

Any suggestions?

 

[sparkymarka]

Pretty simple REPLACE THE BATTERY

 

[Handymanjo]

Yes replace the battery. Checking the battery with multimeter does not prove that the battery is OK.
Are you shore it is a CP8L and not a CPX ?

 

[Dan Carron]

Thanks to both respondents. I'll replace the battery - should I disconnect the mains supply first or is it ok to do it with the panel powered up?
Regarding the DVM check - this was done with the battery in-situ and connected to the panel, ie either being charged (mains on) and supplying current (mains off), which strikes me as a pretty reasonable way to check the battery status as it's under operating conditions.

 

[Dan Carron]

ps The user guide and installation guide are both CP8-L documents so I'm presuming that's what it is.

 

[Dan Carron]

Update: We didn't get as far as changing the battery. Thought I'd check the fuses on the pcb and whilst both looked in-tact a pd check across them revealed the 1Amp Quick-Blow fuse had blown. Removed the (old) battery, changed the fuse, reinstalled the old battery and the LOW BATT alarm cleared and a quick test on the system indicated it was working normally. I would have been happier if it was a battery fault because that's fixed by changing the battery. What concerns me more is the cause of the fuse blowing, I suppose it could be the battery with an interesting failure mode, but we'll see. My friend is going to keep an eye on the system over the next week or so, we'll then try turning off the mains and running it on battery to see what happens. Watch this space.

 

[Handymanjo]

You ideally need to test battery with a battery tester which tests the battery under load.
Testing with multimeter will only give you the voltage of the battery.
How old is the battery?
Older than 5 years you should change it. For a fuse to blow they must be a cause ?

 

[Dan Carron]

Battery was replaced in 2020, agree there must be a cause for a blown fuse hence the plan to keep an eye on the system for a week. My friend has got a new battery so we'll put that in at some stage, but IMO changing one thing at a time is usually the best approach to fault finding in any system.

 

[Handymanjo]

Does the battery lead have a in-line fuse holder ?

 

[Dan Carron]

Don't think there's an in-line fuse holder, the fuse which blew was on the pcb (two fuses side by side, the RH one as viewed from the front). Will check for an in-line holder when I'm next at my friend's house. It'd be interesting to have a look at the circuit diagram of this system, but I guess that would be treated as IPR and (understandably) not available. Not practicable to reverse engineer it as the pcb has surface mount components and is (I suspect) multi-layer or at least double sided and even if it wasn't it looks complicated enough to be a non-starter.

 

[sparkymarka]

Have you taken a reading from the battery terminals without a battery connected ?

 

[Handymanjo]

The early versions of the eurosec/cpx range had in line fuses in the battery leads to prevent faulty batteries blowing aux fuse on pcb.Years back this did cause some issues and you needed to check the fuse holder had good contact with fuse in the holder.
They has since changed the pcb,but years ago.

 

[sparkymarka]

The early ones didn’t …..then they did ……then they didn’t …..lol

 

[Dan Carron]

No, haven't taken a reading in that set-up, but agree it's a good idea to do it. The 13.65Volts (see original post) measured with the battery in-circuit indicates it's very likely that it is/was being charged, so presumably the 1A QB fuse (which I assume was blown when this all started) only protects the battery when it's supplying current to the unit. For this work there must be diodes in the circuit or some more complicated arrangement to achieve the 12V (nominal) supply changeover. I'm not up to speed with the standards for Grade 2 alarm systems, presumably they're required to monitor battery voltage when the mains are connected which seems an eminently sensible thing to do.

 

[Dan Carron]

ps Thanks to both correspondents for engaging in this, helpful to me and may also help folks in the future (not that this issue has been fully bottomed out yet).