First Alert Smoke & CO: Battery level report very wrong...?! CHIRP! CHIRP!


(ActionTiles.com co-founder Terry @ActionTiles; GitHub: @cosmicpuppy) #1

So I had one of my First Alert Z-Wave ZCOMBO Smoke & CO Detectors go into the dreaded (though not as bad as fire! :fire:) “low battery chirping mode” this morning.

Exactly one of the situations I was hoping to avoid by using a “smart” device. :crying_cat_face:

According to the “Recently” tab, at 8:15am the battery was reported to be 77% (history shows a drop from 79% to 78% over the last 6 days … seems perfectly normal). In other words: *there was apparently sufficient battery and connectivity to a rather more than sufficient battery capacity at 8:15am& … I’m not sure what time the chirping started though!).

I took out the batteries and re-inserted. The device promptly reported battery level as 1%!

Of course, if the device were a little smarter, then it should offer an additional special “low battery alert” message that corresponds exactly with the start of chirping (or perhaps at a level that is typical of 24 hours before chirping?..), but absent that, I wonder what’s happening here.

This unit uses 2x1.5v AA batteries. Checking with a multimeter, the batteries have about 1v each. I understand that “low voltage conditions” are necessarily considered linear to “battery capacity”, so (1v+1v)/(1.5v+1.5v) = 66% normal voltage does not necessarily correspond to 66% battery capacity.

In other words, I could say the batteries are pretty close to the 77% reported, but I also could understand if the device thinks that 66% is too low and warrants chirping, but how can it report 77% one moment, and 1% after just inserting the batteries the next moment?

I’m going to put the same batteries in a second device and see if it also reports 1%; though I’m not sure that information will help contribute to this problem.


2016-11-30 11:39:22.097 AM PST
19 minutes ago	DEVICE		battery	1		Den Smoke CO Alarm battery is low!	true
2016-11-30 10:48:33.134 AM PST
1 hour ago	DEVICE		alarmState	clear		Den Smoke CO Alarm test cleared	true
2016-11-30 10:48:33.134 AM PST
1 hour ago	DEVICE		carbonMonoxide	clear		Den Smoke CO Alarm carbon monoxide is clear	true
2016-11-30 10:48:33.134 AM PST
1 hour ago	DEVICE		smoke	clear		Den Smoke CO Alarm test cleared	true
2016-11-30 10:48:32.226 AM PST
1 hour ago	DEVICE		alarmState	tested		Den Smoke CO Alarm was tested	true
2016-11-30 10:48:32.226 AM PST
1 hour ago	DEVICE		carbonMonoxide	tested		Den Smoke CO Alarm was tested	true
2016-11-30 10:48:32.226 AM PST
1 hour ago	DEVICE		smoke	tested		Den Smoke CO Alarm was tested	true
2016-11-30 10:48:26.854 AM PST
1 hour ago	DEVICE					Den Smoke CO Alarm code 13 is 0	true
2016-11-30 8:15:40.710 AM PST
4 hours ago	DEVICE		battery	77		Den Smoke CO Alarm battery is 77%	true
2016-11-30 7:25:17.971 AM PST
5 hours ago	DEVICE		battery	78		Den Smoke CO Alarm battery is 78%	true
2016-11-28 6:55:55.265 AM PST
2 days ago	DEVICE		battery	78		Den Smoke CO Alarm battery is 78%	true
2016-11-26 4:34:11.408 PM PST
4 days ago	DEVICE		battery	79		Den Smoke CO Alarm battery is 79%	true
2016-11-24 4:12:28.679 PM PST
6 days ago	DEVICE		battery	79		Den Smoke CO Alarm battery is 79%	true

Battery: Goes from 70% to 1% First Alert 2-in-1 Z-Wave Smoke Detector
#2

Funny you posted this because mine has been stuck on 100% for months. I just now tried to reset it and then the low battery notification went off showing an update at 100%. Not sure whats going on with these.


(ActionTiles.com co-founder Terry @ActionTiles; GitHub: @cosmicpuppy) #3

Yah… that’s rather annoying. Of course, as long as actual Smoke & CO alerts get transmitted, that’s more than half the value.

But avoiding the chirp and proactively replacing batteries would sure be a nice benefit.

There are other brands to consider, but First Alert seems to be good quality in general (and a great bargain compared to Nest or whatnot!). An “alarm detector” wouldn’t have the battery reports anyway.


(Scott Clausen) #4

Be advised that current CO detectors have a five year end of life timer that forces you to replace them. This is from the date of manufacture and a replace by date is usually printed on the back. It wouldn’t surprise me if the warning was similar to a low battery chirp. Not saying that is your problem but it is something to consider.


(Michael Hess) #5

My Insteon Smoke Bridge is supposed to alert to low battery as well, never has, not once, with 4 OneLink detectors. I think the devices just stink at reading the level.


(Jeremy Keen) #6

Same issue here. Super annoying as they seem to hit the chirp warning level at 2am. I am going to proactively replace at 77% as 76% seems to be about where it starts to chirp. Another interesting thing, I hit the test button the detector on one that was around 77% and sure enough it jumped down to 1% and started chirping!


(Michael McGrath) #7

My First Alert Z-Wave smoke detectors start chirping at 77% – this has happened twice now. The device handler should send a notification when the battery level is at 78%. That would provide about one week of leeway time to change the battery before being woken up in the middle of the night. I am glad that SmartThings is open and provides an opportunity to fix the battery reporting problem.


(ActionTiles.com co-founder Terry @ActionTiles; GitHub: @cosmicpuppy) #8

The challenge? … Even though the battery level is shown in percent %, the actual resolution of the battery voltage meter in the smoke detector may be much lower.

It might, for example, show 88% for weeks and then drop directly to 77%.


#9

Keep in mind when testing batteries with say a dumb tester (cheap) or even a DVM that the reading will be higher then what a device will report as there is no load on the battery when testing with a dumb tester (cheap) or even a DVM.


(Michael McGrath) #10

Although with duty-cycled devices that are designed for low power operation, the voltage under test shouldn’t be too far away from open circuit voltage, and irregardless, the behavior with my alarms is repeatable, and that is why I posted to provide two data points. Both of my incidents involved First Alert Z-Wave alarms manufactured in Q’3 2015; one detects smoke, the other also detects CO. Both started chirping immediately after reporting a battery level that showed up in my SmartThings logs as 77%. Both of the previous battery levels were 78%, and had been at 78% for at least one week. So the resolution on the First Alert alarms is 1% decrements. Both were running on the original Duracell AA alkaline batteries included in the package. My multi-meter read both batteries at just above 1.3 Volts; 77% of 1.5V would have been 1.15V under load. I think the behavior for new alkaline batteries is predictable with a nice linear slope. I plan to change my device handler for the First Alert alarms to reinterpret the battery status message range so SmartThing’s Device Health will warn me with enough time to avoid the midnight chirping incidents.
I certainly don’t expect known, predictable behavior with other battery chemistries or unbalanced alkaline pairs, but I am okay with the extra cost of using new alkaline batteries once a year in smoke and CO detectors.
YMMV, but this is an easy problem to address with a couple lines of code.
I haven’t looked into finding or creating a tool that saves and analyzes logs to automatically generate corrective battery status indicator curves. I do use rechargeable batteries in other sensors that are non-essential, and in those I observe consistent and reliable underreported values, but I take care to match and group rechargeable batteries by writing on them. Thanks.


(ActionTiles.com co-founder Terry @ActionTiles; GitHub: @cosmicpuppy) #11

The source code for the Z-Wave Smoke Alarm (including First Alert Combo) is available if anyone wants to modify it.

SmartThings will even often accept and merge changes into the official DTH, via a “Pull Request”, if they are minimal and well tested.


#12

Is there an app out there that will alert when the battery reaches 78%? Most of my detectors update battery levels correctly but of course ST won’t alert me of a low battery condition until well after they hit 77% and start chirping at 3am.