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[Oldtimer]

About 3 days ago my macros stopped working after having worked fine since I got my CM15A about two months after it was introduced.  RF commands were still picked up by the CM15A and repeated onto the power line properly.

I tried downloading my program again but no luck.

When I checked the battery status in the hardware configuration window in AHP I noticed a little red dot where there used to be a green one.  When I checked the batteries in the CM15A I found they were way out of the green zone on the tester and half way to zero.

Putting in new batteries and downloading the program again restored full operation and changed the red dot back to green.

Anyone else run into this situation?  Is this how the CM15A tells you about bad batteries?  I would think that as long as the CM15A was plugged in it would still run whether the batteries were good or not.

[-Bill- (of wgjohns.com)]

My CM15A ran fine until the power failed for a short time.  When I checked the batteries, I found that they were so low that a couple of them had leaked!  At present, it is running without batteries at all and seems to work fine!  I expect that the next serious power blink will require me to re-download timers & macros, but as you said, as long as it has AC power, it doesn't appear to need the batteries to keep working.

[Puck]

Oldtimer & Bill, I just looked at the schematic to see how the batteries are used.

Thru a voltage divider they turn on a transistor switch [when good] and set Port 0 - Bit 7 low.

The output of a linear regulator [+5V] is the pull-up. So when the batteries drain, and the transistor switch turns off, the line goes HI.

The input to the regulator comes from the AC [when plugged in] or the batteries [thru a protection diode when unplugged]. That's how the batteries maintain the +5V during a power outage to keep the micro-controller's RAM alive.

Since you both had/have it plugged in with drained/no batteries, you should have seen the same results. I suspect Port 0 - Bit 7 is just meant to set the battery status indicator [red or green]. But from what Oldtimer has seen, maybe since the transistor driving the Port 0 - Bit 7 input doesn't have hysteresis, it caused an undefined logic level [0.8V to 2.4V] and messed some internal logic up.

Bill: Out of curiosity, without batteries installed, are you seeing the Red Status Indicator in the Hardware Configuration window?

It will be interestring to hear of others experience with low batteries. 

[-Bill- (of wgjohns.com)]

Bill: Out of curiosity, without batteries installed, are you seeing the Red Status Indicator in the Hardware Configuration window?

Yes, the Status Indicator in the Hardware Configuration window is Red with no batteries installed.

[Knightrider]

I think this thread needs to be bumped back into the spotlight.  Seems to me that my first CM15A went bad when the batteries ran out.  Currently, it only sends RF and no PLC.  My new CM15A behaves much like the one that Bill describes.
Date code on old CM15 : 06a01
Date code on new CM15 :07a04
Anyone else see anything like this?

[DeanKS]

My CM15A stopped working. Unplugging AC and USB did not help. Computer stated that there was an error in the USB device. So I pulled out my new spare unit and plugged it in, works great. So I transfer the add-on antenna from the old to the new. Noticed that the units have backup batteries, I had forgot. I move the batteries to the new unit, there was 5.7V across the 4 cells, that should work. Seems to work fine, but Active Home Pro gives them a code red.

Started thinking... maybe the old unit was in a logic glitch and the battery was maintaining that state. Connected the old unit, with no batteries, and USB connection was error free, downloaded settings, no problem. So my instinct seems valid. And perhaps extended time disconnected from 120VAC was part of it.

So I still have a spare and this time the added antenna is mounted better.

[Brian H]

One of the things we frequently recommend. Is removing the batteries, disconnect from the USB port and unplug from the AC. To completely reset a CM15A.

[dave w]

Started thinking... maybe the old unit was in a logic glitch and the battery was maintaining that state. Connected the old unit, with no batteries, and USB connection was error free, downloaded settings, no problem.

Maybe the old dead batteries were loading down the CM15A power supply. They shouldn't, as one would think X10 *had* an isolation diode in the loop, or the isolation could be bad. A test might be to plug the CM15A in without batteries and measure the + and - terminals of the battery string (upper left terminal and lower right terminal in the compartment?). I can't measure mine right now, but I would guess anything over a few tenths of a volt would be suspect. Compare your two units.

Brian H might know the answer off the top of his head.

When was the last time you changed them? Put the CM15A on your smoke alarm schedule...new batteries once a year.

[Noam]

When was the last time you changed them? Put the CM15A on your smoke alarm schedule...new batteries once a year.

I was always told that smoke detector batteries should be changed TWICE a year - when you change the clocks.

[Brian H]

dave w; Has a Schottky Diode isolating the battery 6 volts feeding a LDO regulator. Also has a low voltage sensing circuit that feed one of the IO pins of the controller.

Noam; I have seen some say twice a year and other say yearly. I do mine on back to EST in the fall.
I wounder if most users also read the sticker on them. Saying they should be replaced after so many years from the manufactured date.

[dave w]

dave w; Has a Schottky Diode isolating the battery 6 volts feeding a LDO regulator. Also has a low voltage sensing circuit that feed one of the IO pins of the controller.

Noam; I have seen some say twice a year and other say yearly. I do mine on back to EST in the fall.
I wounder if most users also read the sticker on them. Saying they should be replaced after so many years from the manufactured date.

Yeah, Shottky makes sense. So with batteries removed there should only be a few tenths of a volt at best across + and - terminals in the CM15A.

And I doubt but a few people are aware of the decay of the isotope in the smoke detection chamber. They probably think it is a way for manufactures to sell more smoke detectors. But I have at least one 20 year old that I know still works.  Don't ask how I know, but a hint is, it is located near my test bench.