Strange issue with LOW BATTERY message

[HoustonFirefox]

Hello All,

In the last few days I've run into an issue with my Elk M1G I hope someone might have some insight into.

My Elk has been running fine for the last 1.5 years with two Elk batteries wired in parallel. Recently I've been getting a LOW BATTERY indication on the keypad. If I left it alone, eventually the display would go dark but the power light on the main control would stay lit. The system would not arm or go into alarm in this state. If I turned it off and then back on it would run for about 5 minutes before going dead again.

Now for the fun stuff. The system can only be powered up with the battery installed. If I disconnect it and try to power up, nothing will happen. If I disconnect the power plug at the control it reads 18.2vac but if I plug it back in with the unit off, it still reads the same. When I turn the unit on the voltage drops to 10.8 vac if the battery is charged and .2 vac if the battery is very low (I think the PTC breaker trips trying to recharge the low battery).

Out of curiosity to see if I might have a bum battery, I pulled the 12vdc gel cell from my APC battery backup and measured 13.8vdc with no load (fully charged). I put it in the Elk last night and performed the load test - All Okay. When I checked it this morning, the keypad was once again displaying "LOW BATTERY".

The power brick for the Elk has a green light on it and "appears" okay but I'm wondering if it is failing since it doesn't seem to supply the Elk under any type of load and certainly is not float-charging the battery.

Any ideas?

 

[Spanky]

Sounds like you are drawing enough current from the transformer to kick in the PTC resettable fuse or the PTC fuse has degraded. You should be getting 16 to 18 VAC under load coming out of the transformer. If not, you are not recharging the batteries.

Unplug the transformer and measure the current coming from the batteries into the control to see what your system current is. Stay below 1.5 amps to leave room for battery recharge and alarm current.

Allow the transformer to cool down for an hour and put it back in service. Measure the transformer voltage and see what it is at. If it is OK, let it remain in service for a day and measure again. If it has cut back again the transformer could be bad and / or you are drawing too much current on your system.

 

[HoustonFirefox]

Spanky, thanks for the advice. I replaced the transformer but that didn't solve the problem. The system will only run on charged batteries with the AC adapter plugged in. If the batteries are disconnected and the unit powered up, the voltage drops to .02 volts at the 16vac input to the Elk with everything except the data bus disconnected. If I unplug the data bus, the AC input jumps up to a mere 6 volts.

Running:

5 Motion Sensors
1 Z-Wave interface
1 4-wire Smoke/Heat (more on the way)
1 Z-Wave interface
1 Keypad
1 Ethernet interface
1 input expander

I spoke with Brad at Elk and he seems to think the charging circuit has a problem. I'll have to pack it up and ship it back to Elk and see what happens. Feels creepy not having any alarm functionality during this time (I go out of town on business frequently).

I'll update everyone here on the what went wrong, what the turnaround was and any costs involved.

 

[Spanky]

Sound like the power supply has a problem. If you disconnect the battery and measure the voltage on the battery leads, it should read 13.6 to 13.9 volts.

 

[HoustonFirefox]

It's been awhile since I posted this and realized I never followed up with what the problem was.

Well, it started happening after an extended power outage and the system was running on it's two batteries in parallel for about 7 hours.

I sent the control back to Elk and they graciously diagnosed the problem and found a bad diode in the charging circuit.

I used to be an Electronics Technician in the Navy (many moons ago) so here is what I think happened:

1) Since the Elk is running two batteries in parallel, they probably got very low during the long power outage.

2) When the power came back on, I'm guessing that the Elk attempted to charge them and the amperage exceeded the current capacity of the charging ciruit resulting in the blown/shorted diode.

This is just a guess on my part. The diode could have been mediocre when it was new or maybe a spike got to it or something. Anyways, just thought I'd follow up and let everyone know it's been back in operation for some time now.

Damn you feel vulnerable when your control board is in the mail!