replacing the CO detector

[skyrat]

Just contacted MTI and they are shipping a new unit today. This is a unit that has been supervisor tested, and I will return the one I have to them. They did say that the first unit returned did test for a bad part. Hopefully this is the fix! Very good customer support, and once I asked if I would have to pay for shipping again, the person checked with a supervisor and had a ship with a return label so that I would not have to pay a second time to return their unit.

I will keep you informed...

[skyrat]

I installed the new unit and all was well.
Then a week or so later, with the voltage reading 12v on my digital meter, the malfunction alarm is going off again. When I go to shore power and get up above 12v all is well. So, this one seems to be going off because of low voltage. The literature says that this should operate normally down to 7v.

I spoke with Jeff at Tech Support for MTI. Jeff KNOWS what he is talking about with these units, how they work and is super nice. It seems that there is a misprint in the users manual and that the unit will only operate correctly down to a little over 10.4 volts. Then you get a malfunction alarm that tells you the unit is not operating properly. I am bummed because I bought the unit thinking we might go low on the battery power some nights after being in one location for a while, and 7v gives us a lot of room before problems might arise.

While all three (3) of my Malfunction Alarms have happened at voltages of 11.7 or greater (though the cheesy plug in volt meter might not be accurate?) These late night alarms are taking the joy out of camping. Jeff said that there are makers of RV detectors that are purely battery operated that should solve the problem for me since the product is not working for my application, and that they would refund me the purchase price.

Now, I am looking for a battery operated combination Carbon Monoxide, LP Detector that is for RV use. Jeff said there is a definite difference between RV and home units because of vibration and temperature differences, etc. I have yet to find one that does both and is designed for RV's and is battery-only operated.

Does anyone have a unit that they can recommend?

[rallypanam]

Odd. You apparently have bad luck.

I replaced the original CO with the MTI CO and Propane a couple years ago, just to be on the safe side. No issue whatsoever, even at low voltage.

My GS3 propane detector was dead though, the PO had removed fuse, but as soon as I put fuse back in it would alarm, apparently signaling that it was dead. I replaced that with a new unit, and no issues since.

And my van is generally dirty, dusty, etc, and it doesn't appear to be an issue for me.

[Scalf77]

I guess I would say that at a 11.7 volts you are already low on your battery. It is possible that you have a voltage drop from the battery or from where your reading it or both to what is really getting to the detector. You should try measuring the voltage at the detector. Specifically watch when a load like the refrigerator comes on, do you see a dip. Make sure you have a good ground connection and such. Once you have three "Bad" units I would start suspecting something else.


-greg

[skyrat]

I suspect that only 1 was actually "Bad." That one was confirmed when they tested the return. The others were probably low voltage causes. It just did not seem like it could be so when the manual told me I still had almost 4 volts above the lowest recommended. Now that I know that the minimum voltage is over 3 volts higher than stated, I suspect low voltage is the real cause, since they signal the same alarm malfunction. I will check, with a real voltmeter, at the detector, when I remove it, and see if the numbers match the cheesy plug in battery tester. I ran the measurements from the 12v socket about 18" to the left of the units mounting location, though I do not know if the socket is on the same line as the detector. Thanks for the suggestion to measure at the device. If the cheesy tester is off, this could answer the whole question.

Yes, the battery is getting low at 11.7v, still almost 1.5 volts more than the manufacturer says the unit needs, but sometimes that is just the way it is. Sometimes my battery gets low if we have had heavy usage and don't have shore power or run the engine. I prefer the detector doesn't wake me in the middle of he night-just to let me know. I get that it is a safety device and that while most things just slow down when the voltage gets low, this has other responsibilities.

Has anyone else had alarms when the voltage gets lower?
At which voltage did yours alarm?
Anyone know of a battery only unit, either LP or MO or Combo that you can recommend?
"I gots ta know!!"

[rallypanam]

Originally Posted by skyrat

Yes, the battery is getting low at 11.7v

If your battery regularly gets to 11.7v it isn't low, it's mortally wounded.

[skyrat]

Regularly?
First, I went back and re-read my post on page 2 of this thread. It got down to 11.9v not 11.7. So, those two tenths were on me. That was the lowest I have ever measured, unless I am forgetting something, in my SMB.

That was the first malfunction, and acknowledged by them as a faulty internal part. The other two had voltages at 12 or higher, but when plugged into house power and over 13v, reset to normal. The last one the van sat for about a week, unplugged, using the fridge for about 2 days and occasional interior light use, and house battery stereo use for 2 days during that week. 12v doesn't seem really far out for that scenario, does it?

Just a few minutes ago I did go out and measure the voltage at the device, as suggested by scalf77, and confirmed that the 12.0 vdc that showed on my "cheesy battery tester" was accurate by my fluke multi-meter.

Under normal conditions I can park and use the refer, lights and play DVD's on my 18" monitor on the house battery for about 2 days before I need to think about running the engine or plugging in, etc.

Does this seem like a weak soldier; do I really have to worry about the "mortality" of my battery?

[rallypanam]

Either way, your battery may be your issue..

You shouldn't let your battery (unless lithium-ion) get below about 50% charge, which is roughly 12.2V. If you have, my mortal wound comment may apply:



And, as Scalf mentioned, if your battery is nearly dead, and the fridge or any other load kicks on, the voltage could easily drop below the minimum for the alarm, setting it off.

[Scalf77]

While discharging to to 11.9 or 11.7 on a regular basis won't necessarily kill your battery, it will certainly make it's lifespan much shorter. The chart below shows the relationship of depth of charge to battery cycles



The standard rule of thumb is to not discharge below 50% as this is a good balance between bank size and longevity, it also gives you a little room to push it on occasion as needed.
A good battery FAQ located here Deep Cycle Battery FAQ

-greg

[skyrat]

Great article on everything batteries, thanks! Just read the whole thing. Super interesting.

The chart in the "State of Charge" area seemed the most pertinent to this discussion and simplest to understand.

The copy read.
"For longest life, batteries should stay in the green zone. Occasional dips into the yellow are not harmful, but continual discharges to those levels will shorten battery life considerably."

The green zone was as follows.
80%=12.42v, 70%=12.32v, 60%=12.20v, 50%=12.06v, 40%=11.9v