Carbon monoxide detectors and hot batteries? [RE-wrenches]
Phil Undercuffler
p.undercuffler at conergy.us
Wed May 23 08:50:37 PDT 2007
As both a solar geek, off-gridder and volunteer firefighter, this is an
issue that caught my attention some years ago. It seems many
residential CO monitors cannot tell the difference between CO and
Hydrogen.
I found this out the, well, interesting way, when my CO monitor started
triggering in the summer when my heating system (the only possible
source of CO) was turned off. I was told at the time that the detector
was sensing the hydrogen coming off my batteries, and triggering the
alarm.
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Please note new phone extension!
Phil Undercuffler
Technical Services Manager
Conergy, Inc.
1730 Camino Carlos Rey Suite 103
Santa Fe NM 87507 USA
Office | 505.473.3800 x4841
Fax | 505.473.3830
www.conergy.us
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-----Original Message-----
From: John Raynes [mailto:john at raynes.com]
Sent: Wednesday, May 23, 2007 9:19 AM
To: RE-wrenches at topica.com
Subject: Re: Carbon monoxide detectors and hot batteries? [RE-wrenches]
Geoff,
Don't assume that the CO detector was actually responding to CO.
Having worked in the electrochemical sensor business for a few years in
an earlier life, I became aware of the problem of designing a gas
sensor that is selective only to the target gas. With industrial
sensors, the response of the sensor to interference gases is usually
well specified, so that the potential end user can evaluate their site
for the potential presence of the interfering gases. Sensors that are
highly selective to only the target gas can often command a hefty
premium.
I'm not versed in the specifics of the residential mass produced CO
detectors, but I would almost expect that to get the cost down, those
sensors are susceptible to at least some interference gases, and that
they're still approved for home use due to the highly improbable
presence of those gases in non-industrial environments. And in any
event, the error is on the safe side, as you found out.
I have no way of knowing if CO can be present in highly reactive LA
cells, the battery experts will have to comment on that. I'm just
offering an explanation if it turns out that the batteries don't look
to be a source.
In my experiences with failing battery banks, spotting the failed cell
is usually quite obvious, when it gets to the point that things are
cooking away. The failed battery will likely read in the range of 5 to
5.5 volts while still connected to the bank, and all of the other
strings in that bank will read higher, as they are reacting to the
higher current flowing into the string to feed the shorted cell. Once
you disconnect the string with the failing cell, the bad battery
usually will immediately fall to 4 volts and some change.
John Raynes
RE Solar
Torrey, Utah
At 10:53 AM 5/22/2007 -0400, you wrote:
Hello all wrenchies -
I VERY concerned customer called with what seems to be a failing battery
bank (tons of heat, bubbling way more than normal, and a recently
manifesting large difference between strings of water consumption).
These
are T-105s retired from an electric vehicle, and I suspect an open or
shorted cell.
He is remote and has transferred AC loads and shut things down on the DC
side... and once he borrows a multimeter I will walk him through a
resistance check on the cells and suspect to find a bad battery. Along
with
looking for anomalous individual battery voltage, at rest and during
heavy
charging do any of you have any other quick tests to suggest? I already
asked if he had an infrared thermometer... and when I spoke with him
"all
the batteries were too hot to touch".
So - the gist of my post is: he was alerted to this situation not by
collapsing voltage under load, but by his CO detector going off. What
chemically is happening there? These are flooded LA batts... is
insulation
and plastic heating up and generating CO? Does the CO detector pick up
other stuff?
The batteries are in a roomy painted plywood box with plastic liner,
screened low vents and a 2" pvc power vented to the screened exterior (I
should have him check that for wasp nests). Will check to see if the
vent
operates. it was controlled by the MX-60 aux to come on at around 53
VDC.
For a brighter energy future,
Geoff Greenfield
President
Third Sun Solar & Wind Power Ltd.
340 West State street, Unit 25
Athens, Ohio 45701
(740) 597-3111 fax: (740)597-1548
www.third-sun.com
Clean Energy - Expertly Installed
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