Carbon monoxide detectors and hot batteries? [RE-wrenches]

John Raynes john at raynes.com
Wed May 23 08:19:07 PDT 2007


<x-flowed>

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


- - - -
Hosted by Home Power magazine

To send a message: RE-wrenches at topica.com

Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php

Check out participant bios: www.mrsharkey.com/wrenches/

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael_welch at sbcglobal.net

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

For Topica's complete suite of email marketing solutions visit:
http://www.topica.com/?p=TEXFOOTER
--^----------------------------------------------------------------




</x-flowed>



More information about the RE-wrenches mailing list