[RE-wrenches] Battery Off Gassing and CO Detectors

Fri Feb 3 14:32:01 PST 2012

We use plywood boxes with sloped top as well, I like the sloped top not only to help migrate the gasses but also because of the fact that a flat surface usually collects stuff! We use soffit vents at the bottom of the box and Zephyr vents to evacuate the enclosure but if the vent fails all there is to evacuate the box is a small hole on the side of the vent.  I like the idea of having a small passive vent in addition to the Zep fans as an added precaution. I wouldn’t rely on a CO detector to detect hydrogen, it was a yet another learning for me, but it does seem like it could help alert the customer of an issue with venting.  We have customers that leave their off grid homes for over a week due to their jobs so we need to have the battery bank charging and venting be as robust as it can be since humans are not always around to make the decisions to start the generator to charge or to note that the vent is not working. 

Rich

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Dana
Sent: Friday, February 03, 2012 11:43 AM
To: 'RE-wrenches'
Subject: [RE-wrenches] Battery Off Gassing and CO Detectors

I am a firm believer in visual inspection the battery bank prior to opening the top weather there is an issue or just looking.

We use plywood boxes, sloping top, caulked top frame, top is ¼” Plexiglas /  edged with flat edged aluminum storm window frame to provide stability to screw down on the edge and keep the Plexiglas from cracking while securing down.  Top is not cheap but  it is clear, resists outgasing, long life, light, & hopefully will keep a client from stacking stuff on top of the battery bank esp. if sloped.

There are several extrusion options so look before you order it as to the function of having a flat to attach closed cell foam and running screws through it. 

Then we apply a closed cell foam gasket to the aluminum top frame not the wood box. Seems to last much better than attaching the foam to the box itself.

Bottom is lined with EDPM [pond liner] available at most irrigation and underground pipe wholesales. Lay it flat and fold it up and secure to interior.

Also 2” screened bird vent inlet low [almost floor level] at the diagonal opposite corner of the box from the vent fan exit point.

Dana Orzel

Great Solar Works, Inc

E - dana at solarwork.com

V - 970.626.5253

F - 970.626.4140

C - 970.209.4076

web - www.solarwork.com

"Responsible Technologies for Responsible People since 1988"

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of john
Sent: Friday, February 03, 2012 9:23 AM
To: re-wrenches at lists.re-wrenches.org
Subject: Re: [RE-wrenches] wrenches] Battery Off Gassing and CO Detectors

Rich,

   I have found that having the CO detector anywhere nearby seems to pick up the battery gasses.  I had a problem with one customer's battery box (built by their carpenter) made of pine boards tightly fitted together. It was leaking gasses thru the crack between the boards on the top near the vent.  I put electrical tape on the crack and the problem was solved.  The vent fan was working fine but did not have enough volume to keep the gasses from escaping upward and out of the crack. A good reason to use plywood or something else other than multiple boards.  I would definitely agree with Bob that the CO monitor does work to indicate a bad fan.   I have had them go off when the voltage set point on the dux relay was set too high to catch the early stages of gassing.

John

CVSolar

-----Original Message-----
From: Rich Nicol <rich at solartechvt.com>
To: 'RE-wrenches' <re-wrenches at lists.re-wrenches.org>
Sent: Thu, Feb 2, 2012 9:40 pm
Subject: [RE-wrenches] Battery Off Gassing and CO Detectors

Wrenches

I understand that battery gassing of Hydrogen Sulfide can set off CO detectors.  A new customer who I am about to replace a large battery bank for had his furnace tech on site today to check for proper operation of the furnace since his CO detector was going off, the tech found the high levels of CO were coming from the battery bank. I recognize its not actually CO but rather it’s hydrogen sulfide since his generator had recently been running to charge the batteries and I assume that the detector couldn’t differentiate the Hydrogen Sulfide from the carbon monoxide. Does anyone have any insight into the mechanism that CO detectors use to detect the gas and secondly could they be used reliably to detect battery gassing that isn’t being evacuated from the battery enclosure such as when a power vent fails? Maybe a CO detector could be located near enough to the vent hole in the Zephyr fan to detect high levels of Hydrogen Sulfide that aren’t being pushed out when the fan fails to operate and open its damper? Power vent failure is a fear that a number of customers have expressed, maybe this could be  a method of alerting the homeowner that there is an issue.

Thanks

Rich

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