[RE-wrenches] battery venting

Sat Dec 31 22:03:20 PST 2011

So, is it best to use a DC fan or an AC fan? Should I run it on a relay, or just run it all the time? What conditions would a relay be set to: whenever the battery is at the absorption voltage or higher? A small 12V fan (which may or may not be brushless) wouldn't be a big power draw, but I'm worried something larger would be a bad parasitic load if run all the time. Would the main thing that it be near the diameter of the vent pipe?

Also: does anyone have a rule of thumb for the maximum angle of the vent pipe from plumb? 45˚? 60˚?

Thanks,
Jeffrey Quackenbush
NABCEP Certified PV Installer
Peripatetic Solar Technician

________________________________
 From: bob ellison <reellison at gmail.com>
To: 'RE-wrenches' <re-wrenches at lists.re-wrenches.org> 
Sent: Sunday, January 1, 2012 5:06 AM
Subject: Re: [RE-wrenches] battery venting

Mount a BRUSHLESS fan inside the box blowing out into the pipe, do not
pressurize the box, that will blow gasses into the room, it is bound to
leak. Use screened vents to keep out the critters.
I use a Carlon 6x6x4 box to mount the fan and vent, also don't mount the
relay if you use one, in the battery box. Things night go bang!

Going back to the woods!

Happy New Year!
Later,
Bob 

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Exeltech
Sent: Saturday, December 31, 2011 5:17 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] battery venting

Hello Jeffrey,

Since you're working under constrained conditions for the install, and
apparently have little option on using the flooded/vented batteries, here
are some suggestions that may help:

1) Do your best to ensure the battery enclosure is reasonably sealed except
for the outlet vent.

2) Use non-corrosive vent pipe of as large a diameter as is practicable for
your circumstances.
Angle it upwards at all times.  A 4% hydrogen concentration can be
explosive.

3) Install corrosion-resistant screening at the vent outlet, and with the
vent oriented in a manner to discourage entry of unwanted anything.

4) Install the vent fan on the fresh-air inlet side of the box.  The inlet
itself should be located below the tops of the batteries, and at the
opposite end from the vent.  Screen the inlet to keep critters and anything
else from getting in.

This accomplishes several goals:

a) Keeps the fan and its mechanics out of the corrosive flow; b) Eliminates
any possibility of a spark occurring in the hydrogen; c) Locates the fan
into a "friendlier" atmosphere, reducing its exposure to insects and other
accumulating junk;
d) Makes the fan easier to service/replace if it
*should* fail.

Happy New Year to all.

Dan

> --- On Sat, 12/31/11, Richard L Ratico <Richard.L.Ratico at VALLEY.NET> 
> wrote:
> 
> From: Richard L Ratico <Richard.L.Ratico at VALLEY.NET>
> Subject: Re: [RE-wrenches] battery venting
> To: re-wrenches at lists.re-wrenches.org
> Date: Saturday, December 31, 2011, 1:47 PM Huh??? I'm probably 
> missiing something here.
> What happens when the powervent fails???
> I replace it with another, the same thing I do when other equipment in 
> our whiz bang industry fails.
> 
> The difference with the powervent is that it is easy and relatively 
> inexpensive. I've also had good luck using screens on the vent inlet 
> and outlets, per the instuctions, albeit a high tech solution.  :-)
> 
> Seems inverters, charge controllers,
> batteries, DC breakers, even modules fail more frequenty.
> Rant off.
> 
> Dick Ratico
> Solarwind Electric
> 
> 
> 
> --- You wrote:
> Jeffrey,
> 
> I'll second Jay's suggestion that sealed AGM batteries are the best  
> choice in this circumstance. Presumably this is a grid backup system 
> so the poor endurance of AGMs for cycling applications shouldn't be an 
> issue. If you use a Zephyr power vent horizontal runs shouldn't be 
> problem, but what happens when the power vent fails?
> It will fail. I've seen the bearings wear out on one and another that 
> failed when insects got into the blades and gummed it up to the point 
> that the motor stalled.
> 
> Kent Osterberg
> Blue Mountain Solar, Inc.
> www.bluemountainsolar.com
> t: 541-568-4882
> 
> 
> On 12/31/2011 6:59 AM, JRQ wrote:
> > Wrenches,
> >
> > I'm looking at a potential battery backup system wtih a 200 AH @48V 
> > flooded battery bank in the basement electrical room of a 3 story 
> > building.
> > There is a window in the electrical room. The batteries will be 
> > located about 10' from an outdoor wall. The building is all 
> > reinforced concrete, so I can not run a vent pipe vertically from 
> > the  batteries. Does anyone have a rule of thumb for how much the 
> > vent pipes can be angled from the batteries? Would it be more 
> > lenient for short sections of pipe (say <2') versus one long angled 
> > piece from the batteries? My instinct would be to keep the pipe no 
> > more than 45? from plumb.
> >
> > Or with bending the vent pipe: does anyone have a best-practice rule 
> > for the sum of the angles of bends?
> >
> > Thanks,
> > Jeffrey Quackenbush
> > NABCEP Certified PV Installer
> > Peripatetic Solar Technician

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