Drake,
My suggestion is that to achieve the client's wishes as well as
your own cooling concerns, you include a Zephyr Power Vent in a 2"
PVC vent stack to the outside. Let the charge controller's
voltage-actuated auxiliary setting power the vent (it's OK to do
so directly on Outback and Midnite controllers, and I believe all
other major ones as well). As these are sealed batteries,they
won't gas significantly under normal charge voltages. Set the
turn-on voltage at the gassing voltage, or thereabouts depending
on your determination. This will be above (or below but near)
normal charge voltage, and will cause the Power Vent to turn on
only under abnormal conditions. The Power Vent also has a
backdraft damper built in (which is why it must be oriented
vertically) so will prevent excessive convective heat loss when
not running.
This won't address the possibility of one cell failing and
gassing, as the string voltage determines turn-on. However, as
others have pointed out, that may be of benefit: if one cell fails
you'll still be able to smell it and address the problem.
Allan
Allan Sindelar
al...@sindelarsolar.com
NABCEP Certified PV
Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy,
Inc.
505 780-2738 cell
On 10/29/2014 6:19 PM, Drake wrote:
Hi Daniel,
I typically vent them the way you do, which will allow any small
amount of hydrogen out. The customer is absolutely adamant about
venting these to the outside. I will cooperate so long as his
method doesn't compromise the system through cooling the batteries
unnecessarily in the dead of winter.
He is a lawyer and came to the conclusion of the need for venting
to the outside from reading the NEC which says that sealed
batteries "require the same amount of ventilation" as liquid lead
acid batteries. The code also says to vent appropriate to battery
technology, so the code says two conflicting things. On the other
hand, it doesn't say that liquid electrolyte batteries need to be
vented to the outside. They will sure stink if you vent them to
the inside.
Drake
At 09:54 AM 10/29/2014, you wrote:
I just re-read the original post Drake.
These are AGM batteries. Do you have
a "belt, suspenders,...then a rocket pack" type of client here?
We typically vent our AGM boxes with small louver vents top and
bottom to
allow the batteries to ventilate for cooling purposes, not H2
concerns.
With Regards,
Daniel Young,
NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90
NABCEP Certified Solar Heating InstallerTM: Cert #SH031409-13
-----Original Message-----
From: RE-wrenches
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On
Behalf Of Ray Walters
Sent: Tuesday, October 28, 2014 11:12 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Passive Battery Venting
That's why we usually have the batteries in a garage, basement,
or out
building that is not open to the living space.
I've seen some cases of very well sealed and insulated
enclosures allowing
batteries to over heat, and also build up a lot of acid damaged
connections.
Boxes I've seen with more air space and less sealing don't get
this build
up, but you're correct: they do occasionally allow H2S into the
surrounding
area.
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 10/28/2014 8:10 PM, Jerry Shafer wrote:
>
> We do what we can to seal the enclosure so if or when a
battery fails
> and really gasses off the two vents on the same wall
regardless of
> wind direction will vent the gas. If it is not sealed then
the gas can
> travel through out the area this is not advised.
>
>
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