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My approach isn't scientific, but my own common-sense attempt to
balance competing objectives, as William has identified. I
more-or-less address this in the current HP batteries article. To
me, insulating a battery box does little good in an otherwise cold
ambient environment. Batteries don't generate enough heat from the
charging process to overcome cold ambient (especially winter outdoor
in our cold climate) temperatures. I'd rather see the battery box
located in a tempered space. Indoors is good, but not necessary.
Indoors is unlikely to get and stay above about 75 degrees for long
enough (in our climate) to allow massive batteries to rise above
their stated ideal of 77F. But a separate tempered space - that is,
an insulated space that adheres to good basic passive solar
guidelines: glazing for warmth, overhangs for summer, mass (floor or
trombe wall) for storage - is nearly ideal. The batteries have their
own substantial thermal mass, so average seasonal ambient
temperatures of 50-75F are pretty close to ideal. With enough mass
in the larger space, the venting necessary to exhaust hydrogen
doesn't have much effect. I'll use a 12V Power Vent or two, each
controlled by an MX60/FM60/similar Vent Fan option on the auxiliary.
These combine a voltage-actuated switch function with hysteresis and
intermittent fan operation, so not much heat is lost.<br>
<br>
But hey, that's ideal, and means that I have some control of the
entire building process. That's a rare and quite yummy occurrence.
But it makes a great ideal to explain to the customer; then we do
the best we can with what situation and budget will allow.<br>
<br>
Here we're more concerned about cold winter temperatures than summer
overheating. I have historically taken the position that locating
batteries indoors is a good thing, as long as the box is very
carefully sealed and vented. I'm big on Zephyr Power Vents,
especially because when correctly vertically mounted, they have a
built-in backdraft damper, essential in an indoor space with a wood
stove or similar. So far, in twenty years I haven't yet had an
accident or close call that resulted from locating batteries
indoors.<br>
<br>
Hope that this helps a bit,<br>
Allan<br>
<br>
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<p class="MsoNormal" style=""><span class="il"><b style="">Allan</b></span><b
style=""> Sindelar</b><span style="font-size: 10pt;"><br>
<a href="mailto:Allan@positiveenergysolar.com"
target="_blank"><span class="il">Allan</span>@positiveenergysolar.com</a><br>
NABCEP Certified Photovoltaic Installer<br>
EE98J Journeyman Electrician<br>
<b style="">Positive Energy, Inc.</b><br>
3201 Calle Marie<br>
Santa Fe, New Mexico 87507<br>
<b style="">505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/"
target="_blank">www.positiveenergysolar.com</a></span></p>
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<br>
On 12/11/2010 4:45 PM, William Miller wrote:
<blockquote
cite="mid:6.0.1.1.2.20101211154202.032279a8@millersolar.com"
type="cite">
<font size="3">Friends:<br>
<br>
I'm a little addled because of a flu. Allow me to resend the
post
below with a more sensible wording:<br>
<br>
I'm not sure how you insulate a space and at the same time vent
it.
Any insulation is pointless if you have a draft flowing through
the
area.<br>
<br>
If you are to insulate, then you must have an active venting
system that
can open and commence venting promptly and reliably at the first
possibility of hydrogen gas emission.<br>
<br>
Being from a temperate climate, this has not ben an issue for
me, but for
those of you in more extreme climates, how do you handle this
conundrum? Electric blowers with louvers?<br>
<br>
William Miller<br>
<br>
<br>
At 02:10 PM 12/11/2010, you wrote:<br>
</font>
<blockquote type="cite" class="cite" cite=""><font size="3">At
08:25 -0800 11/12/10, Joel
Davidson wrote:<br>
</font>
<blockquote type="cite" class="cite" cite=""><font size="2">I
recommend
insulation. In general, operating temperature is very
important.
Batteries last longer if kept cool. However, a battery below
60 degrees F
(15.5 C) has reduced capacity. Temperatures above 77 F (25
C) increase
capacity only slightly but they significantly reduce battery
life.
Batteries operating regularly above 85 F (29.4 C) lose have
their
operating life.<br>
Joel Davidson</font></blockquote>
<font size="3"><br>
OK so you recommend insulation to keep them cool? For me,
insulation is more likely to result in higher temperatures in
summer. In winter, an insulated space is obviously ideal for
performance depending on the kind of winter (which seems to be
a variable
these days). In summer, insulation directly on the battery
seems
unlikely to keep them cool. On charge they will definitely
need a
temperature sensor and will be likely to get hotter than
ambient if
insulated.<br>
<br>
<br>
</font>
<pre>--
</pre>
Hugh
Piggott</blockquote>
<pre wrap="">
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