I was hesitant to reply because I surely will look foolish, but perhaps it may
help someone in the future. I did something very stupid back in 2001 that
caused an explosion.
The battery bank (12 volt, 660AH) was located in a metal cargo container next
to the wall and set in a plastic container. The container had open doors on
both ends. The battery was in the absorption cycle with heavy gassing. I
noticed that the positive terminal was slightly loose. Fully aware of the
danger of the task I was performing, I grabbed my socket wrench and began to
carefully snug it down. Even though I carefully observed the location of the
wrench, I did not think about the steel container wall as having a path back to
battery negative. It did. I blew the top off a battery that I was standing
over. Fortunately I was wearing safety glasses or I probably would not be here
today typing this. There was a water hydrant near and I was able to flood my
face and body for about 15 minutes. No facial scares but a lessen very well
learned: Do NOT work on batteries that are off gassing. Gassing begins at about
2.3 volts per cell. If you are a battery novice, I encourage you to thoroughly
educate yourself and do not neglect your safety gear when working on batteries.
Another event I witnessed: In 2007 I was at a campground and heard an
explosion. The owner of an RV a few spaces down from me was opening the battery
compartment as I walked up. Inside he had un-vented batteries in the same
compartment as the inverter and other switch gear. His batteries were obviously
gassing when something sparked it off. The top was blown off a 6 volt battery
and he had electrolyte everywhere and a damaged cargo door. We work on hundreds
of RV's and sadly I see this kind of poor "workmanship" every week at our
service center.
Larry Crutcher
Starlight Solar Power Systems
928-342-9103
----- Original Message -----
From: Kent Osterberg
To: RE-wrenches
Sent: Wednesday, December 15, 2010 10:21 AM
Subject: Re: [RE-wrenches] Battery based hydrogen incidents
Sounds like, in general, that the off-grid industry has been fortunate to not
have hydrogen explosions. That's good. No explosions here either. But one
shouldn't take that as evidence that it couldn't happen. I don't believe this
is a circumstance where it is better to be lucky than good. That's why I
recommend doing the calculations.
Kent Osterberg
Blue Mountain Solar
Dana wrote:
Ken -
To meet the flow have run 2 and 3 fans to meet the flow. 2" output from the
fan into a 4" header with a matching 2.5" inlet as far away on the lowest
portion of the battery box.
In 22+ years in off grid installations I have yet to see or even hear of
one hydrogen explosion. I get repeatedly asked why we have to go to the efforts
we go to for box and venting. I am not able to provide even one incident that I
have heard rumor of.
Q - How many battery based hydrogen incidents have happened in our
collective experience?
Dana Orzel
Great Solar Works, Inc
E - [email protected]
V - 970.626.5253
F - 970.626.4140
C - 970.209.4076
web - www.solarwork.com
"Responsible Technologies for Responsible People since 1988"
Do not ever belive anything, but seriously trust through action.
From: [email protected]
[mailto:[email protected]] On Behalf Of Kent Osterberg
Sent: Tuesday, December 14, 2010 12:07 PM
To: Wrenches
Subject: [RE-wrenches] Battery Venting
Fellow Wrenches,
The discussion about battery venting reminds me of a useful and inexpensive
program, BattMV, for determining ventilation requirements per EN-50272.
EN-50272 is a European standard used to determine how much air flow is needed
for a room, I don't know of a equivalent standard used in the U.S. It takes a
surprising amount of ventilation. For a 400-AH 48-volt L16 bank charged at
57.6 volts and 24 amps, it's about 7 CFM just to keep the %H2 down to 4%. A
12-volt Zephyr vent is good for about 5 CFM! If you think you are venting
enough, take some time and study this issue.
Kent Osterberg
Blue Mountain Solar
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