More Kohler RES controller stuff [RE-wrenches]

Dean T. Newberry deant at dcn.org
Wed Dec 1 21:06:08 PST 2004


 

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Hi Allan,
On telecom switching center DC Systems we had power ventilation hoods on=20
the battery banks.
When charging any lead acid batteries etc, there is always gassing, ie=20
hydrogen and oxygen mixing above the battery. Any loose connection near=20
the gas can cause a spark when a load is applied. The bad connection=20
could be internal to the battery, or the post to clamp, or loose or=20
corroded wire in the clamp, or possibly the start switch itself if nearby.
I induced a nice fireball when cleaning and regreasing the connections=20
on a 120VDC battery bank. My knife accidently arced across the 3" 120V=20
gap.The resulting explosion above the battery was harmless because it=20
was contained in a fume hood, and didn't get down into the battery case=20
because the battery had a flame protection vent. However if the battery=20
is in a chassis or the burn gets down into the head space above the acid=20
line the resulting compression will be harmful.
An oxygen fuel mixture burns much faster than an air fuel mixture. A=20
harmless demonstration that approximates the effect of Oxy and Hydrogen=20
above a battery is to put a pebble 1/2" or so in a ziploc sandwich bag=20
and fill it with propane or acetelyne from your torch and toss it onto a=20
burning newspaper. Do this on the driveway or another open place. The=20
bag will just burn up a bit faster than if it had air in it a real dud.=20
Try this with the oxygen, and still no big deal. Put in earplugs, wear=20
safety glasses and mix oxy and acetelyne or propane and try it. If you=20
are alert you can see the flame front pass you, a bright spherical=20
bubble out to about 10 feet diameter, and your neighbors for more than a=20
mile will be real impressed. The newspaper will blow out, and the pebble=20
will be just about where it landed. I could find no evidence of the=20
ziploc. Any attempt to constrain the burn with a battery case or=20
generator chassis will send bits of stuff flying at a great rate.
Your customer will recover most of her hearing within a week. I have a=20
pretty good case of tinnitis from the military and construction, so I=20
can't tell if the harmless demonstration had a long lasting effect on my=20
hearing, but I remain very respectful of battery gas.
Battery banks should be installed in a clean, well lighted, ventilated=20
space, the following is the code section on Batteries, in my experience=20
all of these requirements make good sense.
--------------------------------------------------------------------------
ARTICLE 480
Storage Batteries


480.9 Battery Locations. Battery locations shall conform
to 480.9(A), (B) and (C).

(A) Ventilation. Provisions shall be made for sufficient
diffusion and ventilation of the gases from the battery to
prevent the accumulation of an explosive mixture.

(B) Live Parts. Guarding of live parts shall comply with
110.27.

(C) Working Space. Working space about the battery systems
shall comply with 110.26. Working clearance shall be
measured from the edge of the battery rack.


480.10 Vents

(A) Vented Cells. Each vented cell shall be equipped with
a flame arrester that is designed to prevent destruction of
the cell due to ignition of gases within the cell by an external
spark or flame under normal operating conditions.

(B) Sealed Cells. Sealed battery or cells shall be equipped
with a pressure-release vent to prevent excessive accumulation
of gas pressure, or the battery or cell shall be designed
to prevent scatter of cell parts in event of a cell
explosion.


503.14 Storage Battery Charging Equipment =97 Class
III, Divisions 1 and 2. Storage battery charging equipment
shall be located in separate rooms built or lined with substantial
noncombustible materials. The rooms shall be constructed
to prevent the entrance of ignitible amounts of
flyings or lint and shall be well ventilated.


VIII. Storage Batteries
690.71 Installation.

(A) General. Storage batteries in a solar photovoltaic system
shall be installed in accordance with the provisions of
Article 480. The interconnected battery cells shall be considered
grounded where the photovoltaic power source is
installed in accordance with 690.41.

(B) Dwellings

(1) Operating Voltage. Storage batteries for dwellings
shall have the cells connected so as to operate at less than
50 volts, nominal.
Exception: Where live parts are not accessible during routine
battery maintenance, a battery system voltage in accordance
with 690.7 shall be permitted.

(2) Guarding of Live Parts. Live parts of battery systems
for dwellings shall be guarded to prevent accidental contact
by persons or objects, regardless of voltage or battery type.
FPN: Batteries in solar photovoltaic systems are subject to
extensive charge=ADdischarge cycles and typically require frequent
maintenance, such as checking electrolyte and cleaning
connections.

(C) Current Limiting. A listed, current-limiting, overcurrent
device shall be installed in each circuit adjacent to the
batteries where the available short-circuit current from a
battery or battery bank exceeds the interrupting or withstand
ratings of other equipment in that circuit. The installation
of current-limiting fuses shall comply with 690.16.

(D) Battery Nonconductive Cases and Conductive
Racks. Flooded, vented, lead-acid batteries with more than
twenty-four 2-volt cells connected in series (48 volts, nominal)
shall not use conductive cases or shall not be installed
in conductive cases. Conductive racks used to support the
nonconductive cases shall be permitted where no rack material
is located within 150 mm (6 in.) of the tops of the
nonconductive cases.
This requirement shall not apply to any type of valveregulated
lead-acid (VRLA) battery or any other types of
sealed batteries that may require steel cases for proper operation.
--------------------------------------------------------------------------
Obvioulsy there is more on battery installation, but these are the=20
relevant sections re the subject venting and explosion.

cul deant

Allan Sindelar wrote:

>=20
>
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>We have one customer who also has an Onan RV generator, with no charging
>circuit on the starting battery. She has had battery problems, and had=
 been
>using an automotive charger to keep the battery charged. Recently I added=
 an
>AC receptacle on the gennie output to allow the charger to run when the
>gennie is charging. Now I'm concerned: I measured no no-load draw with=
 this
>gennie at rest, and figured her starting problems were eventual failure of
>the starting battery from lack of charging. What draw have you measured,=
 and
>is there something more I should know about this unit?
>
>On a related note, several weeks ago this client went to start this gennie
>after having run her automotive charger (Shumaker homeowner-grade 10A
>automotive charger) for several hours off of system (inverter AC) power.
>When she hit the start button the battery exploded. The battery was under
>the generator and that protected her from acid, but her hearing is still
>partially gone. We weren't there, and she couldn't explain in detail what
>happened. It concerns me, as I can't explain why this battery exploded.
>
>
>----- Original Message -----=20
>From: "Kurt Nelson" <sunwise at cheqnet.net>
>
>Greetings -- I've got a customer with an Onan Emerald, a generator that
>was apparently designed to ride along on a big RV and get starter
>battery charging from the engine alternator.  He's had lots of problems
>with it including head gasket, but we had fairly good results keeping
>it's battery charged with a slightly larger array at the generator shed
>(200 watts) charging that starter battery.  But, that array also
>transfers to the house system to complement the 1,200 watts there when
>the starter battery is satisfied.  The 200 watts is enough to keep the
>gen-set happy during cloudy weather and is not wasted during sunny
>periods by the transfer circuitry.
>
>
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>

--=20
Dean T. Newberry
Marketing and Sales

Quantum Energy Group
256 Applegate School Road
Applegate, Ca. 95703

Tel: 530 878-4585
Fax: 530 878-6685
Cel: 530 867-2392

deant at dcn.org
http://www.talbottsolar.com/
http://mjdsolar.com/

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