>That is why there was a gap between putting the new battery in and putting
>the battery in a box. I didn't think there was a problem but then an A&P
>came to look over my plane for possible buying, he said that it was
>dangerous not to have a box. A&P, IA's are the experts.
>>Batteries have been known to explode so I would recommend some kind of
>>secondary containment for safety regardless if it is an RG, flooded cell or
>>whatever.
Battery boxes have NEVER been designed to contain an exploding
battery . . . in fact, battery boxes have been DEMONSTRATED
to make an explosion more likely if not more violent.
Real life case in point:
Amateur built airplane, all composite, very nice composite
battery box glassed right into the passenger seat back.
Alternator goes into OV. No annunciation of OV condition
and battery begins to outgas. In the course of "troublshooting"
the system, a few switches get thrown, one of which is
the battery master contactor control switch. Battery contactor
INSIDE the box with the battery ignites ideal mixture and
blows up battery box.
No flight-safety damage to aircraft but the pilot's underwear
was seriously compromised.
What's the physics of this event? To have an explosion you
must have three conditions. (1) A source of FUEL that's mixed
in proportions to produce rapid combustion. Too much fuel/
oxygen, no explosion; too little fuel/oxygen, no explosion.
Cook a battery and you disassociate water H20 into H2 and
O2 in ratios ideal for recombination in spectacular manner.
(2) CONTAINMENT in this case was the nicely crafted battery
box. Without containment, gunpowder simply burns. Wrap it
up in rolls of newspaper and you have a firecracker. Finally,
(3) IGNITION provided by the battery contactor located inside
the battery box.
LOTS of things could be done to break the chain of events
that could have been much more serious . . .
(1) Proper ov protection on the airplane's electrical system.
(2) No battery box . . . let the vented gasses waft away
in the breeze.
(3) Don't mount electrical equipment inside the battery box
along with the battery.
(4) Adequate instrumentation on the electrical system to
KNOW what's happening when stuff starts to misbehave and
adequate UDERSTANDING of the system to do the right things
about it.
By the way, the BIG guys don't have battery boxes either.
The battery on a bizjet comes with a nice connector on the
side. You drop the critter into a tray, strap it down
and plug it in. None the less, there are documented cases
of an RG battery blowing up when a poorly welded inter-cell
connector burned off . . . needless to say, a redesign and
modification to the assembly process was accomplished in
a hurry.
Not one government-approved airplane-banger in ten
understands or can explain what you've just read.
Bob . . .
--------------------------------------------
( Knowing about a thing is different than )
( understanding it. One can know a lot )
( and still understand nothing. )
( C.F. Kettering )
--------------------------------------------
http://www.aeroelectric.com
|