(Editor’s note: In my job at
Kennedy Space Center, many techs
tell me they still prefer the Simpson
analog meter to any of the digital
ones. The visual indication of “open”
vs. “continuity” or “voltage” vs.
“dead” is so obvious. The needle
swings or it doesn’t. Plus, any meter
that is still ticking after 30+ years of
use and abuse has to have
something right about it!)
since the screen is backlit; also is
clear as can be in the sun.”
In conclusion, a lot of any tool
choice depends on what you’re
using it for. Quickie, low resolution
checks? High precision
troubleshooting? Professional or
hobby? The answers above reflect a
wide range of needs and solutions.
Doing your research — as this poster
did — is always going to be best.
“In the area of budget-minded
meters, I’ve had several of the
Harbor Freight brand and most have
been just fine. Those are the ones I
keep around as “loan outs” in the
pits. They get the job done and if
they disappear it was only $20.
(Editor’s note: I just looked, and they
have them for $3.49!) The biggest
difference between the Fluke and
the cheapies is the resolution speed.
The Fluke reacts almost as fast as an
analog meter. Some of the cheaper
units update the screen like only
every half second.”
LiPoly Battery Fires
Harbor Freight
“My favorites are Fluke and
Triplett. I’ve had my Fluke 29 series 2
for over 20 years now. It’s even
survived a fire in the
shop. The case is a bit
scorched but it still works
perfectly!”
“We use the
Milwaukee digital
multimeter 2217-20 at
my work and I really like
them; they are tough
little buggers too. The
white on black readout
works well in the dark
Many combat bots and, of course, many other R/C hobby
devices use Lithium Polymer
batteries due to their incredible
energy density. This allows lots of
power to be packed into a very
small, lightweight package.
Unfortunately, these batteries
can sometimes catch fire with
spectacular results. There are lots of
guidelines and opinions about how
to design LiPoly batteries into your
bot. What to do if they catch fire is
not always quite so clear.
A recent conversation among
builders and event organizers yielded
some great data. All this information
has been validated through
Material Safety Data Sheets
and the National Fire
Protection Association’s
website.
It’s pretty universally
acknowledged that the
only “official” fire fighting
tool is a class D fire
extinguisher, specially made
for fires like lithium and
magnesium. Most venues
don’t provide these, as the
Milwaukee Tools
dry powder is quite messy and not
gentle on carpets, drapes, other
bots, etc.
CO2 extinguishers, commonly
available, at best do nothing.
Many sources feel the CO2 actually
reacts with burning LiPoly
batteries, causing more problems
than they help.
Many EOs provide buckets of
sand or salt. Burying a small battery
in either of these is an approved
method — per MSDS — for
containing a battery fire. Use two
metal buckets, both with sand/salt
in them. A pair of heavy welding
gloves and a pair of cutters should
be stationed with the buckets. If
safely possible, the gloves can be
used to transfer the battery into one
bucket, then the contents of the
other dumped on top. The entire
bucket then goes outside the venue,
following a pre-planned and pre-briefed egress route.
A specific substance for fighting
these fires is copper powder, but
let’s face it. No one is going to have
that lying around!
Many folks feel that salt
water can be used to safely put
out a burning LiPoly. Many safety
organizations disagree with this.
A LiPoly that is damaged or
needs to be disposed of for some
other reason can be soaked in salt
water for several days to neutralize
the chemistry. But, dumping a
burning lithium battery in water —
even salt water — is not
recommended.
An interesting input from one
builder: “You can get a five gallon
bucket of the class D powder at a
fire rescue supply shop. This can be
used in place of salt or sand, and is
much cheaper than getting a fire
extinguisher refilled. It also is a lot
less messy if you can get the battery
out of the bot.”
All EOs agreed that it’s a
partnership between the venue,
organizer, and builder to make sure
everyone knows what to do in case
of a battery fire, and to follow the
pre-briefed plan. SV
SERVO 12.2010 33
