have a charger capable of charging
both (Multiplex LN-5014).
Is the Li-Ion system more robust?
Does it require balancing or other
detailed maintenance? Besides
temperatures and fire risk, what
concerns should I have in combat?"
Wisdom of the Forums
a Li-Poly can.
While these A123s
are amazing, a little
research shows they are —
like all optimum solutions
— on the pricey side.
Buyers are looking at $8
to $14 per cell, so that's
$100++ for a 12 volt
The A123 Li-Ion cells are
certainly a good choice, but they
have their own care needs just like
any other technology. Li-Poly is also a
good choice, and again has its own
set of needs. Some of it just depends
on what you are building.
Always balance lithium-based
cells if you can, no matter which
exact chemistry. Even if the
manufacturer tells you it doesn't
need balancing, your cells will be
happier if you do.
Some points to consider for
it is impossible."
1) They are easily physically
damaged. They are very light, so the
metal casing is pretty thin, and they
dent and bend more easily than
other chemistries. Shock pad
2) They will get out of balance.
Not all cells are the same, and newer
cells are much better than old. Try to
balance-charge at events if you have
time, but if you have to just bulk-charge, hope they stay close enough
to not damage any of them.
Understand you're taking the risk of
destroying them if you do this.
3) Specs on some say 70A
continuous and 120A peak. They will
do over 200A on a dead short.
4) Do NOT trickle charge to
balance like you would with NiMH or
NiCD. The cells will just continue to
climb in voltage and you will kill
Lots of layouts are done on
graph paper. Of course, it's much
easier to revise on the computer.
A good, free, easy 2D CAD
program is called eMachineShop
Another popular answer is
Google Sketchup. It's free and
intuitive, and the documentation is
really good. The only downside is
that it is hard to import and export
other CAD formats. If you are a
student, you can also get Autodesk
Inventor for free sometimes. With
small robots, CAD software is nice
because you can print out cutting
"I'm unfamiliar with that Robot
Marketplace product, but I'd
*assume* that the matrix in the
composite is an epoxy. You want
your adhesive to be as chemically
similar to your composite matrix as
possible. Before bonding, you want
to clean both surfaces thoroughly
with a solvent, abrade both surfaces
with *clean* sandpaper, remove all
debris with a clean dry cloth (don't
use a solvent again or you'll dissolve
impurities and release agents right
back into the surface!), let it dry
thoroughly in a clean environment,
"Does anyone have an opinion as
to the best adhesive for carbon fiber
like the kind Robot Marketplace sells?
In addition to gluing the two rough
sides together, I'm also looking for
advice for gluing the rough side to
the smooth shiny side of Texalium.
Then, there's UHMW. Are there
any adhesives that work well with
this stuff? I plan on using screws but
I figure it doesn't hurt
and it helps get the
holes lined up.
One responder noted: "The
Velcro tape and double-sided
mounting tape I've used stuck very
well to UHMW. So, there are some
adhesives that will stick well to
And another: "I used shoe goo to
stick it to aluminum without failure. I
wire brush/roughed up and cleaned
both surfaces. On an ant — when I
was looking for strength — I used to
use a Devcon plastic welder and had
The iMAX B8 charger came
recommended as part of this string,
to use in balancing Li-Ion cells.
Apparently, the other advantage
of A123 is they don't do the "swell
up and burn like crazy" thing like
"Shoe goo" or
'goop' — same thing —
for the carbon fiber.
And forget gluing
anything to UHMW.
I am pretty sure
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