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We figured if we wrote that title
block in a bunch of languages, you might get the idea that this
next bit of information is just too important to miss. Lithium-polymer batteries can be
very dangerous if not treated and cared for properly. We
assume no liability or responsibility for how you choose to use
them. Please follow all manufacturer's recommendations
exactly as they describe. There are a thousand different
ways to burn up a pack, catch your truck on fire, or otherwise
put yourself and others in danger. USE AT YOUR OWN RISK!
The real question should be, why
not??? Here's your basic rundown on lithium-polymer cells:
ADVANTAGES
- Power-to-weight ratio is
insane.
- Much lighter than
standard NiCAD or NiMH cells.
- In some cases they're
nearly 1/3 the weight.
- Higher voltage from a
much smaller package.
- 7.4V for 2S packs and
11.1V from 3S packs.
- It would take over (9)
2/3 cells to get that kind of voltage.
- Higher mAh ratings
- Longer run time
- Cooler-running cells.
- Provides more constant
voltage throughout the run of the pack
- Lower internal
resistance (and we hate resistance!)
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DISADVANTAGES
- Requires extremely close
monitoring of cells during charging as well as
discharging, this includes while running them in your
truck.
- Special chargers must be
used to charge packs, which can be more expensive than
standard chargers (for the good ones anyway).
- Packs are typically more
expensive than standard packs, ranging from $29 to $99
for packs that would fit into the RC18T.
- Not every lithium pack
will fit nicely into the RC18T
- Some modifications are
required in order to fit some of the best lithium packs
available.
- Low-voltage warning or
cutoff circuitry is required to avoid over-discharging
packs.
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We've compiled a list of
lithium-polymer battery packs from various manufacturers that
will fit into the RC18T without too much modification.
Click on the chart below to enlarge it or download the .pdf.
DOWNLOAD THE .PDF
Okay, we're going whip out a
little "i, RC18T" aktion with the Three Laws
for choosing the right pack for the RC18T:
Law 1.
The pack must be rated at least 1000mAh.
Law 2. The pack must have a minimum discharge
capability of at least 10C.
Law 3. The pack must fit into the truck safely. |
These are the absolute minimum
ratings you can use. At no time should you violate any of
the Laws in order to comply with just one or two of the Laws.
Last week I found a great pack that would fit into the truck
with no mods, and weighs just over 32 grams, but it's only rated
at 850mAh with a discharge rating of 8C. Can I use this
pack? No! How about a pack that is rated for 2400mAh
with a 20C discharge but is 110mm x 45mm x 20mm? No!
It doesn't fit the truck, well not easily anyway, without
requiring half the chassis to be cut and there's no way that the
body is going to fit on there after all that.
NOTE: these Laws only apply to
280/300/370-sized motors. If you've got a bigger motor in
your truck, or a brushless motor, it's better to get the highest mAh, highest C pack you can find.
| As long
as you can safely fit the lithium-polymer batter pack
copmpletely into the truck, get the highest mAh and
highest C rating you can find. |
Why do we care so much about
physical size? Because lithium-polymer batteries are
dangerous, and if you've got half the pack exposed to the rocks,
the street, and anything else that might strike the pack while
your driving and crashing, you could easily puncture the pack
which may cause it start on fire. You need to keep the
pack protected, keep the pack safe, and the only way to do that
is keep the pack within the physical size of the chassis with
the lid on. Period.
There is only one pack that we've
found (although there could be others) that
exactly measures the same dimensions as a regular 2/3A 6-cell
pack that would fit perfectly in the RC18T and that's the
HiModel 1700mAh pack. We haven't run the pack, but it's
got some good numbers and would be your best bet if you didn't
want to modify the chassis at all. However, if you want a
little more run time, and don't mind modifying the chassis, you
may want to pick a different pack. Mainly, all of these
packs require that the tub-edge be cut down flat with the
chassis on the battery side of the truck. So how is the
pack suppose to stay in there? Keep that battery strap on
there nice and tight! Or you can figure out some sort of
strap to keep the battery in the truck. If we think of
something, we'll post it here.
Our Top Picks
Thunderpower 2100mAh - High mAh, high C rating, small,
light, 3S is only 20mm tall.
MaxAmps 2100mAh - High mAh, highest C rating,
small, heavy, 3S is 26mm tall.
HiModel 2200mAh - Highest mAh, high C rating,
small, inexpensive, 3S is 24mm tall.
Polyquest 1800mAh - Good mAh, highest C rating,
small, 3S is 21mm tall. |
More to come...
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