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RC Battery Pack Building and Re-Building
One of the major problems with
most battery packs, no matter how good the battery cells are, the connections
between the cells and from the pack itself usually suck big time. These
crappy connections are typically little tin foil accordions paired with small gauge
power wires, and stock Tamiya connectors which simply do not allow free flowing
current between the cells and to your RC.
I have some decent packs, GP3300s,
PowerMax Pros, Trinity, etc.., the power wires were thin and were initially replaced with Deans Wet
Noodle 12 gauge wires and connections to the ESC were upgraded to Deans
which was a huge improvement. These slightly upgraded packs were great for
the lower current requirements
of the brushed motors I had been running. Deans and high current wires are a typical upgrade for almost any pack.
I moved to a brushless motor system however, all my packs seemed to really heat up
and performance lacked in a very obvious way. Although better than most, the PowerMaxs and even the Radio Shack GP3300s use a thicker foil
accordion connections between the cells, they are still way too
thin for the current hogging requirements of something like the Novak 4.5R brushless
The between cell connections
simply could not allow enough current flow between the cells. This
issue is typically displayed in the form of a hot battery pack. Another
indication was the fact that the ESC was pulling so much current that it
would actually brown out the receiver (yeah a lot of current). This
issues was resolved with the addition of a simple 4700mF capacitor wired
into the ESC's external battery pack slot (kind of a battery back up for
the receiver). Even with the fix, the system still lacked the power
I knew it had. The problem was I either needed better higher quality
battery packs or needed to rebuild the packs with better between cell
connections (battery bars) so all that lovely current could flow when it was needed and
not get bottlenecked at the connection points between the cells.
Instead of going out and buying new packs I decided to rebuild my old ones
first and it worked beautifully.
What are better connections
(i.e. battery bars) going to do for me? Basically the current will flow more easily from
each cell to the next with the least amount of resistance.
Resistance causes the cells to overwork themselves and heat up, heat is
bad for a battery. The hotter the pack is, the less runtime, current, and
life it will give and have, and the hotter the cells get the more
resistance. The cycle starts over with more heat and more resistance. You should see a pretty noticeable difference
in peak power, overall runtime, all with much cooler running batteries
once the battery pack is rebuilt with good quality battery bars such as
Deans Probar 3s.
Battery Pack Styles - There basically two types of
battery packs, shotgun or stick packs which stack the batteries positive
to negative like batteries in a flashlight or brick or side-by-side style
packs which are just as they sound more on these styles in the articles
Buying new cells
or rebuilding an existing pack and making a new
pack? No problem, follow, the same process as described in the articles
below. I would go ahead and buy matched cells if possible. Matched
cell packs are built with
cells that discharge from a time and voltage perspective almost
They typically will run longer with overall higher voltage than unmatched
cells. Over many uses matched cell will
eventually become unmatched cells but will still perform better in the
long run for you than un-matched cells. If you are
simply a basher (non-pro), I would recommend going with a high Mh cell like the Radio Shack
GP330 or other quality 3300mh to
4200mh cells for longer runtime.
RC Battery Pack Building and
Rebuilding Important Notes & Tips:
Before you start tearing open
packs there are some things you should know and may need to buy.
What type of configuration are
your going to use, a standard stick pack or a side by side or some
custom configuration of more than 6 cells? Keep in mind that
occasionally side-by-side packs are wider than stick packs. A side
by side pack will fit tightly in the Rustler and Stampede without
problem, however I would recommend attaching the positive and negative
leads to extra Deans Probars and bend them over the pack. This will give
the battery an extra 1/8" to fit into the battery holder better.
Are you pretty good at
soldering, soldering battery packs is a little tougher than soldering
small gauge wires especially with an underpowered soldering iron.
Do you have at least a 75W
soldering iron or more would be preferred with at least a 1/4" chisel
tip? A 30W hobby soldering iron is not gong to cut it. I use a $30 stick style 80W Weller soldering iron with a huge
1/2" tip for battery building
that tops out at 900 degrees. This big iron is more for production
work and I would really suggest nothing less to keep you from going
insane. The big thing here is the mass and
heat of the chisel tip which allows a solder joint to happens almost
instantly versus say a 50W soldering iron which may take 10-15 seconds
or longer to solder the same joint. More time means more heat stress on
the cell itself. That huge 80W Weller makes battery building a
breeze and leads to much more professional results.
Standard electrical grade 60/40 solder is recommended however a good quality silver
solder will be harder to solder but will improve pack performance
You will need 5-7 battery bars
per 6 cell battery pack (7 battery bars are needed if you do not want
the power leads to attach directly to the batteries - sometimes
clearance dictates the extra bars).
Remember this is the critical connection between your cells, so buy at
least Deans ProBar 3 battery bars. I have seen some out there
thicker and wider, but I will let you be the judge as to whether these
are overkill versus an upgrade.
Do you have spare large gauge
power wire for the rebuild (sometimes you find that your recycled power
lead wires are too short).
You will need Deans or other
low resistance power connectors if you don't already have them for both
the male ESC and female Battery connections.
1/2" battery pack shrink wrap - depending on your application.
IMPORTANT At least 2 cell shrink wraps for
each naked un-shrink wrapped cell such as the ones in my PowerMax Pro
stick packs. DO NOT ATTEMPT TO BUILD A PACK WITH NAKED CELLS YOU WILL
BLOW ALL OF THEM - TWO LAYERs OF SHRINK WRAP MINIMUM. So in my case I needed 12 cell shrink wraps for one 6 cell
pack of naked cells. Naked cells will not have any plastic
coating and look silver, if in doubt, add a layer of cell shrink wrap. Also a
really great idea in the RC Car action article on having an extra layer
on each cell in regard to gluing cells together.
Heat shrink should be done with a heat gun
or hair dryer and not a torch as I found out. It will simply melt
apart with a torch.
Custom Logo'ed pack as
show above, just glue a 1 5/8" wide logo of your choice onto each
cell with simple craft glue before shrink wrapping each cell.
Some power lead sized shrink
wrap tubing for the connection ends.
A Dean's speed jig for battery
building is helpful, however an improvised cell vise using a ruler and
some masking tape will also work
well. I used a strip of masking tape on both sides of the cells
taped to a ruler to
hold the cells together and straight while I was soldering the cells.
A battery jig is very helpful as an extra hand and worth the $10-$15.
Always start by rebuilding your most crappy
performing pack first. It will take you at least 2-3 packs to
figure things out and get a professional looking pack.
Want out? You starting to think
"Dude this is just too much work?" Well it's actually pretty easy
and simple which probably takes far longer to explain than actually
building a pack, however there is a process to follow and about $7-$10
worth of materials to get your battery pack back in shape.
I have heard build good packs and may be an option if you either don't have
the soldering skills yet or just at the point where it would be worth the
money for someone else to do it.
There are the articles I would HIGHLY recommend you read them all before proceeding with tearing
apart your battery packs.