This is how we made the battery packs for Alabama Slammer. This procedure can be done by one person but we found that a third hand and a second mind is helpful at times. All the parts and tools are readily available at local electronics shops, R/C shops and hardware stores. Good luck and feel free to email us if you have any problems building your battery pack.
Sub-C R/C matched racing batteries - Pro-Match
Shrink tubing for cells (supplied with the batteries)
Shrink tubing for Packs (available at local R/C shops)
Sandpaper, 600 Grit
Solder, standard electronic 60/40 rosin core
Electronics grounding braid, 1/4 inch wide
High strand car audio wire, 10-12 gauge
R/C low resistance high amp connectors
Large soldering iron (100 watts or higher)
Industrial heat gun or high power hair dryer to shrink heat shrink tubing
Needle nose pliers for holding items while soldering
Cheap flat blade screwdriver for holding down braid while soldering
Tin snips for cutting wire and braid
Sharp knife for cutting wire insulation
Home built battery fixture or a professional jig
Gloves to keep your hands cool while soldering
Digital multi-meter (a cheap one is fine)
Start by putting shrink tubing on each cell. The tubing provides additional protection to the cell from abrasion and cuts. If you are concerned about dissipating heat you may decide to leave it off.
The matched cells that we bought from Pro-Match came with the shrink tubing for the cells.
|We then used a heat gun to shrink each end, then the middle of each cell.|
|It is important to clean the ends of the
batteries so solder will make a good connection as quickly as possible.
We used ultra fine 600 grit sandpaper that was torn into strips. One strip was used for 10 cells and then discarded.
|Make sure that the soldering iron has a
small blob of solder on it so that there will be good heat
transfer. Touch the soldering iron to the end of the battery and feed
solder to the junction between the soldering iron and the battery. The
pool of solder should be just enough to cover the positive end of the
cell (about 1/4 inch). The pool of solder should be about the same size
on the negative end.
This step should be done in several seconds so you do not overheat the battery. If it is taking too long, set the battery aside and let it cool before trying again.
|The braid is cut to size with tin snips. The
length depends on the size of the cells and their intended
One quarter inch of the flat braid is tinned on each end.. It does not hurt to let it cool and add additional solder. How much solder to put on the braid will depend on how much solder you put on the batteries when you tinned them.
|We built a fixture that would clamp the
batteries in a straight line. Here we used a piece of wood and clamped
the batteries with a piece of steel on top of a piece of foam.
Note that a flat blade screwdriver is used to hold down the braid while it is being soldered. Make sure that you do not put a strap across the batteries in a way that would short two cells out ( I never did that - I swear!).
The same precautions apply as before, if you do not have a successful joint in several seconds, let the cell cool off before trying again.
|Here is a closer view of what the soldered
cells look like. Remember that the cells that do not have a piece of
braid soldered across the top have a piece soldered on the bottom. That
way the plus side of one is soldered to the minus side of the next.
Make sure that the cells alternate - plus side up, minus side up, plus side up, minus side up.....
|When you are through, the cells will be able
to be pulled into a string as in the picture shown. Give it a good tug
to make sure that the solder made good contact.
This is a good time to measure the string of cells to make sure that no batteries are in backwards or that there are no bad cells. Measure from one end to the other with the DC volts setting on a multi-meter. You should read about 1.3 volts multiplied by the number of cells. We had 10 cells per string so the reading was about 13 VDC.
We used 10 gauge high-strand wire for my connections. 12 gauge wire is
satisfactory and is recommend if you are inexperienced with soldering.
One end of the red and black wires were tinned in the same way that we tinned the braid. Let each wire cool and apply additional solder on the
wires to assure adequate solder for a good connection.
We then soldered the Red wire to the positive side and the black wire to the negative side of each string of cells. Expect your fingers to get hot while you are holding the wire while the solder cools. You many want to wear a glove for this step. If the wire moves before the solder hardens, you will have an unreliable connection.
I did not use a flat blade screwdriver to hold down the wire because it was stiff enough to apply pressure on the top of the cell. Another reason was that I do not have three hands.
After pulling on the wire connections to make sure that they would not
easily break off, the string was stuffed into heat shrink tubing.
It took a few tries to find the easiest way to stuff the cells. Pushing the wire through was difficult because the soft insulation wanted to stick to the walls of the shrink tubing. A piece of coat hanger with a hook on one end helped us pull it through.
|The pack is flattened by hand to insure the the final product is straight.|
The pack was heat shrunk on the ends first to tighten up the pack. Then the middle was shrunk down.
If you use too much heat the shrink wrap will get holes in it.
|This is what the final product should look like. Note that the pack on the left was done without a fixture. The one on the right was done with the alignment fixture.|
This is a picture of the assembled cells, it took about a week and all of
our spare time to get to this point.
We bought some low resistance high current R/C battery connectors, tinned them and soldered tinned wires to the connectors. Don't forget to put the heat shrink tubing on the wire before you solder them. All exposed electrical connections should be covered with heat shrink tubing or electrical tape at this point.
Photo coming soon
|Here is a picture of a pack with the connector attached. We used Deans plugs. There are many quality connectors to choose from in R/C shops.|
This is a picture of 8, ten-cell packs mounted in Alabama Slammer.
That amounts to 80 cells capable of supplying 140 amps at 26 volts DC for 5 minutes.
|Here is photo of how the batteries look in the overall layout in Alabama Slammer.|
This is a picture of what your living room could look like while working
on the electronics portion of a combat robot.
It is a mess, but hey! it was fun.
E-mail Redneck Robots
©2001 Redneck Robots. All rights reserved.