Building an RC Battery Pack - A Basic How-To
If you love RC, you know the importance of a battery pack. The type of batteries you choose, how well your pack is assembled and how efficiently you charge them are all important aspects to powering your RC vehicle. Sure, you can buy a battery pack pre-assembled, but you can also build your own and get the satisfaction of designing and powering your own vehicle.
The first thing you need to do is when you decide to put together a battery pack is what you are powering and how much juice you need. You also need to think about the following:
1. Look at the chassis of your vehicle. The kind of vehicle doesn't matter as much as the amount of space in which you have to maneuver. The batteries may need to be oriented in a flat pack, a clustered pack or as both. You should also think about the distribution of weight in your vehicle - whether the battery weight is going to be distributed in a side to side or back to front manner. In some cases your chassis space for a battery pack is not adaptable, so be aware of those constraints before you start.
2. Look at the motor powering your RC vehicle. Depending on the power requirements, you'll be able to determine how many batteries or cells you need. This is also when you can decide the type of batteries you'll use - if you want to keep your NiMH batteries or upgrade to LiPo.
3. Determining your voltage is really a simple matter of addition. A standard cell voltage is 1.2v, so wired in a series - 12 batteries will add up to 14.4v - which would power an 14.4 volt RC electric motor.
Next, you'll need to gather your battery pack supplies - so here's a sample shopping list. Remember, we're assuming we're creating a battery pack with 14.4v, as in the example above:
o 12 Batteries or Battery Cells
o 12 Battery Bars (you can order battery bars in bulk if you plan to build more than one pack and save $)
o Wire: You'll want a higher quality 12 gage with a high strand count. This type of wire, with these characteristics will be more flexible which is ideal as well as being more efficient for power transmission.
o 80-100 Watt Soldering Gun. You'll want a gun because you can be more exact and quicker - this is necessary because of the heat sensitivity of batteries. The faster and more specific you can be, the less likely you'll be to damage the battery.
o 60/40 Solder. This is higher quality - also important for quick and accurate work and avoiding battery damage.
o Flux. This is a chemical cleaning agent that removes oxidation from metal to facilitate soldering. You can use liquid or paste flux when assembling a battery pack.
o Shoo Goo or Goop. This fast drying adhesive will be used to bundle the batteries together.
o Battery Pack Assembly Jig - optional. These assembly devices align the batteries properly and facilitate a tidy battery pack. The batteries end up basically looking like cord wood - tidily bundled.
o Soldering "Helping Hands" - optional. These devices allow you to hold things in place while you solder.
o Another optional timesaver is to get a "Helping Hands" accessory for your soldering station.
o Multi Meter. You need a good multimeter to test voltage and polarity.
o Wire strippers and Wire Cutters. These tools will help you handle, strip and properly cut your 12 gage wire.
o The final component is the shrink wrap which will go around the entire assembly and keep it tidy. You'll also need a heat gun to heat and shrink the wrap.
So, you've identified how to orient your batteries and how many you need - now you get to work on assembly. For this example, we're assembling 12 battery cells - 6 down one side and 6 down the other.
Once you identify where the batteries are going in relation to your chassis and how they are going to be laid out, you can begin. For this example, let's say we're doing 6 down one side and 6 down the other side.
Just to make sure we're on the same page, the ultimate goal here is to be running wire from the positive terminal of your first battery to the positive terminal on the electric RC motor and then running a wire from the negative terminal on the last battery in your pack to the positive terminal of your other battery pack, thereby creating a completed circuit.
This mean you need to have sufficient wire to reach from the positive terminal of your first battery to that terminal and likewise from the negative to complete the circuit with your other battery pack so bear that in mind.
Orientation. Align your first cell so that positive is pointing "upwards" and negative is pointing "downwards" and then reverse the next battery so it's opposite on down the line. If you purchased the battery assembly jig, this is when you'd use it to align your cells and hold them in place.
Adhere. Stick all the batteries together with your fast drying adhesive to they are in order and aligned properly.
Flux. Use your flux now on the connection points.
Connection - Use your battery bars to connect your cells. You'll need to heat up your soldering gun and heat up the battery bar. Using the bar protects the battery and when the flux starts to bubble, you employ your use of solder. The goal is to NOT heat the battery itself. Heating the battery is not only counterproductive, since if you damage the battery it won't work, but also dangerous because the cell might explode if overheated.
You'll want to complete the same steps for the remaining battery connections. You are connecting the negative to the positive over and over again. You'll then be ready to connect wiring to your battery pack.
The wires need to be pre-tinned which mean you need to strip off a quarter inch of the protective plastic wiring sheath, use the flux to clean them - apply the flux liberally - heat your solder gun and then heat the wire and flow the solder into the wire until thoroughly saturated. You'll also want solder on the batteries so the solder will act as the connector with the battery.
Once the two, six cell battery packs are complete, you'll want to employ the shrink wrap to secure them - and you'll have your complete battery pack! Now you'll be able to power and fly your RC helicopter, plane, boat, car or truck with no problems!
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