Build A Receiver Pack

Your receiver battery is the heart of your radio-controlled helicopter. If that battery fails, a crash is virtually inevitable. There are good receiver batteries on the market, but learning how to build one will give you extra confidence that your battery is up to the task.

Picking the right cells
Selecting the right batteries is first. You want to pick a high-quality cell that has enough capacity and can be built in a configuration that will fit your model. The 1100-2500 mAh AA packs will work okay for 30- or 50-sized helis. I prefer to go with sub C cells for 50- to 90-sized models, although people are often successful with A-sized batteries for the larger models. Whatever cells you decide to go with, make sure they are from a reliable source and have adequate capacity. Smaller cells tend to have higher internal resistance and less capacity, as well as less ability to deliver current.


Building your pack is as easy as following these step-by-step instructions:
1. Rough up the surface of the cells on the ends to help the solder stick.
2. Pre-tin the ends of the cells.
3. Arrange the cells in the layout you want so that you can solder the cells together in a series configuration. (diagram of a simple series circuit)




4. Glue the cells together with Goop.
5. Begin at the positive terminal at the end and solder the red servo lead to it.
6. Begin with the first cell to the second with a battery tab or solder braid.
7. Continue connecting the cells in the pack one at a time.
8. Solder the black wire of the servo lead to the negative terminal at the end of the pack.
9. Measure the voltage of the pack to make sure you are getting your expected voltage.
10. If the pack is providing adequate voltage, proceed to shrink-wrap the pack.
11. Cycle the battery several times before use to make sure it is working properly.







Things to Watch For
Make sure your new battery is working properly before committing a model to flight with it. Use a charger that can display how many mAh the battery actually took, and cycle the battery several times to confirm that it's working. To cycle the battery, simply charge and discharge it several times to get an accurate idea of its useful capacity. When you solder the cells, use a high-quality iron and avoid getting the cells too hot. Your iron should be hot enough so that you can just touch it to the cell and almost immediately start melting solder onto the surface. If you have to hold the iron on the cell to get the surface hot enough to accept the solder, the whole cell may heat up and cause damage.
(closing picture)

Conclusion
Sometimes you just can't find the right pack to fit your needs. After a crash that's caused by a suspicious failure, a little peace of mind goes a long way. Making your own battery gives you some quality control over your model's power supply. If you want to get really precise, you can even charge and discharge the cells before construction. This will ensure that they're delivering similar capacity and are at the same voltage, which means they'll be balanced when you assemble the pack.