Author: Red Scholefield
Edition: Model Aviation - 2013/02
Page Numbers: 101,102,103
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For the serious electric flier: setting up your battery test facility

Red Scholefield [email protected]

You have finally taken the leap. You sold all of your glow/gas motors and support equipment and converted what glow/gas–powered models you have to electric. It is time to get serious about supporting your electric-powered models and spend some of the savings you are getting on fuel and paper towels.

Attempt to establish a separate area in your shop for your battery equipment. Chargers, battery packs, and associated equipment don't mix well with balsa chips, dust, tools, metal debris, glue, solvents, etc. Maybe mine is overkill, but this will give you an idea of what I am writing about.

Chargers

There are plenty of choices. Most manufacturers have apparently settled on the four-button configuration. One thing that can be said is that balancing capability is a must to ensure maximum life from your LiPos.

Multi-chemistry chargers are a good idea if you are still using Ni-Cds or NiMHs. I find multi-chemistry chargers useful when charging my cordless tools, some of which were converted to charge LiPos because the original packs bit the dust.

Are multi-port chargers a better choice than single-output chargers? Although I have some multi-port chargers, I favor using several single-output units because a single failure won't put me out of business. It is a shame that the Cellpro 4S is no longer in production because three or four of them cost less than most multi-port units. The Cellpro Multi-4, although more complex, is an option.

Wattmeter

Second only to chargers, a wattmeter is a must for any electric flier to determine the amount of power his or her setup is drawing. There are a number of them available that all essentially do the same thing—giving you voltage, current, watts, and amp-hour readouts. Be on the lookout for the discontinued Medusa Pro that allowed you to plot the readings on your computer.

Computer

Although it might be considered a luxury, there are a number of charger systems that connect to your computer for establishing charge regimes or to record what is happening during charge/discharge of your battery. A laptop offers more flexibility, but nearly any computer will work.

A computer is mandatory if you want to use some discharge devices such as the CBA Battery Analyzer. A computer also allows you to take advantage of the capabilities of some of the more advanced chargers such as the Cellpro PowerLab 6 or PowerLab 8.

Discharge Capability

Some chargers have discharge capability, but rarely in the range that your batteries actually reach in real use. Although I have found that the CBA Analyzer is a great unit, it is somewhat limited in the amount of load it can simulate.

It's useful in establishing a baseline performance for packs because you can lay one discharge over another to visually track performance deterioration over time. It also requires a computer.

Test Stand

It is important to be able to test your batteries, especially in an environment as close to the one that you will see in your application. This is easy to achieve. A simple motor test stand created from a piece of pine to hold the motor and ESC will work. It can be made to accept your motor-mounting method and then clamped in a vice or to the end of your workbench for testing.

You should have a wattmeter and a servo tester to complete the setup. It is possible to use your receiver if you don't have a servo tester, but the setup gets more involved. Servo testers are fairly inexpensive—anywhere from $5 to $50; however, you can make your own. This is a good way to test various propeller loads. Remember that a spinning propeller can be as deadly on the bench as it can be on your model. It is a good idea to set up the motor and propeller so that it doesn't blow away whatever project you may have on the bench.

Power Supply

Because many chargers operate from only a 12-volt source, a good power supply wired to multiple banana jack outputs adds a lot to your capability. I have found that the Pyramid line of power supplies works nicely. Something in the 25- to 40-amp range can handle multiple chargers. You don't need one with meters, but I like to see what they are doing.

Instrumentation

Instrumentation is mandatory in anyone's shop. Digital multimeters are available from Harbor Freight for less than $5. More complex units featuring computer interfaces for recording readings are also available from electronics shops such as Radio Shack.

Correction

In my November 2012 column, I made an error in stating that the storage voltage for LiPos was 3.6 volts per cell. It should have read 3.8 to 3.9 volts per cell.

Although the "Battery Clinic" column is published quarterly, there is no reason to keep your battery problems and ideas to yourself. Please share them.

Don't have an email connection? Then drop me a note at the address listed in "Sources." Include a self-addressed stamped envelope if you want a personal answer.

SOURCES

Transcribed from original scans by AI. Minor OCR errors may remain.