Finding better batteries

Our battery search takes us far and wide. There are a number of interesting possibilities, all of which must be investigated. The Internet again proves it's value as a research tool.

We hear rumors that radio control electric planes were doing amazing things with batteries. Light batteries giving high amps for long runs. Since R/C planes are small, their batteries are relatively inexpensive. A number of hobbyist are experimenting with lithium polymer batteries. Some battery suppliers are taking their feedback and trying to give them batteries that meet their needs. Much of this back and forth takes place online. http://www.rcgroups.com/forums/index.php is an active place.

One of the most active and responsive lithium polymer battery companies is Kokam Engineering. The company president, JJ Hong, is an active participant at the forum, answering questions and supporting testing. Kokam batteries are the RC plane market leader.

Speaking directly with JJ, we learn that Kokam has EV size batteries and would be interested in seeing them raced. The specs are impressive. The cells are rated at the 1 C rate. The 70 amp-hr 3.7 volt nominal cell weighs only 4.3 lbs and can deliver 350 amps continuously and 700 amps peak. The 40 amp-hr cell weighs 1.76 lbs. It is rated at 200 amp continuous and 400 amps peak.

We request a 40 amp-hr and 70 amp-hr sample cell.

The next step is to evaluate the batteries. To do this, we construct a computer controlled battery charger/discharger - The Battery Evaluator. With the Battery Evaluator, we can specify a charge algorithm and the discharge amp rate while recording amps and volts and battery temperature every 0.1 of a second.

The full power tests results are impressive.

We meet with Kokam President JJ Hong and Vice president Dr. Joon Kim. They were excited about the possibilities of racing their batteries and what we could all learn from the exercise. We agreed to proceed.

 

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High Amp battery tests

 


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