Build an FTC Battery Load Tester

Load Tester Circuit Diagram

• Batteries used in our robots can always be recharged, but over time, some batteries lose their ability to hold that charge.

• A voltmeter only shows the current voltage, not capacity.

• Bad batteries can have a good voltage after charging, but have very limited capacity.

• Load testing quickly indicates whether a battery has lost its capacity to hold a charge.

We have developed a safe, low-cost method of testing the 12 Volt Tetrix batteries used in FTC competitions. And our load tester found a bad battery that could not have otherwise been detected!

Commercial load-testers for 12 Volt batteries are designed for measuring car batteries, typically applying a 50 amp load or more. To apply an appropriate load for Tetrix batteries, we used two 50 Watt fog lamps from an auto-parts store.

Building directions are available in two downloadable formats below: PowerPoint or PDF. Same content. There is also a file link for the Excel test data and performance graph.

We welcome your feedback and improvement suggestions! Use the Contact link to drop us a line!

Photos and diagrams here are clickable for larger versions.

Voltage vs Time, Tetrix battery under 100 Watt load