This battery works with AltusMetrum and Featherweight GPS tracker and Blue Raven

This is a small and lightweight battery based on advanced Polymer Lithium Ion (LiPo) chemistry, which offers the highest energy density currently in production. Each cell provides a nominal output of 3.7V at 900mAh capacity, making it a reliable and efficient power source. The battery comes terminated with a JST PH 2.0 connector; however, it is important to note that the wiring to the JST connector is reversed compared to most similar batteries on the market. This means the positions of the positive and negative leads on the connector are swapped. This configuration is designed specifically for compatibility with Featherweight and Altus Metrum Electronics.

Battery does not include built-in protection against overcurrent. Unlike typical LiPo batteries designed for general use, this battery is intentionally manufactured without a built-in overcurrent protection circuit. This design choice addresses a specific need in applications like rocketry, where the use of pyrotechnics, such as e-matches, demands uninterrupted current flow to fire charges reliably.

Here’s why this matters: Overcurrent protection circuits in LiPo batteries are designed to react to sudden, excessive current draw to prevent dangerous outcomes, such as a chemical fire. In certain scenarios, such as if an e-match draws too much current—potentially due to a short circuit caused after ignition—the protection circuit might shut off current flow. While this is a safety mechanism for general electronics, it can cause critical failures in rocketry. For example, during a rocket’s apogee event (when the drogue or main parachute charge is ignited), if the battery’s protection circuit activates, it could cut power to the flight computer or altimeter. This failure would prevent the main parachute from deploying, leading to a dangerous, uncontrolled descent. Such an event could damage the rocket itself or, worse, pose a serious risk to people or property below.

To mitigate this risk, the rocketry community often uses small-capacity LiPo batteries, like this one, without built-in protection circuitry. These batteries provide uninterrupted power even during the high-current demands of pyrotechnic events. Additionally, the brief nature of the firing circuit closure (typically less than one second in dual-deployment altimeters) ensures that the battery remains functional and unlikely to sustain significant damage. However, it is important to handle such batteries responsibly, as the lack of overcurrent protection does carry its own inherent risks.

By omitting the protection circuit, this battery is specifically tailored for high-demand, time-critical applications like rocketry, where reliability in critical moments outweighs the added safety offered by a typical protection circuit. Users must take care to ensure proper handling and use this battery only in devices designed to accommodate unprotected batteries.

Note: Be careful with the JST connectors. They can stick in pretty good and tugging on them can damage the connector.

Dimensions: 48 x 29 x 5 mm (±1 mm)
Weight: 18g

Features:

• Excellent long-term self-discharge rates (<8% per month)
• Robust power source under extreme conditions (-25 to 60C)