Here are the guidelines for usage of LiPo (and other) batteries at a Pi Wars competition. They relate to the usage, storage and charging of the batteries.
A technical inspection will be carried out on the day that will look at what batteries you are using to determine that they are safe to use.
Usage
- Always use a low battery alarm when the battery is connected to ensure that you do not over-discharge the battery.
- Do not leave your robot unattended if the battery is connected.
- Ensure you use appropriate battery connections that can handle the current draw (XT30 and XT60 connectors are a great start).
- We recommend having a fuse between the battery and the robot electronics so that, should anything short out or draw more current than anticipated, the fuse trips first.
- Any wires and electrical connections should be insulated to reduce the chance of an accidental short circuit.
Storage
- Store the batteries in a fireproof bag or a heat proof (insulated metal) box and keep them in a cool/dry place out of the way.
- Do not store LiPo/other batteries in fully sealed containers. If a battery should unfortunately start to catch fire, a sealed container would increase the risk of it turning into an explosion.
- Do not leave LiPo/other batteries unattended on tables or on the floor, especially if connected to anything.
Charging
- You must charge batteries outside at the designated charge points at the event using LiPo-specific chargers.
- Check that the charger settings match the battery that is connected. It is critical that the cell count on the charger matches the battery (don’t trust any autodetect feature!).
- We recommend that batteries are “Balance Charged” rather than just “Charged” to ensure that each cell in the battery has the same voltage. This helps stop over-charge and over-discharge issues.
- Batteries on charge should always be charged inside a fireproof LiPo charging bag.
- You must ensure that no battery is left charging unattended. Please ensure a responsible adult is monitoring the batteries on charge in case of an issue.
- Do not over-charge or over-discharge LiPo/other batteries and ensure you are not exceeding the charging rate of the specific battery. We recommend not exceeding 1C charge rate. For example, charge at 1A for a 1Ah battery, or 0.5A for a 0.5Ah battery.
Emergency procedure
If a LiPo should unfortunately get overly hot, smoke, or start to expand/puff out, disconnect the LiPo (if safe to do so) and take it (and any connected robot/electronics) outside immediately to the designated battery fire safety spot. Place the battery, and anything else connected to it, in a metal container and cover with sand. Do not inhale any of the smoke and beware that it may catch fire whilst being moved. If possible, whilst one person is moving the battery, a second person can clear the exit route to ensure that no-one else gets in the way.