Battery Management

Why batteries matter so much

A weak or sagging battery causes the most maddening failures in FRC: the robot browns out mid-match, motors cut, and the roboRIO may even reboot. When battery voltage sags too low the roboRIO enters brownout protection to keep itself alive — on the original roboRIO this happens around 6.3V , and on the roboRIO 2.0 the default is 6.75V (software-adjustable). Many “the robot died on the field” mysteries are really just a tired battery. Disciplined battery management is one of the highest-return habits a pit crew can build, and it’s cheap insurance for every match.

Know your battery

The standard FRC robot battery is a 12V sealed lead-acid (SLA) battery rated about 18Ah (the classic example is the MK ES17-12 , sold by AndyMark, REV, and others; it weighs roughly 13 lb). Per Game Manual rule R601 the robot must use 1 and only 1 non-spillable SLA battery (12V nominal, 17–18.2Ah) — lithium and other chemistries are not legal, so always confirm what the current Game Manual allows before using any battery, because battery rules are inspected and enforced. Whatever you run:

• Use the correct connector (typically an Anderson SB-50 connector) and the required inlinemain breaker (a 120A self-resetting breaker) per the rules.
• Keep terminals and leads secure and undamaged — a cracked lead or loose lug is a brownout waiting to happen.

Charge and rotate

A reliable rotation looks like:

1. Multiple batteries in the fleet so you always have a charged one ready (competitive teams often carry several).
2. A dedicated charger (or several) running in the pit; many teams use smart chargers that won’t overcharge.
3. Label and number each battery and track which is fresh, charging, or resting.
4. Let a battery rest briefly after charging before a match for the most accurate state, and never put a just-discharged battery straight back into the robot.

Test before you trust

Don’t guess — measure. A common tool is a battery beak / battery analyzer (e.g., the AndyMark Battery Beak), which reports voltage and internal resistance. Rising internal resistance is the tell that a battery is wearing out even if its voltage looks fine. Retire batteries that test poorly; a battery isn’t worth losing a playoff match.

Handle safely

These are heavy, high-current batteries — treat them with respect:

• Never short the terminals ; a dropped wrench across the leads can weld and burn.
• Don’t drop or crush them; SLA cases can crack and leak acid.
• Secure the battery in the robot so it can’t shift in a collision (robot inspection checks this).
• Dispose of dead batteries properly through recycling, not the trash.

The match-day habit

The simple rule that prevents most failures: every match gets a fresh, tested battery. It goes in during the turnaround as part of the checklist, the spent one goes straight onto the charger with its number logged, and the cycle repeats all day. Boring, repeatable battery discipline is invisible when it works and catastrophic when it doesn’t.

Key takeaways

• Weak batteries cause brownouts (roboRIO ~6.3V, roboRIO 2.0 default 6.75V) and mid-match failures; battery discipline is high-return.
• The traditional battery is a 12V ~18Ah SLA (e.g., MK ES17-12); confirm current Game Manual rules before using anything else.
• Use an Anderson SB-50 connector and the required 120A main breaker; keep multiple numbered batteries on rotation with chargers.
• Test with a battery analyzer (internal resistance, not just voltage), retire weak ones, and put a fresh tested battery in every match.

This lesson was adapted from learnfrc.com.