Sealed Lead Acid (SLA) Battery Safety

Know your battery

The standard FRC robot battery is a 12V, ~18Ah sealed lead acid (SLA) non-spillable battery (common examples include the MK Battery ES17-12 and EnerSys/Genesis NP18-12 class). WPILib's Robot Battery Basics states it can briefly supply over 180A and arc over 500A when fully charged — enough energy to weld a dropped wrench to the terminals. Treat every battery as live and dangerous.

The acid hazard

The manual carries a CAUTION: FRC batteries contain sulfuric acid (H₂SO₄), a corrosive liquid that burns eyes, skin, and clothing. A battery that is visibly damaged in any way is dangerous and unusable — do not take a chance. A dropped battery may be cracked even if the crack is not visible and may leak later, so periodically inspect for damage or leaking electrolyte. If acid contacts skin, flush immediately with a large quantity of water and seek medical treatment. Treat damaged batteries as hazardous material per their SDS.

Keep these safety materials on hand

FIRST recommends teams always have available:

• A box of sodium bicarbonate (baking soda) to neutralize spilled electrolyte (baking soda is harmless and reacts with the acid).
• A pair of acid-resistant rubber or plastic leak-proof gloves.
• A non-metallic leak-proof container to hold a defective battery.

If a battery leaks

Neutralize the spill with baking soda on all wet surfaces, follow the SDS emergency instructions and notify a mentor, put on safety glasses and gloves, place the battery in the leak-proof container, neutralize acid on the gloves before removing them, and dispose of the battery as hazardous material. At an event, immediately send anyone who contacted acid to the First Aid Station / EMTs, report it to the Pit Administration Supervisor (provide your team number) so they can file a Medical Incident report, and Pit Administration will contact Event Management.

Charging and handling

• Never carry or transport a battery by its power leads — pulling on the cables damages the lugs, tabs, and internal connections, raising internal resistance over time. Carry it by the body.
• Do not short the terminals. If metal tools or parts bridge the terminals you create a direct short with intense heat and possible explosion, so you must cover all exposed battery terminals and connections with insulating material such as electrical tape or tubing.
• Keep the charging area clean and orderly, and place chargers where air circulates freely — chargers can fail without ventilation.
• Do not charge above the manufacturer's maximum recommended rate. Use a smart charger rated 6A or less per battery with a maintenance/float mode; chargers over 6A are prohibited in FRC pits. Let batteries cool (about 15 minutes) after a match before recharging.
• Never disassemble a battery or pry out a stuck battery with tools — you may puncture it.

Inspection and disposal

Inspect each battery before and after every round of competition for a cracked case, bent terminals, or leaking electrolyte. Many teams use a load tester (the CTR Electronics Battery Beak, am-0995) to check state of charge and internal resistance under load — roughly under 0.015 Ω is good, and a battery above about 0.020 Ω should be retired from competition. Dispose of batteries properly: most automotive-battery retailers accept and recycle SLA batteries at no cost.