Battery charging safety requirements

Only designated persons may change or charge batteries under 1917.157(a).

• Designated means the employer must identify which employees are authorized to perform battery changes or charging. Documenting who is designated and ensuring they understand safe procedures is a practical way to meet this requirement.
• Employers should ensure designated persons know the other requirements in 1917.157.

Battery charging and changing must be done only in areas that the employer has designated for that purpose, per 1917.157(b).

• Designated areas should keep charging operations separated from general work traffic and other hazards and be chosen with ventilation, ignition-source control, and spill-response in mind.
• See related ventilation and ignition-source rules in 1917.157(h) and (c).

No—smoking and other ignition sources are prohibited in battery charging areas under 1917.157(c).

• This prohibition reduces the risk of fire or explosion from gases produced during charging.
• Employers should post signs, enforce a no-smoking rule, and control hot work or open flames near charging areas.

Yes—filler caps must be in place when batteries are being moved, as required by 1917.157(d).

• Keeping filler caps in place prevents electrolyte spills and reduces the risk of exposure to corrosive acid during handling and transport.

Yes—the parking brakes must be applied before batteries are charged or changed in a vehicle, per 1917.157(e).

• This prevents vehicle movement during the charging or changing operation and reduces the risk of injury and equipment damage.

When connecting a jumper battery to a vehicle battery, the ground lead must be connected to ground away from the vehicle's battery and the vehicle's ignition, lights and accessories must be turned off before making connections, as required by 1917.157(f).

• Connect positive-to-positive first, negative-to-ground away from the battery (to reduce the chance of sparks near hydrogen off-gassing), and only then complete the circuit.
• Turn off ignition and accessories to avoid electrical surges and reduce fire risk.

Batteries must be free of corrosion buildup and cap vent holes shall be open under 1917.157(g).

• Remove corrosion buildup safely (use appropriate PPE and cleaning methods) so terminals make good electrical contact and vents are not blocked.
• Open vent holes allow gases to escape during charging; see also the related requirement for vent caps in 1917.157(m).

Adequate ventilation must be provided during battery charging according to 1917.157(h).

• "Adequate" means enough airflow to prevent buildup of flammable gases (e.g., hydrogen) and to protect workers from inhalation hazards.
• Employers should evaluate charging locations (enclosed spaces, vehicle holds, or confined areas) and supply mechanical ventilation or conduct charging in a ventilated designated area as required by 1917.157(b).

Facilities for flushing the eyes, body and work area with water must be provided wherever electrolyte is handled, except when employees are only checking battery electrolyte levels or adding water, as stated in 1917.157(i).

• For handling or transferring electrolyte, provide readily accessible eye/face wash and drench showers and train staff on their use.
• OSHA's interpretation on first-aid requirements notes that some maritime standards require on-site first-aid-trained individuals and discusses first-aid readiness; see the First aid and bleeding control letter of interpretation for additional context on first-aid expectations in maritime settings.

Carboy tilters or siphons must be used to handle electrolyte in large containers, per 1917.157(j).

• Using tilters or siphons reduces the risk of spills, splashes, and manual lifting injuries when transferring corrosive electrolyte from large containers.

Battery handling equipment that could contact battery terminals or cell connectors must be insulated or otherwise protected according to 1917.157(k).

• Examples include insulated lifting bars, insulated spreaders, or insulated tools to prevent accidental short circuits and electrical shock.
• Inspect insulation regularly for damage before use.

No—metallic objects shall not be placed on uncovered batteries as required by 1917.157(l).

• Placing metal tools or parts on battery tops can create a short between terminals and cause sparks, overheating, or fires; keep work surfaces clear and use nonmetallic trays or covers if needed.

Yes—vent caps shall be in place when batteries are being charged, per 1917.157(m).

• Note that vent caps must be in place but vent holes should remain open so gases can escape, in line with 1917.157(g).

Both requirements apply: vent caps must be in place while charging, and cap vent holes must be open, as stated in 1917.157(m) and 1917.157(g).

• In practice, keep the vent cap (the removable cap assembly) installed but ensure its vent openings are not clogged so hydrogen and other gases can safely vent away from the battery during charging.

Yes—chargers shall be turned off when leads are being connected or disconnected according to 1917.157(n).

• Turning chargers off before making or breaking connections reduces arcing and lowers the risk of sparks near potentially flammable gases.

Installed batteries must be secured to avoid physical or electrical contact with compartment walls or components as required by 1917.157(o).

• Secure mounting prevents vibration damage, accidental shorting, and contact with sharp edges or moving parts; use appropriate fasteners and insulation or spacing as needed.

The ground lead must be connected away from the vehicle battery and vent holes must be open to reduce the risk of sparks and to allow gases to escape safely, as explained in 1917.157(f) and 1917.157(g).

• Connecting the ground away from the battery minimizes the chance of a spark near hydrogen that may be venting from the battery.
• Open vent holes prevent gas buildup that could ignite if a spark occurred.

Battery charging must be done in employer-designated areas and with adequate ventilation; enclosed or poorly ventilated spaces are not acceptable unless the employer provides adequate mechanical ventilation, per 1917.157(b) and 1917.157(h).

• If charging must occur in an enclosed space, the employer must ensure sufficient ventilation to prevent hazardous gas accumulation and meet other charging-area controls.

No—the requirement for facilities to flush eyes, body and the work area does not apply when employees are only checking battery electrolyte levels or adding water, as stated in 1917.157(i).

• For any other handling of electrolyte (transfer, mixing, bulk handling), employers must provide flushing facilities and appropriate emergency response measures.

When handling electrolyte in large containers, employers must use carboy tilters or siphons and must provide flushing facilities for eyes, body and the work area, per 1917.157(j) and 1917.157(i).

• Use tilters/siphons to reduce spills and splashes.
• Provide accessible eyewash/drench facilities and train employees on emergency response for electrolyte exposure.

To prevent accidental shorts, use insulated or otherwise protected handling equipment for anything that could contact battery terminals and never place metallic objects on uncovered batteries, as required by 1917.157(k) and 1917.157(l).

• Keep tools insulated, use nonconductive trays, and store loose metallic items away from battery tops to avoid shorts and sparks.

OSHA has interpreted that Part 1917's specific requirements may not apply to certain "designated waterfront facilities" used solely for bulk storage, handling, and transfer of liquids or gases; therefore applicability can depend on facility classification, as discussed in the Applicability to waterfront facilities letter of interpretation.

• Employers should confirm whether their operation fits the definition of a facility excluded from Part 1917 under 29 CFR 1917.1(a)(1)(i) and seek clarification from OSHA if unsure.
• Even where Part 1917 does not apply, other OSHA standards or the General Duty Clause may still require similar protective measures.

Employers must provide facilities to flush eyes, body and the work area where electrolyte is handled, and should ensure trained first-aiders are available as appropriate, in line with 1917.157(i) and OSHA's First aid and bleeding control letter of interpretation which discusses expectations for first-aid preparedness.

• Provide accessible eyewash/drench units, train designated personnel in first aid for chemical burns, and document first-aid arrangements consistent with maritime first-aid expectations referenced in OSHA guidance.