I am unable to determine the exact amount of workspace that needs to be blocked off while working on battery chargers from the provided documents. However, here is some general safety advice regarding battery charging:

• Competent Persons: Ensure only competent persons change or charge storage batteries 1, 16.
• Proper Ventilation: Battery charging should occur in well-ventilated areas to prevent the accumulation of flammable gases 1, 16.
• No Ignition Sources: Keep the charging area free from ignition sources, prohibiting smoking or open flames 1, 8, 16.
• Protective Equipment: Workers should use acid-resistant gloves, aprons, and eye/face protection when handling batteries or electrolyte 1, 3.
• Emergency Procedures: Have emergency equipment and spill cleanup materials readily available [1], including facilities for quick drenching of eyes and body within 25 feet of battery handling areas [2].
• Designated Charging Areas: Battery charging should be done in designated areas 3, 8.
• Equipment Protection: Protect charging apparatus from damage 3, 8.
• Proper Procedures: When charging batteries, ensure vent caps are functioning and kept in place to avoid electrolyte spray, and battery covers are open to dissipate heat 3, 8.
• Neutralization: Provide facilities for flushing and neutralizing spilled electrolyte 3, 8 and ensure spills are cleaned up immediately 1, 4, 16.
• Signage: Post warning signs prohibiting smoking or open flames at the entrance of the charging area 1, 16.
• Non-Sparking Tools: Use non-sparking tools when connecting or disconnecting batteries [3].
• Securing Batteries: Ensure storage batteries in use are adequately secured [4].
• Electrical Safety: Ensure sufficient access and working space around electrical equipment for safe operation and maintenance 5, 7, 10.