High-capacity 11.1V 7800mAh Li-ion battery ensures extended operation time for Anritsu MS2721A/B, MS2723B, MS2724B, and S3x1E OTDR devices. Precision-engineered Li204SX-66A cells with advanced thermal protection for stable performance in field testing environments. Premium-grade materials and multilayer safety circuits prevent overcharging/overheating for critical measurement equipment. Direct replacement model (SM204 633-75/633-44) with exact OEM specifications for seamless compatibility. Optimized power delivery maintains instrument accuracy during fiber optic network maintenance and telecommunications troubleshooting. Industrial-grade casing resists vibration and impact during transportation or harsh job site conditions. Bulk pricing available for telecom contractors and network testing service providers.