Doran EXOPT308 Internal Rechargeable Battery Providing up to 60 hours of continuous use
Savina Ventilator-Internal Draeger Medical Medical Battery (12V 3.5Ah)
2pcs NITECORE 21700 Li ion Rechargeable Battery NL2140 4000mAh 3.7v / 14.4Wh Internal Safety Flashlight Battery|Portable Lighting Accessories| - AliExpress
Mighty Max Battery 12V 18AH SLA Internal Thread Battery for ES1230 Rechargeable Sealed Lead Acid 12180 Backup Power Batteries in the Device Replacement Batteries department at Lowes.com