【9 DC Outlets】Unlike competing products, the HELIOS 3600 expansion battery supports standalone discharging and can independently power USB-A, USB-C, car cigarette lighter, and DC 5521 devices. 【Expandable Capacity】The battery system is expandable from 3.6kWh to 36kWh. Each HELIOS 3600 can add up to 4 expansion batteries. At maximum system configuration, the 36kWh battery system can power your home for 4-7 days. 【Storage Compartment】HELIOS 3600 expansion battery has a convenient storage compartment on the top to keep your cables & adapters organized. 【Excellent Portability】The HELIOS 3600 expansion battery has a retractable handle and two large outdoor wheels. You can easily roll it like a suitcase indoors or outdoors. 【Detailed LCD Display】With auto brightness adjustment, the clear LCD display provides full information you need to know about the battery. * This product is specially designed for HELIOS 3600. Make sure you have purchased the Growatt HELIOS 3600 portable power station before purchasing this product separately.