I purchased two Smart Extra batteries, one for each EcoFlow Pro unit. I am very please on how the extra batteries add time to our power outages. The extra battery on each unit has given us an extra two days of power, running the basic needs for our home.
This was the second Delta Pro Smart Extra Battery I purchased. I began with one Delta Pro and Extra Battery for our travel trailer, as it provided 30 amp, 120V power for boondocking. After I added a 240V hub and second Delta Pro, I needed to balance battery capacity for both 120v legs of the 240V connection to the house. This battery arrived the day prior to a 24 hour power outage. The two Delta Pros (with two extra batteries) provided all the power we needed to keep refrigerators, gas heat blowers, internet, TV, and lights running for 14+ hours. A gas generator powered the house AND FAST charged the EcoFlow components in about 5 hours. I love this setup -- smart app helped me keep an eye on usage and charging status.
We have been using 2 Delta Pro and had an extra battery for each. As we Solar powered those, we realized we needed an additional battery. We are thrilled with performance and ease of use. We use them continuously and have reduced our power bill to 1/3 of what it was a year ago.