I bought the extra battery after I added a couple of 400 watt solar panels. It definitely charges, but no second fan which is a relief. It is important to update the firmware on the app for the latest algorithm as to how the two batteries discharge. It is a complex task deciding how much juice from the second battery when the first battery has a load. It seems like a lot of times it is about half. When charging that is the case and when running my microwave if definitely draws from both batteries. The percentage full display on each will never be the same and I recommend setting your delta pro with minimum and maximum charge settings (like 5%-90%). If the delta pro runs down to zero I don't know if the extra battery work in the most efficient manner.
I bought this on Christmas Day. It is performing perfectly.
I have only two complaints. While it is well known that the documentation for the Delta Pro and the Smart Panel are limited in details and usefulness. The Delta Pro battery has taken it one level lower by not providing any documentation at all. I guess it’s hard to find fault if it doesn’t exist. Sneaky.
I am also disappointed in the fact that an interface cable isn’t provided and it’s not recommended when you order the battery, even though the battery is useless without it.
I really like the Delta Pro extra battery but it has no inputs. How hard would it be to add some functionality and it would even look better? The battery comes as advertised. I would still recommend this extra battery to a friend because it is awesome. The charge rate is very fast (about two hours from one third charge). The price is right and quality is outstanding. It is super easy to use, my 8 year old grand daughter had it up and running in no time. Even my wife thinks this is cool. The product reviews just don't do it justice. I compared it to the other main players and they just did not add up. BLUETTI didn't even come close when compared to ECO FLOW DELTA PRO! I live in Albuquerque New Mexico and we have lots of sun here so I also bought two solar panels and that's the main way I keep these two bad boys charged (my ECO FLOW Delta Pros).
I have tested my EcoFlow Delta Pro and Smart Extra Battery and I am happy with results. I ended up purchasing an addition Extra Smart Battery, so now I have 2. My only concern is the EcoFlow Pro and Smart Extra batteries are not balanced and do not discharge evenly. I have charged to 100% and then depleted to 0% as recommended to alleviate this issue, with limited results. When my additional battery arrives, I will try again. Right now the discharge difference is roughly 10%.
I have lived on boats and I am accustomed to using battery power and power management. When I saw what EcoFlow had produced with the Delta Pro I bought one, an extra battery and solar panels. I live in Florida and deal with power outages because of summer storms and hurricanes.
Now during a power outage I can sleep without the noise of a generator. Run the EcoFlow at night and charge by solar, assisted by my generator during the day.
I purchased the Delta Max in 2021, and late 2022 I got the the Delta Pro and the two batteries last month and I am planning the purchase 1 more set next month. That says a lot!