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EcoFlow Delta PRO Extra Battery review

For the past 3+ months I’ve been using the Delta PRO Extra Battery 24/7 and taking notes to write this review.

First of all I’d like to thank JON from STABLECAM and HELEN from ECOFLOW for the opportunity to do this deep dive test of the Extra Battery.


For those who don’t know, STABLECAM origins date back to 1994 albeit with a different name.
In 2017 it was re-founded as STABLECAM s.r.o, a high tech products company located in the Czech republic.

They have deep technical knowledge in all the products they sell and have always been a pleasure to work with.

STABLECAM has an annual turnover of more than 10M€ thanks to a highly integrated in-house B2B platform that manages more than 100+ pallets of goods per day from their automated central hub in Pardubice that serves all of the European market in a fast and efficient way.

STABLECAM also offers many value added services like customer support, professional manual translation, service center, training day events for partners in the newest and hottest devices like drones and they are very active at international expos, presentations and shows.


ECOFLOW started out in (November) 2016 with a group of highly experienced battery engineers who had a vision to power a new world. Fast forward to 2021 and the EcoFlow Delta PRO is listed in Time Magazine as among the 100 most groundbreaking inventions of 2021 that change how we live, work and play.

ECOFLOW has raised more than 114M$ and has international headquarters in US and China. They serve a global market of more than 110 countries and my personal experience in dealing with them has always been great and especially outstanding with Gloria Yang.


Each Delta PRO can have a maximum of two Extra Batteries that would extend it’s capacity from 3.6KW to 10.8KW. It’s an ingenious system that works very well but I do have to point out that the Extra Battery cannot function on it’s own as it needs the Delta PRO to be able to charge/discharge so if the Delta PRO unit has a malfunction, the Extra Battery would not be useable on it’s own.

The Extra Battery has the exact same dimensions and looks as the Delta PRO, which I consider is a correct choice from a design perspective, but less weight (38 vs 45kg).

The top part of the Extra Battery has a nice compartment where you can store cables and other accessories instead of the electronics box of the Delta PRO (inverter + mppt controller combo). The Extra Battery has NO fans to cool off the battery pack which is exactly the same as the Delta PRO; the 4 fans of the Delta PRO cool the electronics metal box (inverter + mppt controller) but NOT the battery pack that is below as there’s no airflow going down there.

You connect the Extra Battery to the Delta PRO through an included very thick cable that has power + data pins so the two units can communicate and coordinate their actions when charging/discharging + other miscellaneous operations. The cable needs to be very thick as the units can move up to 80 amps of current at 42V and the cable looks and feels very sturdy and up to the task but a bit short and unwieldy which complicates the placement of the Extra Battery but understandable as they need to minimize power loss as much as possible. The Delta PRO acts as the master and brains controlling the Extra Battery when charging and discharging and will try it’s best to distribute the load and balance the total capacity among them.

I also have to point out that the shape of the connector (straight, not L shaped) will force you to leave extra space behind the two units if you put them side by side (as you should while being careful not to block the Delta PRO fans!). I’ve seem some customers put the Extra Battery on top of the Delta PRO which is not advisable.

Pay attention when you plug the cable, to make sure it goes all the way in and the retention clip of the cable snaps shut. Be extra careful to unlock the pin fully when disconnecting the cable (POWER OFF COMPLETELY BOTH UNITS FIRST!!!) and take your time as it is quite unwieldly and fits very snuggly but never pull from the cable side, always from the connector (wrap both hands around the connector if you need to and don’t wiggle it)!

4 thoughts on “EcoFlow Delta PRO Extra Battery review

  • I see on your You Tube vid about fan noise that you’ve modified your Delat Pro to drop the noise to 40dB. Can you detail what the mod is? I’ve considered replacing the fans with “Arctic” brand low noise fans but would like to hear your ideas first.


    • Hi George.
      This is what I wrote on YT in respect to the fans:

      First I would encourage you not to open/modify the DP and not to obsess too much over it. In my case after 4 days of testing multiple combinations I settled for 2 Arctic with high static pressure as INTAKE and two Noctua with high volume as EXHAUST. But the thing is that the intake and exhaust are reversed from stock (intake left to exhaust right). Weird I know but the data consistently showed that it was the best combination. The data you can get it from the device wirelessly by yourself if you want to tinker and build everything from scratch or by installing and using Home Automation with DeltaPRO plugin (search the net and you should find info). I had to create adapters for the fans to connect to the non standard plugs of the DP. I chose that route so I could drop again original fans if need be. Good luck and be careful!

  • Hi There,
    I wish I had discovered your forum sooner. I purchased the EF DP in September 2022 from Amazon along with a Solar Panel (of which I am yet to use). I had been using the unit to run large appliances during peak times and charge the unit during off peak periods via AC. I use the “Slow/Custom” switch and control the charge voltage in the app. I reside in Australia. The system has 4x 230V 10A sockets along for output. Generally, I am able to operate a dishwasher at 75 degrees C (167F) for 2hrs 10 mins and a 2hr 35 min load of laundry in my front load washing machine using cold water. Then the battery would be be at 1%. I purchased the EF DP Remote Control and immediately was disappointed that the screen kept timing out at 60 secs max despite it being connected to an always on USB-C cable. I had contacted EF Support to address this, they took an exceptionally long time in trying to help resolve the issue. I had to provide video evidence of what had been occurring. They said it was definitely faulty and they would be sending me a replacement. After the replacement had arrived, I had set it up and paired it successfully with my DP and connected it via Ethernet to perform a FW update on it. I immediately noticed that the issue was still present and called them out on it. They said this time it is a limitation of the FW and there is nothing further that they could do. I still have the other EF DP Remote with me and they have not requested it back – What gets me is why get me to go through the hell of trying to demonstrate an issue with their expensive remote control when they were already aware of it?? The eventually emailed me asking if I wanted to keep it or they would refund me for the purchase. I didnt reply as I thought whats the point, I would have to post one back to them and pay for shipping.

    I recently purchased the EF DP Extra Battery for the insane price of $4369 AUD and have successfully connected it to my DP. I noticed after I had reached a charge of 100% (which both units were displaying), the app indicated a FW update was available and I updated thinking this is the correct thing to do. I am now sitting on V1.0.1.18 and V3.0.1.11 (WiFi) as displayed on the app.
    My first operation was to run a full load of laundry in my clothes dryer with X-Boost turned on, running a Dyson Purifier Fan and a Dehumidifier at the same time and I had observed the Extra Battery was matching the output of the DP of 2500W+ at one time.
    A week on using the EB I am not satisfied. The Extra Battery when in operation with the DP running the same load as before does not match any longer. The EB seems to max out at 1100W input to the DP and doesn’t assist the DP when its almost out of juice. I feel load balancing is a problem as it clearly cannot achieve this. I’ve also found that despite the EB having a higher charge remaining the DP continues to output a charge to “top-it-up” where as it should be doing the opposite and providing a charge to the DP.

    I am currently charging my DP from 43% to 100% at 2000W (the max output from my outlet is 2300W, but sometimes trips the breaker). Whilst charging it is outputting 794w to the EB at the same time and both capacities are almost identical.

    I only wish the EB would function as it was marketed to me as. I am somewhat happy with the EF DP however these FW issues are bugging me. I wish there was a was to reset back to stock FW. I have my unit connected to the internet and use it via Bluetooth when the internet goes down.

    Appreciate your thoughts?

    Thanks for reading.

    – Daniel

    • Hi Daniel!

      The EB & DP wil never be identical because of how voltage/charge transfer works.
      When charging, the DP has a higher internal (battery pack) voltage than the EB so the EB can charge from the DP and the opposite is true when discharging; the EB will have a higher internal (battery pack) voltage than the DP so the DP can take energy from the EB.
      What I’ve observerd is that the BMS (Battery Management System) will try to keep both battery packs (DP/EB) within 0.10V of each other
      What you see on the LCD as % of charge is basically a (best case) guess when the battery (DP or EB) have had a full charge + state reset (State of Charge); the computer that manages the battery has an internal table of data that correleates voltage, temperature, cycles to an approximate, user facing percent of charge that will get out of sync (looses precision) the more you use the DP but the full battery capacity is stil there just not reported correctly to the user.

      This past week, I’ve observerd an issue with my EB where after charging to 100% from solar, when disconnecting from solar, it would not share the load with the DP so the DP drained 20% while the EB didn’t budge (0 watts).
      The only way to kick it out of it’s slumber was to drastically increase the drain on the system (DP+EB) from 200W to around 1.500W which finally woke up the EB and started draining 3:1 vs the DP to try and catch up (took a long time to almost catch up).

      TLDR: It’s a BETA product that needs some nursing where you’ll have to jump in when an issue arises to fix it and go back to normal. The disparity between what is reported (%) and reality can become big with time/cycles and the only way to fix it is to reset the counter (check my articles for the 15 seconds procedure to reset it).

      As for the REMOTE, it was an issue with early FW because it wasn’t coded properly so they finally took the time to implement it and then used the DP to reprogram the REMOTE so it wouldn’t turn OFF at 60 seconds __BUT__ you NEED to have the remote connected via ETHERNET/NETWORK cable when doing the FW upgrade and when using the device or it will revert to 60 seconds.
      I have my remote via ethernet cable and it is on for 16+ hours a day since the last 9 months or so.

      Hope this helps!
      Take care.


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