EcoFlow Delta PRO 6+ months review

_THE DEADLY ERROR 121_

“OMG! I was out of the house and just now came back and saw the room where my first DP is with message CODE 121 OVERLOAD and smell of electronic smoke. Turned it full OFF and then turned again and it turns off by itself. Everything is disconnected but my DP is toast…… HEEEEELP!!!!!!!!!!!!“

This was the text I sent on the 9th of June 2022 to Gloria Yang from Ecoflow after coming home and smelling the carnage. At first I was shocked that this could happen and as I was trying to ventilate the room to get rid of the pervasive stench of fried electronics I suddenly felt sad and worried that this could have been much worse.

A distrust feeling started to sink in (what else could have happened when I was away…?) but I have to stress once again that thanks to the professional help of Gloria Yang I got TOP NOTCH support from her which dispelled my increasing doubts about the Ecoflow brand. She took care of everything, asked specific logical questions and reassured me that she would personally take care of everything so I could have a replacement unit (brand new) asap.

So after a couple of weeks I received the new replacement Delta PRO which I named “BALROG” (hopefully it will survive for longer than MiTHRiL).
That long of a downtime is worrisome and unacceptable to me, more so when they use a slow shipper to send the replacement Delta PRO that took 2 weeks to deliver with almost no tracking info while sending UPS PREMIUM to pick-up the broken Delta PRO that was delivered within 24h to Germany… As a customer I’d prefer the opposite to what happened so let this be a warning to what could happen to you, time wise, if you live in Europe.

This happened to me because I had my first Delta PRO (MiTHRiL) connected to my (1 week new) second Delta PRO (MORiA) in AC so as to overflow solar production from MORiA to MiTHRiL when MORiA was almost full as mixing the two PV strings in parallel would trigger the 1.285W limit and increase the MPPT controller temperature. Normally it would be a suboptimal approach to moving energy around except when it’s June and you have PV overproduction. Anyways, for all purposes and intents, in this specific mode, EPS was actively running (MORiA –AC–> MiTHRiL –AC–> ROOM). I had this setup intermittently running for a couple of days when Error 121 struck and fried MiTHRiL so, as you can deduce, it was Delta PRO MORiA running FW 0.1.0.0 that “FRIED” Delta PRO MiTHRIL running FW 1.0.85.0 and not some sketchy/bad external power source so MORiA triggered the fatal flaw within MiTHRIL.

It seems there’s always a silver lining as BALROG has newer hardware revisions of the INVERTER and MPPT controller.
The MPPT controller went from V1.0.3 (2021-09-28) to V2.0.1 (2021-11-18) and the INVERTER went from MR500-PSDR V1.0.3 (2021-08-17) to V1.0.4 (2021-01-17) (I would presume there’s a typo in the date and maybe it’s 2022-01-17 or 2021-10-17 ???).

I personally haven’t noticed anything out of the ordinary between the two versions compared to what I had (by checking against all the data that I had collected for MiTHRiL) but I want to think that R&D must have improved something.

It seems there’s a lot of people that have reported error code 121 on the forums with the same identical outcome and replaced units. Some customers have had their units replaced 4 times which blows my mind… It is a serious & costly issue that needs to be fixed asap by Ecoflow R&D.

Here’s what I’ve uncovered so far:

• It happens ONLY when in EPS/PASSTHROUGH mode so if you never use this mode, you are safe.
• It doesn’t matter what kind of load you’re running as internally the DP has triggered a relay to the mains; remember the inverter can charge or discharge but not both at the same time so in EPS the inverter is charging.
• It seems the inverter is sensible to voltages > 240V (my unit is EU) and it can have issues when there are voltage spikes.
• It also seems that sometimes the inverter might get confused and switch from charge/discharge/charge too fast and end up with magic smoke. This has been discussed and brought forward by other customers here (in my comments section) and the theory goes that the EPS mode is switching internally too fast but in stages so some of the electronics are left in the wrong setting and end up breaking.
• It seems it has been happening since the very first FW version 0.1.0.0 but the error code was different. I actually remember one case reported early on when the first US Kickstarter customers started receiving their units, someone reported that his Delta PRO went up in smoke but we all thought it was due to bad/unstable mains as the customer reported that when it happened there was an electrical storm. The symptoms he described are exactly the same as the dreaded error 121.
• It seems that it got worse after FW updated 1.0.0.74 where some customers reported slower EPS switchover speeds and same issues.
• It seems it is not fixed yet as of latest available firmware for the Delta PRO 1.0.0.96 released on the 6th of July 2022 (latest as of this writing) as multiple customers with .96 FW have got the ERROR 121.

For more insightful info reported by customers with issues I recommend you check the other articles on this site and read the comments section.

As for my take, I think the EPS implementation in the Delta PRO is poorly executed, dangerous & a useless gimmick as it has very high switchover time (30ms+), it is wasteful when running as it drains a minimum of 20Wh from the battery and has the added problem of the deadly error 121.
Some folks ask if they can substitute their UPS for the Delta PRO, especially for computers and delicate electronics and my answer would be ABSOLUTELY NOT!!!!
It is not a UPS nor can it function as one even without all the issues it has and if someone tells you otherwise then assume they are ignorant or worse.

We finally have official confirmation of what causes ERROR 121 from Ecoflow

“The error code 121 appears because when the inverter switches back and forth in EPS mode too often, the temperature of the PSDR board is too high, and the MOS tube is burned. But the latest firmware optimizes the problem, so please make sure to update your firmware if you haven’t!“

• The MOS tube is a semiconductor that can be used as an electronic switch (this is the component that changes the inverter from charge to discharge)
• The PSDR board is the inverter/charger board (one board with dual function).
• The problem is still happening with FW .96 that is the latest available since 6th July 2022 (3 months since date of publication…).
• The only way to “optimize” this problem is by crippling even further the EPS “use as a UPS” function by deliberately increasing the switchover time which renders the EPS an absolute useless gimmick; they might as well disable it completely but I think that would open up a can of worms (?)…
• This proves that having an inverter that has dual duty “charge/discharge” is not the best solution as it is fragile, tricky to implement correctly and prone to breakage from external factors like voltage fluctuations of micro-cuts from unstable utility company or AC power source.

TLDR; do not use EPS mode (plugging the Delta PRO to the wall while powering AC devices plugged to the Delta PRO “like a UPS”) at all if you want to avoid the very high chance of frying your unit’s PSDR board and having to (possibly) deal with a long downtime while waiting for an exchange unit.
I would rather have a switch in the app that disables the EPS functionality than having to deal with another error 121. My own way of disabling EPS is by never ever plugging the DP to AC when powering AC load and only charging from solar (DC) so as to use two independent circuits/boards.

PS: While writing this section I thought of a way to completely fix the “MOS Tube switching back & forth many times in EPS mode“; have a cooldown timer that will trigger when MAINS AC power is lost and inverter is switched by the MOS to AC OUTPUT (EPS mode 30ms+) so it will not let the unit switch back to MAINS AC until the cooldown timer has expired (say 1+ seconds). This way you will avoid the problem of “multiple MOS switching” while retaining the original EPS functionality as no one cares if the Delta PRO takes a few seconds to switch back to MAIN POWER from BATTERY.

• We start with Delta PRO connected to MAINS-AC with AC/INVERTER turned ON and in EPS/PASSTHROUGH mode.
• We Set MOS timeout to 2 seconds (so 1 MOS switch back to MAINS every two seconds).
• MAINS-AC goes down.
• MOS timeout starts counting from 0.
• EPS is triggered within 30ms+ so INVERTER is pulling from battery now.
• After 500ms MAINS-AC is back.
• MOS timeout check is FALSE as 500ms < 2000ms so refuse to switch back to MAINS-AC.
• When MOS timeout > 2000ms then trigger back to MAINS-AC.
• If the MAINS-AC goes down a few ms after MOS has switched to it, repeat the same sequence; worst case scenario is 2 short switches every 2 seconds.

Of course, this can only be achieved if the MOS behavior can be controlled via software (internal ESP-M ?).

_MISC/OTHER_

After waiting for many months for Ecoflow to fix the MPPT issue where the controller would limit itself to a maximum of 1.285W when voltage exceeds 125V I gave up and decided to get a second Delta PRO so I could have 2 x 1.600W with 2 independent PV strings and therefore break the 1.285W limitation and increase my daily PV production which I hoped would get closer to 2.800W out of a theoretical maximum of 3.200W and as an added bonus, double my battery capacity which was starting to be very limiting factor as, sadly, 3.648W is not remotely enough when the sun goes down and you have to run the AC a few more hours. To this date, nothing has been done to rectify this issue and I presume it will never be fixed as Ecoflow is now focused on new upcoming flagship products but I would be very happy to be wrong!

I’m glad to report that this dual Delta PRO with 2 independent PV strings has been working great and I’ve seen production as high as 3.240W 😀
I’ve modified the initial project to include a dual ATS so when one Delta PRO’s inverter goes OFF the ATS will switch over to the second Delta PRO as I want to ABSOLUTELY AVOID running in EPS mode at all costs. I have my initial “slow” ATS that has Delta PRO as primary source and utility company as secondary/backup. The “slow” ATS Delta PRO connection is connected to a “fast” ATS that has both Delta PRO so everything is automated. I can switch from one Delta PRO to the other very fast without disturbing the “slow” ATS and in case both Delta PROs are OFF then the “slow” ATS will switch over to utility company. I have this setup just in case as I’ve been running this room off-grid 95% of the time on a 24/7 schedule for the last 9+ months (as of this writing). The peak PV production was above 20.000W per day in July. All in all, since getting the first Delta PRO back in January 2022, the total solar production has been > 2.400KW and counting which is not bad at all taking into account the insane prices we’re suffering in the EU.

Another thing I had to deal with and fix myself was the absolutely HORRIBLE & UNBEARABLY LOUD noise the 4 Delta PRO server grade (high pitched super noisy 4.000+ rpm 4W each) fans produce… Now imagine TWO Delta PROs running full bore in the same room… madness!!
How loud is the Delta PRO? Well according to some, it is as loud as a normal PC with a GPU card… (What ??!!)
Well the reality is that it is as loud as having a DJI MINI2 drone hovering 20 centimeters above your head. It is THAT BAD and if someone tells you it is not loud then they need to go check their hearing ASAP!

My initial testing confirmed that the Delta PRO does not use a temperature controlled variable speed fan setting but rather a fixed 4 state (OFF/LOW/MID/HIGH) fan speed controlled by WATTS coming in/out of the INVERTER and/or MPPT controller. Yes, you read this right, controlled by watts and not temperature. To make matters even worse, the logic that controls the fans has a few notable bugs; sometimes when you are running above 600W inverter and then you go down to 80W the fans will get stuck into the MID position forever. The only way to fix this is to turn off the inverter, wait a few seconds for the fans to turn off and then turn on the inverter with the same 80W load and you will see that the fans will not turn on. As I have access to ALL the internal data of the Delta PRO (since mid January 2022), early on I already knew that it was not a temperature issue but a bug in the fan management code. Another funny bug is when you have the inverter on with something like a steady 90W load and you leave it like this for a few hours, like for the night. The Inverter (and on a lesser extent the metal box) of the Delta PRO will reach 79c but the fans will NEVER turn on and that’s the “new electronics smell” that some people reported early on for the first week of use (me included).
The thermal/fan management is some of the poorest implementation I’ve ever come across so I had to take matters into my own hands and fix the issue by redesigning the cooling system to be SILENT and MORE EFFICIENT than what stock Delta PRO has. As you can check by yourselves, I’m happy to report that my solution has been working 24/7 for months with lower temperatures compared to stock Delta PRO and a LOT quieter (38db @50cms MID) . Even when the Delta PRO is running the fans on MAX, you hear a rush of air going through the vents instead of that high pitched obnoxiously loud noise that would drive anyone crazy.

_FINAL VEREDICT_

After everything you just read, you might have formed a bad opinion about the Delta PRO but in my case I still ADORE my Delta PROs and think it is a ground breaking portable power station that I depend on 24/7. It is very hard to bring to market a complex bit of technology in such a small form factor so I applaud Ecoflow for being one of the fearless pioneers in this field and I hope to see many more new devices from their talented engineers & designers.
I’m hopeful that once the Delta PRO 2 drops, Ecoflow will have fixed all the outstanding issues and then some! (although it will be a bitter-sweet moment as I have already spent my money on the Delta PRO 1)

For sure I would have appreciated more transparency from Ecoflow when talking about the specs of the Delta PRO so I (and everyone else) could have designed a proper PV system around the Delta PRO and not have to find out about the shortcomings (I’ve describe in my articles) that forced me to spend more money and redesign the whole project around these shortcomings.

Knowing what I know now, I would still have bought the Delta PRO as I haven’t come across anything in the market that can challenge it (at date of publication).
It is versatile, portable, powerful, beautifully designed, has a ton of connections and can fit in many different scenarios where you need to bring THE POWER to power your life! ,-)

My Delta PROs have been literally “Powering my Life” every day for the last 9+ months exclusively through solar production! 🙂

Stay tuned for my upcoming article about the Delta PRO Extra Battery!