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EcoFlow Delta PRO 6+ months review

Please read the deep dive review article about the DeltaPRO if you haven’t done yet HERE.

I started writing this when I was about to reach 6 months of usage but then life happened and now we can call this the 9 months review 😉

How did the Delta PRO behave after more than 6 months of 24/7 intensive use?
Did it stand up to the challenges? how high of a load did it handle? Did I uncover any new issues? Did it fail?
Was I able to improve any aspect of the Delta PRO?
Would I still buy the Ecoflow Delta PRO after all the knowledge that I’ve gathered?

Please bear in mind that this review is geared towards the specifics of this project, which is to power a room 24/7 with as much solar energy as possible and only fallback to the grid if the battery isn’t enough to cover daily needs. The Delta PRO is versatile enough to be used in multiple scenarios like camping, emergency backup, powering music gear at open air festivals, radio communication gear, workshop power tools and just about anything you could think of.

Sure it is heavy on paper but “does not feel” as heavy as one would think in part thanks to it’s well engineered handles, heavy-duty wheels and telescopic arm.


The Delta PRO inverter, which is on 24/7, performed flawlessly while powering continuous loads that ranged from 100W all the way to 3000W+ with around 8 hours of 1.200W+ non stop, covered by solar during day time, battery at nigh time and never resorting to EPS (passthrough) functionality.

The biggest steady draw by far was from a 20+ years non-inverter European Air Conditioning unit that has an inrush start current (that I could detect) of around 3.000W. It has never failed me once which is very reassuring. I’ve also reached peaks of 4.000W+ for a short time with a kettle on top of what was already running. Even a hoover that draws close to 1.500W was no problem on top of what was already running (2.800W+).

All of these tests were done with MPPT+BATTERY or only BATTERY mode. I’ve installed an ATS in/for the room that has the grid power as “BACKUP” and the Delta PRO as “MAIN” so that the Delta PRO is never connected in PASSTROUGH mode and will never charge from AC/GRID.

It seems some people were complaining about their units shutting down the AC/INVERTER with “OVERLOAD” sign while using it in battery mode and from my observations I think one possible explanation is that maybe their battery pack is not as well matched or balanced as mine (?).
You have to bear in mind that the battery is as strong as it’s weakest link and thanks to my early tapping into the internal data of the Delta PRO, I was able to create a very simple formula to asses the quality of the cell-level balancing on a scale that goes from 0% (dead) to 100% (pure perfection). My Delta PRO would hover around 99.70% even under heavy load which means that all the cells of my Delta PRO’s battery pack are top quality and very well matched.
In conclusion, the Delta PRO’s inverter is as solid as they come although a bit too thirsty with it’s minimum of 40W + conversion efficiency to run but you can rest assured that in the end it can tackle almost any challenge you throw at it.


Thanks to tapping into and analyzing the internal data stream of the Delta PRO I was able to guess that the battery pack consists of 15 individual cells of 3.2V/5.3A (48V/80A) with a total RAW combined capacity of 3.840W of which 3.648W is user accessible.

A battery pack is as strong as it’s weakest link and is managed by the BMS which is the “brains” of the pack.

The BMS is tasked with multiple functions among which:

  • Constantly manage the charge/discharge rate of each individual cell so their voltage is as close as possible between them. If the voltage is identical among the different cells then we get a perfectly balanced battery pack. The closer we are to this ideal, the better the battery pack will perform in terms of battery capacity, charge and discharge, heat and general performance. The ideal is to have all of the cells in perfect sync with each other, voltage and capacity wise.
  • Protect the battery pack from undesirable situations like under-volt, overvolt, overheat, under-temp, high dis/charge rate, etc.

If only one of the 15 individual cells is weaker than it’s siblings or has some issues when there’s an instant big draw of energy it could happen that it’s voltage would dip, for a few milliseconds, below what the BMS considers to be the acceptable minimum for the cell which would trigger a protective shutdown/disconnect of the whole battery pack (overload). Once that cell recovers, everything will be back to normal. A sudden dip in voltage in a healthy power source usually happens when there’s a sudden instant high load.

The battery pack is at the bottom of the Delta PRO and has no active cooling system so be mindful to not run your unit in a very hot location as you might find that the unit will not run to it’s full potential to protect the battery/electronics. The only active cooling is the 4 obnoxiously loud fans that are on the top part of the Delta PRO to cool the MPPT/INVERTER/CHARGER metal box.

_MPPT Controller_

I consider the MPPT controller the weakest/underperforming component of the Delta PRO. After doing multiple tests and analyzing the data I came to the conclusion that the MPPT controller was hardware designed to accomplish a maximum of 1.200W under ideal conditions of 100V and 12A and that’s it, period!

I think later on, the marketing department at Ecoflow realized that the “solar” part of the Delta PRO was the lowest among competitors and pushed for an increase in numbers so the engineers at Ecoflow tried their best to push the hardware to the max by increasing the amps it could handle from 12A to 15A (16.3A in my observations) which would push it to a theoretical maximum of 1.600W in ideal conditions.

Those ideal conditions would be around 110V and 15A. The higher the volts go the higher the temps will go too. The MPPT controller has a hard limit of 125V under load which means that if the solar array is producing 126V under full draw then the MPPT controller will go into what I call “Limited Mode 1” and will never ever go above EXACLTY 1.285W. To achieve this, it will start dropping the Amps to stay at 1.285W which of course will make the Volts shoot up. The MPPT controller will get stuck in this mode for a long time even when the energy produced by the PV string drops which will waste a lot of unharvested extra watts.

One of the most weird and frustrating bugs this mppt controller has is when it is incapable of properly extracting all the watts of a PV string when in unstable/shaded conditions. The difference can be very dramatic in the order of more than a magnitud. For example, in a PV string of 3 x 540W panels in series, if one panel gets some shading, the production drops from about 1.000W to 70W because the mppt controller is incapable of scanning for lower voltage so it gives up, lets the volts shoot up and the amps drop to almost nothing but sometimes, if you connect and disconnect the PV array while this condition is happening you might get lucky and force the mppt to reset and start scanning from 10V all the way up to finally find the sweet spot of volts/amps with a jaw-dropping improvement of 820W as you go from 70W to 890W which is HUGE.

Another observation is that the MPPT controller is happiest when you provide it with a voltage that is at or below 50V. In one of my tests, I ran 3 solar panels in parallel (3P) with around 41V and 16A (the max the DP can take actually) and the internal temperature of the mppt controller with fans in lowest setting was never above 29c with a room temperature of 27c !!! Another side effect is that the conversion efficiency shot up to 98% which is great! The only negative side is that you won’t get more than 700W as you are severely limited by the AMPS capacity of the MPPT controller. In the opposite case, when I ran the same panels in series (3S) with same weather conditions and power output, the temperature was around 65c and the efficiency dropped to a max of 94% which makes sense as stepping down the voltage from 123V all the way down to 50V produces extra HEAT and that heat is wasted energy.

It would have been nice if Ecoflow was upfront about all this data from the beginning so customers could plan their PV setups accordingly.
I’d ask Ecoflow to maybe increase the AMPS intake of the MPPT controller to 20A while limiting the WATTS to a maximum of 1.600W of course. In my case, in winter and due to my location and limited space, I have a lot of shading from October until January that forces me to redo my PV strings from 3S to 3P so as to maximize my limited/low production but as the Delta PRO can only take 16A, I would be wasting some extra energy when under direct sun on a clear day so I hope for a small increase from 16A to 20A as the 3 panels in parallel could theoretically produce 40A but being winter, I would assume it won’t go above 20A. As for the VOLTS, the panels VMAX is rated at around 42V so 42*20=840W max (42*16=672W).

11 thoughts on “EcoFlow Delta PRO 6+ months review

  • It’s interesting to learn what Ecoflow claims as the cause of the pass-through EPS issue. I have one Delta Pro that is only powering my home’s fridge, and have successfully (so-far) avoided the issue by automating the twice daily pass-through switching. I.e. When it’s time to enable/disable the pass-through, the automation waits until the fridge is in an off-cycle, then turns off the Delta Pro’s AC Output before toggling its’ AC Input, followed by a delay and turning the AC Output back on. The idea is never to have the AC Output on when the EPS switch-over event is anticipated.

    Based on the explanation that the fault is related to component over-heating, I think I may be able to change it to allow an EPS switch-over only when there is zero load on the AC Output without turning off the output off.

    • I saw a Screenshot of a new firmware for the river series and Delta mini in which they remove the USP function.

        • Interesting…. Although if EcoFlow “downgrade” a product it might open them to some form of liability?

    • Well…. I’m staying put and not updating anything anymore (hence why I don’t publish new firmware articles) as I don’t want to experiment any further and risk frying another unit. Everything is working as intended for my use case (after adapting my use case to overcome all of the limitations and issues of the DeltaPRO).

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