EcoFlow Delta PRO deep-dive review

_AC INVERTER_

One unique characteristic of the AC inverter that sets it apart from competing products is it’s duality.
The clever engineers at Ecoflow have designed the inverter circuitry to have a dual purpose; it can provide a very clean and stable 230V AC 50Hz pure sine wave output (also 60Hz if needed) or it can charge the DeltaPRO from an AC source with user configurable speeds via a simple toggle in the settings tabs of the app that ranges from 200W up to 2.900W for the European version.
It’s great that I don’t need an external power brick to charge the DeltaPRO via AC but I do have to say that if the inverter gets damaged you will only be able to charge/discharge via DC.

The inverter can sustain loads of up to 3.600W (1C) without breaking a sweat and it can surge momentarily for up to 7.200W. Some people claim to be able to maintain a stable and continuous load of up to 4.000W. I reached loads of 2.400W without issues or significant voltage drops which gives me great confidence.

Come summer I will try to power a 20 year old Air Conditioning unit that puts a load of about 900W but I don’t know how high it will surge at startup so stay tuned as I’ll update this article to reflect my findings.
I couldn’t wait for summer so today (28/03/22) as the weather is sunny and hot (20c) in Barcelona, I did an initial test run of the AC (Air Conditioning) unit and I’m happy (& relieved!) to report that the DeltaPRO handled it like it was nothing!
At the time of test, I was charging the DeltaPRO via PV (solar) with around 500W/m2 while at the same time powering the whole room with around 600W.
The instant the AC engaged the load shot up to 4.5KW (so apparently inrush of around 4KW but could have been more) for a split second and then stabilized back to 1.1KW.
As I’m writing this, the AC has been running for 25 minutes without issues with a total room load of around 1.3KW.
Funny enough, the instant the AC turned on, the MPPT controller broke free of the dreaded 1.285W and has been running above that for the whole time!!
It has reached 1.6KW now with 110V * 14.3A with an MPPT temperature of 83C & Inverter 28C (I have to confess I don’t understand these numbers…!?).

A few minutes later and the MPPT BUG has appeared again; with 600W/m2 the controller locked itself to 1.285W and now the DeltaPRO has decided to drain the battery even when there’s plenty of solar energy which is BEYOND FRUSTRATING!!!…

Running the inverter (AC) will burn a minimum of 40Wh plus the conversion efficiency which I found to top at around 95% for an ideal load of PF=1 so anything below that will reduce the efficiency accordingly. It is a good conversion efficiency but once you take into account the cost of turning on the inverter (40W/h) plus the cost of running the DeltaPRO (6W to 12W for onboard electronics + 0W to 17W for fans), depending on the AC loads that you are powering and their runtime you can end up with a DeltaPRO total efficiency anywhere from mediocre to very good.

One neat trick is the AC-PASSTHROUGH which allows the DeltaPRO to act as a UPS albeit a slow one with a switching time > 20ms so I recommend to not rely on this to replace your UPS as anything sensitive like computers or equipment that can’t handle an interruption of 20ms will invariably fail or behave in unpredictable ways.
Less sensitive devices should work ok but I strongly recommend you test them before relying on it. Every single time I toggled the DeltaPRO’s pass-through, my UPS got triggered to protect all my sensible equipment.

I also experienced some very scary behavior from a dehumidifier that was running correctly on AC pass-through but once switched to battery (so AC got cut-off) it made a loud knocking noise and the power drain shot up from 220W to 1.700W which is insane as it should never go above 300W as declared by the manufacturer; I immediately turned the dehumidifier off and thankfully it has been working ok since.

To achieve AC pass-through the Inverter will turn on in a semi powered state where it will pull around 20Wh of battery to achieve 20ms+ switching time while at the same time doing a pass-through of the AC loads that are plugged into the DeltaPRO.

Of course the DeltaPRO can charge from AC, while being in passthrough and at the same time be in “pseudo-UPS” mode so it will be able to quickly (> 20ms) switch to battery mode if AC main power is down; please be mindful of the total amount of watts that the DeltaPRO can pull from your wall socket as there’s no way to configure a hard limit for the amount of watts being pulled from wall so you could end up overloading your electrical wiring or tripping your breaker.

Example:

• Two AC loads plugged into the DeltaPRO pulling a total of 2.000W
• Charging the DeltaPRO via AC pulling a total of 1.800W (config via APP).
• You plug another 1.000W AC load onto the DeltaPRO.
• Total load being pulled from wall socket where the DeltaPRO is plugged in is 4.800W or almost 21A!!! (for Europe 230V)

One extremely annoying issue that I have to endure on a daily basis is how loud the DeltaPRO gets even with very small loads.
Looking at the reported temperature of the inverter and DeltaPRO internals I discovered that the fans would be stuck at maximum speed with a temperature of 22C.

I also double checked that the exhaust air coming out of the DeltaPRO was COLD which lead me to the conclusion that the DeltaPRO’s fan control logic is not using a smooth ramp up fan speed based on temperature but a predefined set of 4 static speeds (0,1,2,3) as reported by the DeltaPRO’s “fan_state” & “fan_level” based on amps.

What is even more fascinating is the buggy code that gets the fans stuck at maximum speed even when the load drops to as low as 80W AC while other times I can manage to get around 100W AC with the fans turned completely off and the AC inverter temperature “inv/out_temp” reporting > 78C which I presume is that “smell of new electronics” that some ppl (myself included) have noticed for the first weeks of use.

Another odd behavior is when the DeltaPRO is powering 300W+ AC loads with high fan noise while on PV power (battery charging from solar < 600W + powering AC), if I switch from DeltaPRO to electrical company via ATS, turn off DeltaPRO’s AC inverter, wait for the fans to come down to almost a whisper then switch AC inverter on again, wait a few seconds (fans still whisper quiet) and then switch over from electric company to DeltaPRO via the ATS, I can power the same load with whisper quiet fans when before with the same exact conditions the fans were running at max speed.

I can easily reproduce all of the above on demand so I hope that Ecoflow engineers will fix it asap when they read these lines ;).

Please be advised that the inverter can only do one thing at a time so you won’t be able to charge and discharge at the same time via AC which means it will completely bypass the battery for AC loads when in pass-through mode.