I have brand new box, used a handful of times. I was charging it these days with sp120 and was supposed to arrive to 83-85% today based on the other days. All of a sudden i checked speed of charging and was zero, because was 100% charged which would be impossible. In theory if it’s like a litio batter should have been much longer, but anyway it did a ‘jump’ of at least 15%… Is that normal? Furthermore I started using it connected to a wash machine and was going to around 1700w of load. One percent wasn’t decreasing in 33 max 35 sec instead of 42-45. Is this 15 % missing ?
The SOC “jumping” happens to me too. Note that the SOC estimator is not very accurate and sometimes it corrects itself by doing the “jump”. That said, I think the capacity is pretty spot on. I have checked it on my unit. If you want to check I would suggest you do a full discharge with a known load, like a heater or something. If you know the wattage you can estimate how long it will discharge and compare it to the “real” measurement. Note that you have to consider at least 10% in inverter losses, so I would start my estimate with 2048x0.9=1843Wh. So if you were loading the unit with 1000W you should see approximately1843/1000= 1.84hours of discharge, as an example, if you started at 100% charge.
I have also heard that the estimator may be calibrated by doing a full discharge followed by a full charge, that may minimize the jump you see.