Missing kws, most mysterious disappearance

[janusquiz]

Hi there. I consider myself fairly advanced in electrics and have done solar for many years. Here is a situation which has me completely puzzled. I am using a solar array with a 100 amp Epever charger/controller, 50 V lithium battery bank and a Growatt 240 V inverter, hooked up to the battery (and thus the charger).

Keep in mind that the charger should put out maximum power regardless what I do since my battery bank is at a low charge rate. As the figures show, when I do not put any load on my inverter the solar panels put out about 4.9 kW and the charger puts about 4.8 kW into the batteries. When I put a load on my inverter I expected the figures to stay exactly the same. The charger does not know were the power goes, into a battery or into an inverter. Power is power. But as you can see, if I hook up a 17 and load (4.4 kW) the charger output diminishes to 3.4 kW, while it put up 4.8 kW without the inverter load. What on earth happened? where do the kilowatts go? Initially I thought it might have to do something regarding the difference in resistance of a battery or an inverter but that cannot be it because watts already is a product voltage and resistance. I got all these figures from the Epever display. The only thing I verified was measuring the AC output and I saw on my battery amp meter that power was taken out of the batteries when drawing 4 kW with the inverter (since the charger produced 4.8 kW of charge power I assumed that it would run my 4 kW load and put 800 W back into the battery, instead of draining the battery at about 20 A). And even if some of these measurements were inaccurate, fact is that my charger charges my batteries at 4.8 kW but drains the batteries when I put a 4 kW load on the inverter. Granted, there are losses, those are small and besides they are all after the charger and on the inverter side and therefore should have no bearings on charger output.

I understand that electricity gets esoteric at times but this is basic laws of physics and I just have no explanation what is going on. Kindly chime in. Thank you

A inverter load @240v	0A	10A	17A
kW inverter load @ 240V	0A	2.5kW	4.4kW
PV V output	103V	112V	118V
PV A output	48A	37A	38A
PV kW output	4.9kW	4.1kW	4.5kW
A charger output	95A	83A	70A
kW charger output	4.8kW	4.2kW	3.4kW

 

[fromport]

The only thing I can think of is some resistance in your PV supply lines.
It will try to get more power from your PV, but the amps goes down.
So if there is a bad contact == resistance in your PV supply lines, that would limit the amps.
Weird is though that the voltage goes up.
Use a infrared camera and check (as far as you can) all your wiring to see if you have a hot spot somewhere

 

[janusquiz]

Thank you for your reply and suggestion. Im not sure I understand though. Why would resistance show up differently although the load does not change? In other words, in first case the load is to charge the batteries, second case is the load goes to the inverter which is attached to the batteries? Thank you

 

[Mattb4]

You might want to do some measurements with a stand alone test meter. On my AIO's (not Growatts) I have found them to not always report accurately voltage and current. If that is off wattage reported is off.