Giv energy 3.6kw Gen 1 Inverter not charging properly

Hi I Have a 3.6kw gen 1 inverter, the settings for the inverter allow a maximum charge and discharge of 2600watts, however during the charging cycle on off peak electricity the maximum it charges is 2424watt per hour. Is this normal or is the inverter faulty. thanks

Could just be due to the difference between AC and DC measurements?

Or could be weather related if it’s in a garage?

(If it was outside I’d assume it’d charge much more slowly than that given the current weather)

I have just run a test on my Gen1 battery in garage at 2 deg C, and it charged from grid at 2425W. It may relate to state of charge of battery [3%] or the temperature, or it just is. Had a quick look to find a sunny day last summer [there seemed to be fewer of them] and found a time where the charge was 2494W