Adding AC coupled inverter to existing hybrid setup

Hi folks,
I can't charge my batteries fully on my night time tarrif, i have 3 hours very cheap 5.5 cents (Ireland) I have a 9.5kwh battery and 5.2 and in the 3 hours especially if they are close to empty in December/Jan i can only get about 10.5kwh into them.. so about 3 short.. if i had another hour it would be ideal but failing that.. i was thinking i could try and pick up an ac coupled inverter and put the 5.2kwh battery on that and run it side by side with the gen2 hybrid i have? would they 'play nice' together? house load would be covered by both up to 6kwh? im assuming i could charge both independently then and discharge both as well? i'd put the 5.2 on the ac inverter. I guess the only hassle in cost?

michaelmcgoldrick that's a lot of effort to save 15 cents per day for a few months of the year. Change your tariff or turn up the battery reserve and hold some back for power cuts instead?

stevelewis yep... not worth it but just curious.. i was hoping there might a a relatively cheap option that i could put 3kwh into while also charging my givenergy batteries and then charge the givenergy batteries from that..