How much PV/GTI power can I safely AC couple to my Powerjack without cooking the batteries/damage the PJ?
You will need to know the C10 charge rate of your AGM's, most AGM's have this written on them somewhere.
In my opinion AGM's need careful treatment, and they can not stand the abuse like FLA's, Flooded Lead Acid types.
At only 200ah and 5kW of PV, !!!!!!!!!. In my experience, and this only my experience, others will comment further, 200ah then 2kW of PV is still to much. In my opinion, with 5kW, You definitely need AC load shedding, and a charging regime.
If it were me with such a low AH batteries, I would use the AC through a standard 48v battery charger to your batteries. I can also use a 100amp Eltek charger, (thanks Simon) as I can control what amps it gives out and the precise voltage it gives. see photo below....... And at night switch over using a big 2 pole change over switch to your PJ created grid running from your batteries.
Are you switching over from Mains Grid to the PJ created Grid or are you mixing. If you are mixing then you have done well getting the PJ to sync with the normal Grid. As 'oztules' has said, 1 in 5 times you get away with it, other wise its smoke.
For the sake of sizing what % of the energy generated by PV will be available for useage at night? I reffer to losses in transitions and storage
Others on here are better informed and will probably comment.
I have 63kw of storage but its never enough, but then my house is largish and my other buildings need power.
Yes all my batteries are AGM's and all are from Telecommunication installations after the service contract has expired. So I pay a little more than scrap price.
I sort through them and take good matching strings at a time. Life time before the lead plates short out on the interconnect internal link, only 8 mm clearance by the manufacturer, for me is a usable 8 years.
I am about to add another 2 strings 210ah, (see if Simon has any), as my oldest are struggling to hold 12.80v and in another 6 months they will fail. Just my experience after 10 years.......
Your batteries will be your biggest investment, so they really do need looking after.
Eltek with mods. Eltek set for a gentle 48v battery charge. 2 Pole 90 amp Change over switch.