optimum panel for 85 amp battery

[Lightspeed]

You might be asking a bit much of that battery to run a 300w inverter.

Recommendation for long battery life is to not run it down by more than 12%

Without efficiency losses ( of which there is a good deal on an inverter) your inverter will be able to be run for a max of 25 mins after the battery is fully charged.

If that's enough for you, you'll need approx. 600w generating power to replace the charge in winter months, but only 50w or so generating power in summer months.