Since you did not give the size of your batteries I will let you do the math. A safe charge rate is .5C
It depends on the fixture or the bulb. Lumens per Watt vary a lot between LEDs. There is a sweet spot between Lumen output and current but unless you have an LED driver that can vary the current and a good light meter you would never know. The actual voltage at the LED is only 3 volts so either way there will be conversion losses.
You did not say what the amp hour rating was for your batteries but 65 amps divided by 4 is 16.25 amps it would have to have a pretty small amp hour rating to have trouble at 16 amps.
Multiply your amp hour rating by .5 and in your case you wold get a max charge rate of 50 amps per battery since you have 4 in parallel your theoretical max charge rate woul be 4 times that or .5 times 400 ah of battery.
Keep in mind that no matter how quickly you are able to charge those batteries initially they will slow down to a crawl once they get to about 80% charge and it will take 4 to 8 hours to fully charge them after that.
So you’re saying that its more efficient to run what I can on 12v?
charging Amps for LFP is typically 0.5 times the Amphour capacity. I don't know what the rate is for Flooded.
As soon as you start using 110v items your power usage will go up exponentially. I think that’s psychological more than anything else somehow it is easier to be deliberate about 12 v devices. Also all inverters have a efficiency loss and idle consumption so it takes a noticeable amount of additional solar power to run a 24/7 inverter system than a 12v only system with the same wattage loads. It really depends on where you want to compromise when you setup your system. I think the best compromise is to have a inverter available for what you need but only have it on when you need it. With only 4 fla batteries you will need to be very thoughtful about your power usage unless you only have the smallest of loads. I started with flooded lead acid batteries because it was all I could afford and they do work but it is an art to get them fully charged on a system that you are using. They have to be maintained especially if you are pushing the acceptable charge rate. They also are heavily affected by the Pukart effect which means the faster you use the power from the batteries the less power is possible to use. Also they have poor faradaic efficiency only between 60 and 80% of the energy that you put into the batteries will be available to use when you are finished charging. All of these factors become exaggerated as the batteries get colder but “hot” batteries deteriorate very quickly so it’s a real balancing act to make the most of them. With only 400 ah nominal of fla batteries to play with you will need to be very thoughtful about your loads.
