Question about battery bank size

[Kragoth1]

My current main system is charging off an 1.2kw (4 pnls) array in 2s2p config, epever 4210n charge controller 100v / 40 amp powering 6 12v 100ah flooded lead acid marine batteries wired 24v and feeding into a 3500/7000w inverter

This system charges at 40amps 24v into 300ahr 24v battery bank. In its current set up I have all the power I need during day time (saws, compressor, laptop) and the batteries are actually filled pretty quickly, by 10 am they are back to float, 7 years on this system and I only take the top 20% off at night 24.8v or so when I shut down at night.

However I am not currently running items that require power 24/7 and that’s about to change, wanting to add a frig, my plan is to add a few more batteries to the sting to increase my night time power availability. ( please don’t go into mixing new and old, I am well aware)

Now onto the question
40a charger, 300ah battery’s increasing to 500ah of total batteries

Will the charger keep up?

I know there is a rule of thumb for the charger capacity vs the string capacity, that’s what I’m looking for, seen it referenced, but have looked for days and can’t seem to find the rule or formula

Trying to figure out if batteries are enough or if I need to get a 2nd charge controller and a couple of pnls and put both in 3s, 4s overdrives the pv 100v max and wouldn’t increase the 40a limit on the controller anyway,

Thanks in advance

 

[Kragoth1]

Also, I know I can dip deeper into my batteries, but thier cheap batteries, and they last a lot longer if I don’t draw them down anywhere close to the 50% mark( read 7 years on Walmart marine batts and every one of them load and hygr tests awesome still)

 

[rodrick]

If you are getting the batteries full on a regular basis by 10am you could expand the bank as long as you can recharge them to full charge by the end of the day, if not you have to add more panels, adding more load to system now may be wise to see if you can keep up with the battery needs presently and then if it works add the extra batteries to keep your discharge per battery less, if you can’t recharge the system add panels first

 

[Hogheavenfarm]

I would experiment with a load at night, I usually use lights, as they can be modular, adding additional lights to increase the load and watch the recharge times. That will tell you have many watts you can add and still reach a full charge.

 

[MaikaiLifeDIY]

I presume this can be estimated with a calculation. If you have 500 amp hours, and you use 200 of them, at a maximum of 40 amps charging it would take 5 hours to recharge those batteries back to 100% assuming no loads are consuming some of your maximum 40 amps charging capacity. As the other users mentioned, running some lights to test your theories on run time would be a perfect way to simulate what the estimated impact would be when you add the fridge.