Chris Dononion

It should be some 40-50% discount for Black Friday!

Hi PurePower
If you are discharging your batteries to 47V that is roughly a 60% DOD = SOC of 40%. = roughly 5.5 kWh. You have 1.22 kW of panels and with an efficiency of 3.5kWh (the jury is out on this figure but I am sure it is a good ballpark figure especially with an Axpert). You can produce 1.22 x 3.5 = 4.27 kWh on an average day a little short and if you consider direct consumption during the day and some inefficiency probably a whole lot short..
Before you add another string:
See if you can lower your overnight consumption  500W average is on the top end of what I would say is acceptable to be running off batteries.. Do you really need to cycle your batteries? Batteries are fairly expensive and if I lived in the city I would just keep them for backup- running of solar during the day and Eskom at night. Get a BMV battery monitor as it is a far more accurate way of monitoring your batteries compared to the SOC readings supplied by an Axpert. Get Manie's software and know what your draw is and how your system is behaving.  I have often used the analogy that not having a decent battery monitor is bit like driving a vehicle without a fuel gauge. Not having decent monitoring software can be the equivalent to driving in the dark without headlights - you can do it but it makes your life very difficult. 

I did PM Chris D last night with my Axpert Guide.
I am happy with the setting as proposed by Mark and yourself. 
My own system the battery bank is undersized at 260Ah. Chris D's system is very similar in other respects to my system but his battery bank is even smaller than mine. A major drawback is that Chris D is limited to only 10A charging whereas on a good sunny day he has the potential to be producing about 45A. Chris D needs to probably micro manage his loads to gain the full potential of his investment. I have to manage my loads but it is easier with a larger battery bank. A battery bank of 400Ah + is probably what we should be aiming at.

@superdiy has good settings above...
Axpert (voltage) settings
05 - Battery type - USE 26 - Bulk charging voltage - 58.4V (the maximum on the Axpert) 27 - Float charging voltage - 54.8V I would add:
12 = 48V
13 = 54V
29 = 47V
 
Regards
Mark

@Chris Hobson, your input is required.

According to the datasheet of the CEIL POWERSAFE NXT batteries:
Bulk charge should be at a voltage of 14.5V - 14.7V per battery => 58V - 58.8V for the bank Float charge at a voltage of 13.7V per battery => 54.8V for the bank Axpert (voltage) settings
05 - Battery type - USE 26 - Bulk charging voltage - 58.4V (the maximum on the Axpert) 27 - Float charging voltage - 54.8V The current settings etc. etc. depends on your preferred way of charging, your set-up and your application e.g. 2000Wp worth of panels, off-grid, only charge via solar etc. etc. You'll have to elaborate on the rest of the system and your application in order for us to make more suggestions.

Rule says up to 15% of Ah capacity of battery, so you can bump these to 15A. The rest looks good to me (generically speaking), though ideally you should check the specification of the batteries.
Yes. Dissimilar strings are the death of batteries, be that age, capacity of chemistry.
It's not ideal. It can be done, by carefully monitoring both strings and making sure the old string still gets a full charge, at the expense of slightly overcharging the new string. It's complicated and I can almost confidently say that you're going to break both strings if you do that. Read this for more info.
Sell it on and get new 200Ah batteries if you can.