LeonT

No equalisation required for LiFePo4
 

More investigation on this topic:
When the device is in battery mode - ie, no input at all from PV or utility and running on batteries, the fans switch off during low loads. (my tests were under 15%) Keeping the load constant, I found that the internal temperature of the unit did not surpass 42deg C. The fans did not come on at all.
I dropped the load to minimum - 0% - 1Ah - and found the internal temperature drops further to 37deg c where is sits happily. I left the unit like this for about 24 hours, and the fan did not come on at all.
So far, the fans are only constant during the charge and float of the batteries, and internal temperature above 40deg C.. (both PV and utility) 

I’m not sure on the mecer, I have a clone Axpert the moment it picks up pv solar early morning it beeps and starts charging batteries even if it’s switched off, then again late afternoon when pv is gone it beeps again and then goes to sleep.
It has a alarm ‘on and off’ function but the fans remain the noisy problem.
I once had my inverter inside the house and when it operated on batteries during the night it sounded like having a robot in the house. The fans would rev up and stop and do it’s own thing. The inverter has a silent function when the load is below I think 80Watt than it was completely silent but whenever someone in the house switched on a light somewhere it would rev up the fans. 
I ended up moving the inverter to the garage to solve the problem.
 

The fan speed control algorithm for the Axpert MKS IIs seems similar to that of the Axpert MKSs. So the fans will run at 30% minimum at all times. Fortunately, this is quite quiet, but it might be annoying in a small dwelling.
The fans respond mainly to load, both inverter load and charging load. So if you're running 75% loads, you'll get 75% fan speed, unless the PV charging is more than this, say 80%, in which case you'll get 80% fan speed. In a 5 kVA machine, the load is calculated as a fraction of 5000 VA, and the charging load is calculated as a fraction of 4000 W. So 4000 VA of load counts the same (75%) as 3000 W of PV charging.
In practice, this means that at night when there is no solar charging and the loads are light, the fan speed will be low, but not silent. The noise will mostly be during the day, when you are using loads or charging the battery, or using PV power to support the load.
So it won't be blasting 24/7, but in a small dwelling, you may want to consider a quieter option.

its interesting. on my unit when on utility power and fully charged the fans stop 
 
however on PV power .. fans never stop  even when fully charged and no load
seems to be the opposite of everyone elses 

I have a 1k RCT for my internet and the fan drove me nuts. I emailed Firstshop and they approved a return and 'fixed' it, but it made no difference.
I tinkered a bit, warranty now void, but I have not heard the fan since said tinkering. A big contributor to the noise is the mesh covering the fan, so I cut that out. I also installed a fan that runs a bit quieter, but I don't think it has actually come on yet.
The biggest problem it seems is the heatsink to which the thermal sensor is connected, it needs some breathing room... while testing the new fan I left the cover off and the fan wouldn't come on. Put the cover back and not 2 minutes and the fan is spinning like a Chihuahua with rabies. Cover off, no fan for hours.
I took the cover, removed a few bits and I can honestly say I have not heard the fan come on yet. My RCT is now a R||||. The heat sink is just to the left of the vents.

To stop the fan just use OSO under setting 16 if panels are fitted. I only use grid charge during LS.
One can also check that UTIL charge is not selected under option 16. This I belief is the same for 12/24/48V