@Newtron
Welcome to the forum, The size of inverter depends on what you want to power. A good brand would be a Samlex or a Cotek. The charge controller should be an MPPT type to get full potential out of the panels, as these are not standard 12 volt panels. The voltage is a little high and that will be lost with a PWM controller. For these panels in series I would recommend a Midnite Kid 30 amp MPPT controller. You will only be able to use 4 of your awesome 260AH LFP cells to make a 12 volt battery. I think 5 would be too high a voltage for the inverter to handle. These cells have to be top balanced if you don't use a BMS with them. Where you get the equipment may depend on where you are. Of course most places ship around the world at a cost.

Rick

karrak said:

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The two main critical functions of a BMS are

1. To balance the individual cells to the same SOC, lead acid batteries can do this autonomously, lithium ion batteries cannot
   

I believe that for Lead Acid batteries, an Equalizing Charge is required (in solar installs) or a long Absorb, or weeks of Float cycle.
 It does not happen on it's own.  As a cell reaches full, it simply gasses and encourages plate corrosion.  But Li cells go bang.

 Charge Controllers can be configured to do the EQ automatically (bad idea if that happens the day before the cells are due to be watered) or manually as needed.

The fact that all the cells are at 3.26 does not say much about how balanced the individual cells are. See this post for more information, I suggest reading the whole thread. That voltage does says they are all around 50% full.

Your batteries will store about ~3.3kWh (3.25*260*4) of power which will give you a maximum of 3.0kW of power for one hour or 1.5kW for two hours.

You need to know the amount of power your loads need and for what period of time, you mentioned lights, musical amps and speakers. How much power does all this equipment need in kW and how long will it be running?

The other thing you need to know to work out the size of the inverter is what is the maximum surge current that the inverter will have to supply. The start up surge current of an AC motor can be up to ten times the current needed when the motor is running. What type of power tools will you be using? If it just a normal portable drill or small circular saw I would think a 1500W inverter would be sufficient. If it is a bench saw, welder or other equipment a more powerful inverter will be required.

AC motors do not like modified sine wave inverters. I think it is worth spending the extra money on a pure sine wave inverter.

You need some sort of BMS to keep your battery balanced and make sure that all the individual cells stay in their safe operating zone, have you done any research on this?

Other equipment you will need besides the inverter is a couple fuses, one between the battery and inverter and one between the battery and charge controller, this Blue Sea Fuse block that fits on the battery terminal is a good choice.


Simon