Ywain

@Ywain
No matter which option, it is recommended to always use a balancer between the batteries to ensure all batteries stay at the same voltage. 
You can also use this approach (should be adapted to 4 batteries). I would just connect the positive to the opposite side of the negative:

Option A, otherwise you require double the number of balancers.

For Sale: Sunsynk 12Kw 3 Phase Inverter + SunSynk Dongle for R58,500 incl VAT

We purchase this for a client, and after completing the installation it turns out that when they thought they had 3 phase power, they in fact now have a Red / White / Blue phase in their house which is each showing 230V.  It used to be full three phase, but apparently the cable is damaged, so as a quick fix Eskom has bridged the White phase to the Red and Blue in the distribution board (disconnected the incoming Red and Blue - see picture).  As a result this unit will not sync with the grid as it is not 3 phase (voltage between the Red / White and Blue is 0V and not 380V).  We removed the unit as it would not sync with the grid and installed a Sunsynk 16Kw (single output feeding the house Red White and Blue) which is working perfectly.  The Sunsynk 12Kw 3 Phase unit including SunSynk Dongle is for sale at R58,500 incl VAT.

The unit is boxed, including all original Manuals, Stickers, Screws, Mounting plate, 3 CT's, Dongle, Temperature Probe, BMS Cable, and a 18mm Shutterboard Back Board.

For Sale: Sunsynk 12Kw 3 Phase Inverter + SunSynk Dongle for R58,500 incl VAT

We purchase this for a client, and after completing the installation it turns out that when they thought they had 3 phase power, they in fact now have a Red / White / Blue phase in their house which is each showing 230V.  It used to be full three phase, but apparently the cable is damaged, so as a quick fix Eskom has bridged the White phase to the Red and Blue in the distribution board (disconnected the incoming Red and Blue - see picture).  As a result this unit will not sync with the grid as it is not 3 phase (voltage between the Red / White and Blue is 0V and not 380V).  We removed the unit as it would not sync with the grid and installed a Sunsynk 16Kw (single output feeding the house Red White and Blue) which is working perfectly.  The Sunsynk 12Kw 3 Phase unit including SunSynk Dongle is for sale at R58,500 incl VAT.