setup
Solar panels are filling accumulator by 300 kw (maximal charge rate), and at the same time accumulator is providing energy for 12 turrets and 6 combinators:12 * 24 kw + 6 * 2 kw = 300 kw.
According to this, accumulator should keep it energy at the same level, but in fact it is quickly discharging.
report
Note: combinators perform "output=input+-1", accumulator and turrets are fully charged at the start of the expiriment.If we replace six combinators with one additional turret everything will be ok:
13 * 24 kw = 312 kw > 300 kw, so turrets are slowly discharging and energy level is stable.