how to write this equation in matlab

I am trying to write this equation in matlab, so this is what I wrote, but it is always give me the minimim range

prob.Constraints.energyStorage(1) = ESS_SOC(1) == 10;
prob.Constraints.energyStorage(2:T) = ESS_SOC(2:T) == ESS_SOC(1:T-1) + (0.85/M)* ESS_ch(1:T-1) - (M/0.80)*ESS_disch(1:T-1);
prob.Constraints.soc = ESS_SOC >= ESS_SOC_min ;
prob.Constraints.soc1 = ESS_SOC <= ESS_SOC_max ;

the state of charge awalys at the min value which is 0.2 or 20%