From the models provided from the blockset version of plecs from this link :

https://www.plexim.com/support/application-examples/976
How are the CONST I and CONSTV coefficients determined for a certain battery model in the Matlab script?

The provided example has coefficient given as follows:

%% Battery Pack controls

ConstI = 0.15*cellNominalDischargeI * n_parallel; % Target Constant charging current

ConstV = 0.95*cellFullChargeV * n_series; % Target Constant charging voltage