Instantaneous control using Fuzzy logic toolbox

Hi,

I am trying to implement an instantaneous control strategy using Fuzzy Logic to control the charging of a Li-ion battery so that the discharge current is kept to a minimum. Is this possible using the Matlab fuzzy logic toolbox? The graph that I get using Fuzzy logic toolbox ie ANFIS in particular, is always a horizontal line. There are no peaks or troughs in the graph. This doesn't make any sense. Can anybody tell me if this type of control is possible and if it is possible, how?

Thanks.