title: Pyomo - Gurobi Persistent - Change parameter values between solve
body: <p>I'm actually trying to use Gurobi in persistent mode with Pyomo.
  I've modeled (using pyomo blocks) an energy system with a battery and solve the energy/power balance at every time step, updating the battery SOC_INIT before each solve.
  It works fine when I use gurobi in none persistent mode.</p>
  <p>With gurobi-persistent, I update the SOC_INIT param and resolve. Nothing happens, the solver does nothing, and keeps all variables values from the previous solve.</p>
  <p>Roughly, What I have:</p>
  <p>The SOC_INIT Param is mutable</p>
  <p>SOC = SOC_INIT + Energy exchange during timestep (SOC is a Var)</p>
  <p>I've tried the solver.add_var/solver.update_var on SOC variable, changed SOC_INIT from Param to Var.</p>
  <p>What am I missing ? Documentation about this is not very helpful...</p>
  <p>Would someone share a proper way to do that, i.e, updating some Params/Vars between solves ? a code snippet would be nice :)</p>
  <p>Thanks for your help.
  Max.</p>