# How are the voltage step simulations implemented? **URL:** \ **Category:** PyBaMM Q&A\ **Created:** [7 March 2025 17:32 UTC](https://pybamm.discourse.group/t/how-are-the-voltage-step-simulations-implemented/222 "2025-03-07T17:32:50Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![brian\_osp](https://avatars.discourse-cdn.com/v4/letter/b/ecae2f/32.png) [@brian\_osp](https://pybamm.discourse.group/u/brian_osp)\ **Post date:** [7 March 2025 17:32 UTC](https://pybamm.discourse.group/t/how-are-the-voltage-step-simulations-implemented/222/1 "2025-03-07T17:32:50Z")
Hi. I’ve been using PyBaMM for parameters identification, mostly using constant current experiments. I would like to use also constant voltage data, but before I would like to understand how the voltage-controlled steps are implemented. I understand that the constant voltage condition is added as an algebraic equation to the system, but I don’t see how this equation is incorporated to the rest of the model, in particular I don’t understand how the current density would be defined under this type of step. I haven’t been able to find any information on this in the documentation or in the citations. Does anyone know any reference that can provide some light to this aspect? Thank you in advance for any help. ---
**Author:** ![valentinsulzer](https://yyz2.discourse-cdn.com/free1/user_avatar/pybamm.discourse.group/valentinsulzer/32/9_2.png) [@valentinsulzer](https://pybamm.discourse.group/u/valentinsulzer)\ **Post date:** [11 March 2025 00:26 UTC](https://pybamm.discourse.group/t/how-are-the-voltage-step-simulations-implemented/222/2 "2025-03-11T00:26:05Z")
The current density is defined as a variable, then we have an algebraic equation which is `0 = f(x,z) - V_target` where `f` is the voltage as a function of the other states and `V_target` is the target voltage. It’s similar to [this paper](https://iopscience.iop.org/article/10.1149/1945-7111/ac9a80/pdf)