Battery Life Model for LMO/LTO chemistry

[dguittet]

Beta version of a battery life model for LMO/LTO chemistry. The model is based on test data being collected as part of BTMS, and is in-progress as the data collection is still ongoing. The final version will be similar in structure to the version in this PR, and the results will probably not change a lot. It will be published in a paper, so this model needs to be updated in the future with the reference also.

I'd like to include this version in SAM right now, in develop, in order for it to be used in PySAM for BTMS, as we're planning to start using this beta version for some analyses.

Changes:

• lib_battery_lifetime_lmolto.cpp / .h files : contains the new data structure and class
• LMOLTO option to cmod_battery, cmod_pvsamv1, and cmod_batterystateful
• Add state variables of NMC and LMOLTO battery life models as SSC_INOUTs to battery stateful
• Rename enum for life model from NRELNMC to NMC for simplicity
• Refactor daily cycle tracking state variables & functions from lifetime_nmc_t to lifetime_cycle_t for access from multiple classes
• Tests and validation against test data: test/input_cases/battery_lmolto_life/lifetime_validation_cell_1.json contains a dictionary for running the life model and expected outputs for 16 different test conditions

[brtietz]

I love the new code structure. Questions & revisions mostly deal with areas that need improved comments.

[brtietz]

Can you add a comment about which of these should be used and which should be null for each model? It's a little confusing that the cycle model pointer here isn't actually used for the nmc and lmo/lto models - is there a way to break up some of the cycle counting functions and cycle degradation functions? (that can be a different PR if needed)

[dguittet]

That's a good point. In the current code, all these shared_ptrs are not NULL even when they aren't being used, such as the lmolto pointer when using an nmc model. I added comments but also the ability to create only the sub-state structs that will be used.

ssc/shared/lib_battery_lifetime.cpp

Line 50 in cc40cae

if (model_choice == lifetime_params::CALCYC) {

That'll make it cleaner, and hopefully also clear up a little bit how the cycle model pointer here relates to the one used within the NMC & LMO/LTO models. Specifically, they are the same pointer.

ssc/shared/lib_battery_lifetime_nmc.cpp

Line 32 in cc40cae

cycle_model = std::unique_ptr<lifetime_cycle_t>(new lifetime_cycle_t(params, state));

The state created here has a cycle state that then gets passed to the constructor of the cycle model.

I'm not sure what you meant by breaking up the cycle counting functions?

[mjprilliman]

I don't have much to add. Looks good!

[brtietz]

Thanks for updating the comments and constructors!