I'm pretty sure you have enough data for the training and testing of the neural network - whether from the datasheet, or the data set that someone here gave you in another comment. Another option is to conduct some battery testing to add to your data (discharge in various currents and temperatures). But you'll still need some sensors in your system- temprature and the current drawn- those are the main paramters in estimating battery performance. Then you can train and test the model.