Using data in second study w/o consulting all authors I just submitted an article using data from another study that was done together with a colleague. I am (technically) the first author of the first study, though we are equally credited first authors and we did refine the first study’s design together, though it was my idea and I wrote the software that eventually performed the data collection. I did say that the data came from our original study and cited it in the second.

He is upset as I did not ask him for permission to use the data from our joint project (I could probably still tell the journal to add him to the acknowledgements). But, he also wants to be credited as an author, even though he did not contribute to the current study. Does using data from a previous joint project warrant his authorship?
As with most authorship discussions, the issue is somewhat nuanced:


On a purely technical level, everything appears to be in order. The two of you conducted a study, and you published it together. You did a second study alone based on material from the first study, and credited it correctly. No academic misconduct has happened in any part of this process.
However, on an emotional, personal level, it is easy to see that your co-author probably assumed that you would continue working on this project together, and he feels betrayed by you taking a significant chunk from your earlier joint work and exploiting it without is knowledge, and without giving him a chance to partake and continue to get credit. Note that the issue here is not so much that he is not a co-author of a study that he did not contribute to, but that you presumably never gave him a chance to contribute and continue to be part of the project.


Edit:
Based on the OP's comments, it's not actually clear to me anymore whether the co-author did not in fact also deserve authorship in the second study. Personally, I would at the very least be highly uncomfortable using unreleased, so-far unused data that somebody else helped collect.

As is often the case, I feel it would help if you put yourself into your co-author's shoes. Would you feel that everything is ok if the roles were reversed, and your co-author just conducted this follow-up without telling you, and based partly on your earlier work and data that you collected? 

Unfortunately, it is difficult to move forward from where you currently are without any hard feelings. Adding your previous co-author to the new study, if even possible, is not ethical as (s)he did not contribute, and obviously you can't go back in time and give him a chance to continue working on the project with you. I feel an important part to clean up this situation is you apologising for not handling this situation in the best way, and acknowledging why the other side is upset (rather than focusing on whether or not you have "technically" done something wrong). If your personal situation seems salvageable, (honest) promises of joint future work usually do wonders in smoothing over rocky current authorship discussions. However, if your personal relations are sufficiently tainted, it may be best to just store this away as a learning experience and move on rather than continue working in a collaboration where the trust has been lost.