A residence card is **not** considered a valid travel document to cross internal EU borders (Artical 21 [Convention implementing the Schengen Agreement][0]) . A residence card, togeather with a valid travel document (passport), shows you are legally in the Schengen Area. 

A **[valid travel document][1]** is defined as:

- valid for at least 3 months after the date you intend to leave **the EU country you are visiting**

You should **rid** yourself of the notion that just because there are no regular border checks **does not mean** you can travel without **required** travel papers. 

Spain has the strictest requirements in the EU: you must carry required documentation **at all times** (as apposed to others where you are required to only to **have** them).  

Any check that shows that your passport has expired will lead to problems, since you don't even have a **valid** travel document. 

Therefore allowing your passport to expire and then go to the country with the strictes rules is truly a very foolish thing to consider.

---
>**The Schengen acquis - [Convention implementing the Schengen Agreement][0] of 14 June 1985 between the Governments of the States of the Benelux Economic Union, the Federal Republic of Germany and the French Republic on the gradual abolition of checks at their common borders**   
...   
>**Article 21**   
>
>1. Aliens who hold valid residence permits issued by one of the Contracting Parties may, *on the basis of that permit **and a valid travel document***, move freely for up to three months within the territories of the other Contracting Parties, provided that they fulfil the entry conditions referred to in Article 5(1)(a), (c) and (e) and are not on the national list of alerts of the Contracting Party concerned.

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>[Passport and visa requirements][1]   
If you are a non-EU national wishing to visit or travel ***within* the EU**, you will need a passport:

>- valid for at least 3 months after the date you intend to leave **the EU country you are visiting**,
- which was issued within the previous 10 years,  
> 
>and possibly a visa.   
...    
If you have a valid residence permit from one of those Schengen countries, it is equivalent to a visa. 

This statement is based on **Article 6 - Entry conditions for third-country nationals** of the Schengen Border Code. 

The German residence law [AufenthG § 15 (2)(3)][10] quotes **Article 6** directly as a reason for **Refusal of entry**. 

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**Sources**:

- [Convention implementing the Schengen Agreement - EUR-Lex - 42000A0922(02) - EN][0] 
- [Travel documents for non-EU nationals – Your Europe - Your Europe][1] 
- [AufenthG § 15 Zurückweisung][10]
   - [AufenthG Section 15 Refusal of entry][11] 
      - the english version states **Article 5** instead of **Article 6**


[0]:https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:42000A0922%2802%29:EN:HTML
[1]:https://europa.eu/youreurope/citizens/travel/entry-exit/non-eu-nationals/index_en.htm
[10]:https://www.gesetze-im-internet.de/aufenthg_2004/__15.html
[11]:https://www.gesetze-im-internet.de/englisch_aufenthg/englisch_aufenthg.html#p0218