Germany's current account surpluses: Negative effect? How to solve them? The case for a pernicious persistent current account deficit is easy to build: the home country is borrowing abroad for a long period and that debt may reach a point of becoming unsustainable. There are several ways to put pressure of the debtor to ensure repayment. The home private and government agents may self-regulate their spending, by incorporating their future expectations of what happens when their debt is no longer repayable (not likely). Another way is by market forces, if creditors think the home country is no longer able to service its debt, then funds for home will disappear, or there could be political pressure for repayment. 

However, for Balance of trade surpluses, there doesn't seem to exist any 'economic' force at work for a downward pressure... or is it?

For example Germany has been amassing enormous surpluses since the 70's, and recently, their surpluses have reach 8.5% of GDP in 2015. How does one explain this 'economically'? 

Any help would be appreciated.
As requested in comments:

German banks lost a lot of money in the US sub-prime crisis and would have lost a lot more in Greece if the Eurosystem had not saved them. This is what might reasonably be expected if you run persistent trade surpluses: you gain foreign assets which may never be repaid or may be less valuable than you expected

The European Commission is supposed to investigate under its Macroeconomic Imbalance Procedure when a country's current account surplus exceeds 6% of GDP, and Germany's is now about 8%. In the end the Macroeconomic Imbalance Procedure might in theory become an Excessive Imbalance Procedure and potentially sanctions for euro-area member states of up to 0.1% of GDP. But it will not happen to Germany, for European political reasons. Wikipedia has a description and you can also read the latest Commission report 

In effect Germany is making stuff and sending it to foreigners without exchanging it for a similar value of imports. Eventually people in Germany might notice that they could have a higher standard of living which their mercantilist politicians and economists have been denying them

German savers and politicians are already protesting about low interest rates and perhaps one day might think that in a period of negative interest rates it could be sensible to consume (and import) more