German auto banks

According to the Handelsblatt, German auto banks (VW, Daimler and BMW's financial arms) are being overwhelmed by new deposits. Apparently, they have started to turn new customers away, and they don't know what to do with all the fresh cash. For example, Mercedes-Benz-Bank increased its short-term deposit base from 6 bn € to 10 bn € in Jan/Feb 2009 alone. 80,000 applications to open accounts have been received but not yet processed.

It's bizarre: Their interest-rates are far higher than anything the competition has to offer (Mercedes-Benz offers 4 % on short-term deposits, VW 4.5 % for mid-term deposits), and according to the FT, they are depositing large volumes of excess cash with the European Central Bank, earning less than 2 %. Hasn't it occured to them to simply lower their rates?

(Apparently, auto banks are allowed to give loans to their mother companies, but according to the Handelsblatt, this is limited to 20 % of equity, or 190 m € in case of Daimler-Benz bank. Those 190 m € would be far cheaper funding than anything they can get on the capital market these days, but it's not really very helpful to collect billions of additional assets, because they are still limited to 20 % of their equity ...)