Why is our Mercedes-Benz E320 difficult to start?

I have a quick query about our second car, a 2006 Mercedes-Benz E320 CDI saloon. After a fault-free three years we have now had an alternator fail and, more recently, it is very slow to start, but only from cold first thing in the morning, Any ideas?

Asked on 23 June 2012 by NK, via email

Answered by Honest John
Logic tells me that the alternator failure meant that the battery was not charging properly and this led to the battery losing its capacity to hold a full charge. So replacing the battery should solve the problem.
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