On my previous Mondeo TDCI, I had a similar issue with the glowplug light flashing plus loss of power. Unfortunately for me an injector had failed which meant a bill of £250 for a new injector fitting. Do you have excessive white smoke from the exhaust?. If so, then i would suggest you get the injectors tested. Also, when an injector fails, the car reverts to "limp-home" mode which manifests itself as the glowplug/coil looking light (as you describe) flashing. This makes the engine difficult to start, much reduced acceleration and performance. If i were you, Id get a diagnostic check done asap. Best of luck.

You need to check the battery voltage when the engine is running, should be above 13.5 volts. It might me that the alternator has failed & not charging the battery. If the voltage is good but battery is still dead you will need a new battery.

Its amps not volts that are important in car batteries.