Hi all, just wondering if anybody can help?

I have a 54 plate mondeo 2.0 tdci. However this morning all the electrics cut off but the engine continued to run. The electrics flashed back up on tick over at a junction etc but went off again as soon as i revved the engine. I got home, popped the bonnet and the battery was steaming like mad, figured it was nackered so just been and bought a new one. I have fitted it and when i turn on the ignition everything works fine until i fire up the engine, then after a second or so all the electrics vanish and go blank. There is 14v across the battery so i know its not the alternator which coincidentally was only changed 2 months ago anyway. I have thumbed through google for a good hour or so and cant seem to find anything about it. Can anybody help please??????

Another thing i have just noticed, if i turn the engine on, then turn everything on ie windscreen wipers, air con, de-mister, full beam etc, the dials and lights on the dash come back on but with the engine warning light (not the glow plug one). Its like something cant handle the charge from the alternator and is preventing the power getting to everything except when everything is running. is there some kind of relay or something that might be gone, or is there some way the smart charge system might be interfering?

Just tried it with alternator disconnected and everything works fine. Reconnected alternator and tried again, was fine until the battery reached full charge again then everything turned off like before

what type of battery did you fit? lead acid? lead calcium? etc..