So I managed to deeply discharge my AGM Battery on my TDV8 2011 (don't ask), to the point where the car was completely dead with the dash lights not coming on. No problem I thought I will get out my 2000 ma Lithium Ion Battery booster and get it going again. So with the red lead to the Battery positive and the black lead clipped to a nut on top of the suspension turret, I tried to start, but nothing. Next up was a call to Green Flag who appeared promptly and using another lithium ion battery booster, he couldn't get it to start either, after much fiddling, he eventually connected the black lead direct to the negative pole of the battery, and hey presto it started, and showed a charging voltage of 13.5v.
After getting home I connected up my Ctec charger and left it to charge overnight on the Recond setting.
the question is, after such a deep discharge, is my AGM battery now toast? 2011 Vogue TDV8 4.4
1992 Mazda Mx5

You haven't done it any good but it will be fine, you have shortened it's life a bit though....  Pete
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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Due to working away this has happened to me a couple of times, charged up and all OK