Best thing I ever did for my FFE was install an Optima D35 battery to replace the original Motorcrap battery.
https://www.amazon.com/Optima-Batteries ... B000MSDKMA
The D35 fits perfectly in the FFE battery holder.
If you can afford it, you will not regret having an Optima.
Great reference. Sadly that battery is unavailable at Amazon now. The interesting thing, Amazon says it fits my 2012 ICE Focus, but not the 2013 FFE. As WattsUp already tried this, I'd be super confident the battery would fit the FFE and work well (hard to imagine Ford putting a different battery holder in the FFE from the ICE).
Whoa, checked prices other places - $220-270.
2014 Platinum White FFE (Turning in mid Dec. 2016 25,000 miles)
2013 Ingot Silver FFE
2012 Titanium ICE Focus
2014 Tesla Model S 85