Does upgrading the low voltage 12v battery to a higher capacity help the MPG?

I was reading about upgrade my 2013 C-max Energi Battery can help with some problems down the road because some equipment use the low voltage battery.

http://fordcmaxhybridforum.com/topic...tery-solution/

So, I know the fan (not A/C) and stereo use electricity in my 2007 Escape Hybrid, do you think increasing the capacity of the low voltage 12v battery capacity would allow the ICE to be off more and hence increase MPG?

 

If a solution were that simple, everyone would do it. A 12v starting battery is not capable of supporting rapid charging and discharging like the 330V traction battery.
Upgrading the 12v battery only provides better starting in my experience (especially in cold weather).

 

I was not expecting a major improvement, but possibly a minor one.

I just know that when I am stuck in traffic not moving with the windows down, the ICE comes on more than I think is necessary.

 

Even that probably doesn't hold true for hybrids like the FEH, since it uses the traction battery and an electric motor to start the gas engine. As long as the 12V battery has enough juice to close the relays to connect the traction battery, it has no other role in starting.

 

With regard to the ICE coming on the system has a Hi Voltage DC to 12V DC convertor. The 12 v Battery is floating on that system so replacing it won't make much difference in on-off cycling of the ICE in traffic since whatever load there is, is actually being carried by the Hi Voltage battery. I suppose if the 12v battery were shorted and so discharging the Hi Voltage battery more quickly that might be the culprit... but then you'd have had a problem starting since the 12 v battery must close the relay.