The latest information I have says that for li-ion battery packs you want to keep them charged between the range of 20-80% to maximize battery life.
Design News - News - Can EV Batteries Last 20 Years?
So a way to arrive home with about 20% left and a slow charge (slow also extends life) to 80% seems to me to be ideal. That would be about 60% of 1.4kWh or 840watt hours. A 200W charger I think wouldn't be that expensive.
Now there already is a couple of charging electronics designed in every c-max. The braking regenerative recharge system and the ICE driven charger. (At this time I'm not sure if they are actually the same). But if we could use those circuits that must already be conditioning the power to charge the battery then the 120V charger might not be that expensive. Anyone know where an electrical diagram of the CMAX could be downloaded?