How did you attempt to increase the battery's SOC?

As far as EV mode on the HCH - it is in the owner's manual and well known by all who have an HCH (well - people who understand what they drive). Just go the the HCH-II forum and look for the thread "run on electric only?" - page 3 right now. It also talks about how doing this is bad for FE - unless you have a plug in charger.

It is possible that the HCH-I did not have an EV mode. I think the CA regs required it for some designation - the AT-PZEV probably. The partial zero part requires a mode that is gas free.

I believe the HCH goes from 20-80% SOC.