[Ecky]

I'm not certain that a CEL breaks lean burn in the HCH1. It certainly doesn't in the G1 Insight.

When the battery goes, you're looking at ~$1000 for a rebuilt one which would probably be good for a minimum of 4-5 years, or if it turns out the CEL doesn't break lean burn, you can just remove it entirely and save the weight. HCH1 is a fantastic car, whose only real weakness was the HV battery.

In fact, you could remove the entire hybrid system and do something similar to what I did in my car, which is to just hook the 3 phase wires from the HV motor to a rectifier and drop the 70-300v DC produced down to 14v. Costs about $120 in parts (just 2 parts, in fact) and you'll have what is effectively a far more efficient alternator.

Even without lean burn, an HCH1 will probably beat an HX in economy. HCH1s with dead batteries are common and cheap as dirt.