This discussion might shed some light on why my headlights dim a bit when the IMA is called on. I have installed an aftermarket lighting control system which includes its' own relays for headlights and taillights, bypassing the stock relays. The unit automatically turns the lights on when it's dark. I elected to include the Daytime Running Lights feature, which has the headlights only on at all times. Rather than tap into the cars harness or fuse panel for the relay switched power, I connected directly to the battery (+) terminal.

Even so, I get this dimming of the headlights when the IMA kicks in. It's not a lot, but just enough to be annoying. Perhaps this is an indication that the 144v pack is isolated from the 12v system when IMA is working, leaving the native power of the 12v battery to handle some portion of the cars' electrical needs (and my DRL connection) on its own until the IMA is idle and the 144v battery can be spared from its main job.

This leads me to wonder if, with my DRL drawing directly on the resources of the 12v battery, it wouldn't be prudent to replace the tiny stock 12v battery with the full sized 12v battery the non-hybrid civic uses.

Alternately, perhaps I should track down the wire(s) which normally power the headlights (with the help of the Electrical Service Manual that I picked up recently) and tap in to those instead of going directly to the battery. I'm pretty sure I never had headlights dimming due to IMA use on the stock setup, so perhaps they are powered upstream from the circuit that tends the SOC of the 12v battery. I am a little more cautious about going this route without some council from more someone who understands the HCH electrical system better than I do. My understanding of electronics is pretty basic, and the HCH electrical system is relatively complicated. I wouldn't want to freak out the cars electrical monitoring system with a significant current draw in an unexpected time and place.

Any suggestions would be greatly appreciated.