On the driver side, there is a fuse panel with 3 connectors. One is always hot, one is hot when the headlights are on, and one is hot when the key is turned to ON. When I turn the key to on and press the engine start button, the voltage drops to only a few volts for a moment, and reset what I have plugged into that connector. I was wondering if anyone knew of a way to prevent that voltage drop from happening? Anyone know anything about tank circuits (using a capacitor to temporarially supply power while the voltage has dropped)?

 

It's one of several circuits that are dropped during engine cranking, like the radio and other electronics that might be bothered by a voltage spike from the starter. Honda assummed it would be safer to drop out your after-market accessory than to fry it with a voltage spike. At least it generates fewer service calls.

You might be better off finding another ignition source that does not drop when the engine cranks. Like the black/red wire on the IG2 relay. It's the same power source as the Option Connector you're using but it's ahead of the relay so it won't drop when you crank it. The IG2 relay is under the dash, to the right of the steering column, and kind of above the heater vent. There are 3 relays there, you want the one closest to the driver.

Bear in mind this wire (and the Option Connector too) are fused by a 50 amp fuse, and if you blow it you will lose lots of necessary gear, like AC and ABS. So you should always add an in-line fuse appropriately sized.

Chances are your accessory would require a really huge capacitor to supply enough power for even a few seconds. One of those half-farad stereo caps would supply a quarter amp for 4 seconds, assuming keeping the voltage at 10 volts or higher was acceptible.

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