Running the HCH1 without IMA Battery!

[micksam7]

Hey all, first post, long time lurker.

I've discovered how to get the civic's 12v battery to charge without an IMA battery installed/connected.

Disclaimer: You could fry your MDM, ECU, DC->DC converter, or worse if you do this. The car will not behave correctly. And you cannot leave the car idling, as it will drain the 12v battery! Also, don't blame me if something fouls up.

It's fairly simple, and very similar to the insight:

1. Remove connector #1 from the MDM [on the bottom, 1st from the left, -NOT- the black connector!]
2. Leave the IMA battery connected, with the switch off, or connect the DC->DC converter manually to the IMA battery lines.

The DC->DC input lines are the smaller orange wires connected to the bottom left of the IMA battery, carefully pull back some of the orange insulation to check polarity on the DC-DC lines [the inner lines should be black and red/orangeish].

If you leave the IMA battery in, disconnect all other cables [on the top, and the temp sensor clip going to the top of the MDM], -except- for the main voltage lines, and the DC->DC voltage lines [the bottom left orange clip].

After that, you should be able to start the car, rev the engine above 1,500 rpm, and the 12v battery should get a charge.

Disadvantages:
- The car will take a moment to start, I assume because it tries IMA starting first, and we've disconnected a line telling the ECU the battery isn't present.
- The car will not charge below 1,300 RPM. The IMA voltage is too low [~60 volts] It will only charge when not idling! [>90 volts it seems]
- Like the insight, the car will temporarily shut off the DC->DC converter after about 4,000 RPM. It will not come back on for 10 seconds or so after.

I've run my car in a short loop this way, but have no intention on leaving it like this. I have no idea the long-term damage this could pose and have no intention on finding out.

[Hybrid-Battery-Repair]

We've been lending out bypass kits to Civic repair customers for several months now and probably have a dozen cars running with them right now.

Also, in some instances, AC will not work.

One of the pieces of the kit is a junction board off a Civic Hybrid for the customer to install in place of their battery - far safer.

[JohnVirginia]

Would removing the 100 amp fuse on the junction board (and leaving everything connected and main battery switch on) accomplish the same as these mods (micksam7's solution) or act the same as the bypass kit? I ask this because when I had a blown 100 amp fuse, the car acted just as described with of course the addition of no IMA battery charging or assist. That is, 12 V light on below 1300 rpms and no AC.

There does not seem to be a straight forward way to keep the idle speed above 1300 rpms except to keep your foot on the pedal or adjust the mechanical linkage buried down on the driver's side of the engine.