Lately I've been seeing unexplained weird behaviors with my '05. For example it will not stay in ICE mode if I have the heater controls in the 'red zone' regardless of any conditions. It used to act right. My cabin heater pump is very erratic as to whether it will turn on when I go into EV mode. Sometimes it does and sometimes it doesn't, no rhyme or reason.

I was thinking of just disconnecting the 12 volt battery for a while (an hour?) to see if it might reboot things and clear up some of the weirdness.

Is there a reason I shouldn't disconnect the battery?

 

I and others have disconnected the 12V battery without any issue.

 

I have disconnected my 12v battery several times for short periods of time with no issues. However, I recently had some warranty work done on my '05 that required a couple days wait for the part. I also got them to replace my 12v battery under the battery warranty.

I am guessing that the battery was disconnected most of the time it sat in the shop waiting for the heater pump to arrive. When I picked it up, I didn't recognize the way it ran. High RPM's, no EV, 12-15 mpg, etc. This lasted about 100 miles and then it gradually returned to normal.

I am assuming that leaving the battery disconnected for more than a few minutes completely resets all learned behavior, whatever that may be. But, since that sounds like what you may want, go for it.

 

I seem to recall that the brake pedal travel has to be recalibrated if the 12vdc battery was disconnected. Some sequence of ignition key movements followed by several full depressions of the brake pedal. Might be something about that in the service manuals.

 

Anyone know anything about this? If I might need to do this, I would like to know what I'm getting into beforehand.

 

No. I installed all new speakers in my vehicle and hooked up some additional components to my Kenwood DNX7100 headunit that require a 12V battery disconnect. I did not have to do anything with the brake travel. You may lose some fuel map settings or other "learned" items but the vehicle will run as it did out of the factory.

 

I think this is what I recalled: https://www.greenhybrid.com/discuss/...ake-job-26610/

"I remembered that there was a brake calibration process that I had to do. With the car in park, you have to fully depress the brake pedal and turn the ignition on and then off. When I shifted into reverse from park, the brake light went out and the brakes worked fine."

I don't know under what circumstances this has to be performed, but seems to be involved with servicing the brakes.

 

I don't have a copy of the '05 FEH manual but here's what the 2008 FEH manual says about 12v battery disconnection:

"If the battery is disconnected, the Regenerative Braking System will need
to relearn the initial brake pedal position. After reconnecting the battery,
slowly depress and release the brake pedal one time.

Because your vehicle’s engine is electronically controlled by a computer,
some control conditions are maintained by power from the battery. When
the battery is disconnected or a new battery is installed, the engine must
relearn its idle and fuel trim strategy for optimum driveability and
performance.

To begin this process:
1. With the vehicle at a complete stop, set the parking brake.
2. Put the gearshift in P (Park), turn off all accessories and start the
engine.
3. Run the engine until it reaches normal operating temperature.
4. Allow the engine to idle for at least one minute.
5. Turn the A/C on and allow the engine to idle for at least one minute.
6. Drive the vehicle to complete the relearning process.
• The vehicle may need to be driven 10 miles (16 km) or more to
relearn the idle and fuel trim strategy.
• If you do not allow the engine to relearn its idle trim, the idle
quality of your vehicle may be adversely affected until the idle
trim is eventually relearned.

If the battery has been disconnected or a new battery has been installed,
the clock and the preset radio stations must be reset once the battery is
reconnected."

 

Everything seems to be working better since my battery disconnect a couple of days ago. I left it disconnected for about 1/2 hour. I cleaned the battery posts and ends while I had it apart. Since then it seems better. The only thing lost was having to reset all the radio presets, but that was expected. The cabin heater pump ran OK when it was supposed to this morning. The ICE would readily start back up when in EV mode and I turned the heater controls into the 'red zone" which it wouldn't do before.
Looks like my 're-boot' worked.

 

^^^ Makes me wonder if a periodic reboot might be good as preventative maintenance. My FEH is six years old this month and has never had the battery disconnected to my knowledge.