How to bypass hchii high voltage battery

Discussion in 'Honda Hybrids' started by dev, Sep 27, 2012.

  1. dev

    dev New Member

    Hi All,

    I'm looking for a way to bypass the high voltage battery on my 2006 Honda Civic Hybrid. It seems that simply flipping the switch on the hybrid battery pack located in the backseat is not enough to bypass the hybrid battery and still be able to drive the car. I have reviewed the links that showed the procedure for bypassing the high voltage battery pack on 2003-2005 Honda Civic Hybrid, but the connector on the BCM (battery control module) is different for 2006 and up!

    Any suggestions on how to bypass the high voltage battery while keeping the DC-DC converter charging the 12v battery?

  2. Harold

    Harold Well-Known Member

    Will it not run with the pack dead? All you require is for the IMA to keep your 12v charged! This may not work when turning the pack off? H
  3. dev

    dev New Member

    Yes Harold. This is the question at hand. Is simply flipping switch behind the backseat enough to bypass the high voltage battery and more importantly does this keep the DC-DC converter recharging of the 12v battery while driving? :)
  4. msirach

    msirach Well-Known Member

    If you shut off the disconnect to the IMA battery, the 12v will not charge.
  5. lxmike

    lxmike Well-Known Member

    i ran my honda insight without a ima battery and as long and engine was running about 12-1300 it would charge the 12 V battery. Not sure if the civics are the same.
  6. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Would it not run (if it would run) like it's in a deep recal, all the time, ie: forget about making left turns in heavy oncoming traffic. And you'd have an Xmas tree's worth of trouble lights on.
  7. dev

    dev New Member

    I have gotten rather used to the gutless engine in bumper-to-bumper traffic. So why waste time and energy trying to charge the high voltage battery. The best answer I have gotten for keeping the DC-DC converter charging the 12v battery was this:

    The other suggestion I was emailed was to pull the 10A fuse under the hood after disconnecting the 12v battery and then re-connect the battery again.

    Last edited: Sep 28, 2012
  8. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    As far as I know all communication between hybrid components in the HCH-II is over a CAN bus (hence the ability of a firmware flash to completely change the behavior). This means that there is no simple wire manipulation which will let you control the functionality (such as enabling the DC-DC). I'm sure this isn't the answer you were hoping for but I don't think you are going to be able to accomplish your goal without extensive programming expertise and possibly some spoofing hardware of some sort.
  9. dev

    dev New Member

    Hi All,

    I went to the garage last night, opened the hood disconnected the 12v battery then pulled out a 10A fuse from a super small fuse box tucked between the radiator and battery. According to the manual it is called IMA1 fuse. Connected the 12v battery and started the car!

    When pulled out the drive way I noticed ultra smooth progressive acceleration (no more bucking). When I floored the gas pedal the car just creeps forward slowly and then starts to really take off (which is about how the car used to responded before pulling the fuse). A red battery light was ON also. The IMA light which has always been ON so I am use to that one. One light I didn't expect to be ON was a green light "flashing" next to the "D" indicator. This light doesn't go away or stop flashing, even when parked.

    The way I verifed if the 12v battery is getting charged or not was by turning on the high beams and the A/C full blast. Then slowly rev'd the motor past 1500 rpms and notice the headlights would get slightly brighter and when I rev'd over 3500 rpms the headlights got slightly dimmer. I repeated a few times and could tell that something was feeding the battery additional juice while rev'ing the motor.

    Today I drove to work and back like this. Absolutely no issues! I'm so use to flooring the gas pedal that now I have to pay attention to the cars behind me. My car now accelerates a little slower than before from a stand still (which is not a problem for ME). I'll continue to do some tinkering around with the IMA fuses under the hood but from what I can tell the DC-DC converter is still working and charging the battery only when rev'd above 1500 rpms (which where the motor seems to be at in normal driving).

    But if your idling or stuck in extremely heavy traffic for an extended period of time, along with the A/C at full blast or headlights ON you'll probably need to shift from "D" into "S" or even "L" to keep the rpms close to 1500 so the DC-DC converter can capture energy from the IMA generator. Or you could just turn the car off until your moving again.

    Not sure exactly what IMA1, IMA2 and Booster MS mean in the manual? And what functions they specifically controlling when the fuse is plugged or unplugged?
    Last edited: Sep 29, 2012
  10. Harold

    Harold Well-Known Member

    Check your 12V battery with a multi meter that has 12 v position on it and check when ICE is off and when the ICE is idling and so on. If it is charging it will show 13.7 v or even more.This way you will know you 12v is being taken car of. Also if you have a scan gauge you can set one of the windows to show voltage. H
    Last edited: Sep 30, 2012
  11. lxmike

    lxmike Well-Known Member

    I'm with Harold on this one. connect a volt meter to your 12V battery and check volts with engine off, should read 12-12.5, then start engine and should be about the same. then rev engine above 1500 rpm's and if it is showing 13.5-14.2 your getting your 12v battery charged. also turn on headlights and ac and radio and see what readings you get.
  12. cswee1932

    cswee1932 Well-Known Member

    Any more info on this test? Sounds pretty interesting....also what is the MPG like now with the battery taken out of the equation...

    Sounds interesting,

  13. Harold

    Harold Well-Known Member

    I am not sure that little 12v is going to handle everything. TheA/C in this car is electric . The steering is electric. I would definitely turn the A/C off. Hope all is working well . Please fill us in. H
  14. jmelson

    jmelson Well-Known Member

    The electric AC runs off the 150 V bus. There is also a belt-drive AC
    compressor in the same unit. I think the electric power steering runs
    off the 12 V, though. But, even if the battery is out, the 150 V bus
    charges the 12 V battery (and supplies the 12 V loads) with a DC-DC

  15. Harold

    Harold Well-Known Member

    Is there a belt drive for the A/C on the HCH 11? I cannot see that. H

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