I have a 2003 honda civic hybrid. The IMA battery is a little old so I use a grid charger occasionally to extend it's life. after charging a couple of days ago, when I started the car, the IMA light stayed on. also the red battery indicator was lit. neither the charge or assist worked at all. And the IMA battery indicator rather quickly dropped to zero. While still running, I popped the hood and removed the positive battery cable. The engine immediately shut off. On a normal car this is generally an indication the alternator has stopped working. I read there is not a conventional alternator on the hybrid. What would I need to replace on a hybrid to fix it when this happens? Please help me as I cannot afford to buy a bunch of parts trying to hit or miss the problem. All things worked correctly before this happened (charge, assist, auto stop). no trouble lights or issues. Thanks in advance for any help

 

If you disconnect the 12V from any "normal" car, it will stop running.


No. The Honda IMA Hybrids do not have an alternator. They use the IMA motor, the HV battery and the DC-DC converter to provide 12V power/charging.


No. All things were not working correctly as you were grid charging. I presume this was necessary to prevent an IMA light or recalibrations.


The first step is to reconnect your 12V. Rev and hold the car at 2000 rpm for 30 seconds. See if the 12V light goes out. If it comes back on at idle, your HV battery has deteriorated to the point that the DC-DC converter won't operate outside the "sweet spot" where engine rpm produces the desired voltage/current from the IMA motor.


You should also load test your 12V battery to insure it is good. Checking voltage doesn't work. Saying your lights and everything works doesn't work. LOAD test it.


There are at least a couple grounding straps between the engine/tranny and the body. Confirm these and the 12V (-) cable are in good condition.


Good luck,


Steve

 

thank you for your response, Steve. While I am sure you are much wiser than me concerning hybrids, and I will try your advice in the morning light. You are incorrect about "normal" cars. A non-hybrid car, once started, will run off of the alternator. The battery is used for starting. alternator for running. If you really doubt this I will take and download a video of my chevy van running with the battery disconnected. This is a common test many mechanics use to determine if the alternator is putting out enough current to run the vehicle.
I have tried your test with the idling at 2000+ RPM's. the battery light never goes off. I have tested the battery under load with an appropriate battery tester with a load switch. It drops but stays in the green. tomorrow morning I will check the 12v grounding cables. Thanks again for the tips! have a great day!

 

I would not use a mechanic who employs that test. The battery keeps the voltage in a narrow range and tamps down any spikes. He may confirm that the alternator is working adequately - at the cost of blowing up some of the car's electronics, worst case, taking out the ECU. That test may have been reasonable in 1927, when only the ignition system and the lights were wired in, but in 2017, it is a horrible idea.