Hybrid vehicles have been on our roads since the model year 2000 and are now developing problems just as non-hybrid vehicles do. In this article, we will cover a couple of hybrid vehicles that we've diagnosed and repaired. Let’s start with the first hybrid vehicle that hit U.S. roads, the Honda Insight. The Honda Insight is not a real common vehicle, but its hybrid system was the foundation that is still used today on the 2018 Acura NSX.
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The problem Insight
This 2001 Honda Insight (Figure 1) came in with a code "78" Honda DTC (Figure 2) that translates to a P1449 (High Voltage (HV) Battery Deterioration). This common code is related to Honda’s weak link in the IMA system — the HV battery. The HV battery used on this vehicle is a Nickle Metal Hydride cylindrical cell that has had issues maintaining a balanced charge. Since our problem vehicle is an Insight that only has a 3-cylinder ICE, it is important that the HV battery does its job in supplying power to the overall powertrain output.
The owner of the problem Insight normally does not start or drive the vehicle for over a month. She arrived at our shop complaining of a loss of power and the check engine light illuminated. We performed a visual inspection after speaking to the Insight owner and found a gym bag behind the right front seat. Normally, no big deal, but on a Honda Insight Gen 1 this is where the HV battery vent is located and the bag was blocking air flow to the HV battery. We showed the Insight owner where the vent was located and asked her not to place her gym bag behind the passenger seat anymore. I explained that blocking the vent was causing the problem with the HV battery. I told her that the HV battery needed to be cooled or it would be damaged.
Next, I opened the Insight’s hood and proceeded to show her the HV battery label (Figure 3) that states the 144 volt HV battery can become damaged if the vehicle is not driven at least 30 minutes a month. Since the Insight owner purchased this vehicle used about 3 years ago she did not receive any information on how the vehicle operated. She, like many of our customers, thought that you just get in and drive the vehicle like any other.
After performing a diagnosis, we uncovered an out of balance HV battery so we tried the easiest fix first and performed the MCM (Motor Control Module) Reset. This reset requires starting the engine and holding the RPM at 3500 with no load (in neutral) until the IMA Battery Level Indicator (BAT) on the gauge displays a normal level. Since this HV battery was so far out of balance, we performed three MCM resets only to find that there was little to no improvement. The next step was to recommend and perform a HV battery reconditioning.
The process of reconditioning an HV battery begins with removal from the vehicle and cleaning all the vents in the HV battery case. Then we connect the HV battery to our reconditioning machine and set it up for discharge and charge cycles. The HV battery sticks are connected to the NuVant EVc-30 (Figure 4) in parallel. This type of connection ensures that each battery stick (which contains 6 D-size cells) can accurately be discharged, charged and finished to the correct battery level. The NuVant EVc-30 HV battery unit is operated by a PC that graphs and compares all the different sticks, so the user can see if any stick needs to be replaced.