Do you Really Need Your Hybrid Vehicle’s Battery Replaced?

Have you had a qualified technician check the battery for your hybrid vehicle (High Voltage Battery or HV battery) to see why it is not performing?  Some technicians will just tell you a code saying battery deterioration (P0A7F for Honda or P0A80 for Toyota) and that it needs to be replaced. These codes are only […]

Have you had a qualified technician check the battery for your hybrid vehicle (High Voltage Battery or HV battery) to see why it is not performing?  Some technicians will just tell you a code saying battery deterioration (P0A7F for Honda or P0A80 for Toyota) and that it needs to be replaced.

These codes are only telling the technician that the Electronic Control Module (ECM) is receiving data that there is a variance in block voltages that exceeds a set value and you are just seeing the indicator in your vehicle (IMA light for Honda the red triangle of death for Toyota)

There is more to it than that though.  There are 4 possible reasons for the variances in the block:

  1. Over heating of the HV battery,
  2. crystals built up in cells of a module(s),
  3. corrosion of connectors or
  4. battery that is just used up.

Knowing how an HV battery works can help you know if your battery really needs to be replaced.  HV batteries are made up of modules.  Modules are made up of cells (usually 6 or 7 1.2 volt cells).  The cells are connected in a series to produce in the case of a 6-cell module a 7.2-volt module or 7-cell makes an 8.4-volt module.  Then those modules are connected in serious to make up the HV battery pack.

Overheating of the HV Battery

With a 2010 Prius that has 28 modules with 14 monitored blocks (2 modules per block) to produce 201.6-volt HV battery. So, an HV battery starts out like much like a household flashlight with three D-cell batteries using a 3.6-volt light bulb. The household flash light is just much smaller. With all the voltage running through all the cells, one overheated or bad connection due to corrosion or degraded cell can cause a problem.  One bad apple (cell) does ruin the whole barrel (HV battery).

We had vehicles come in warning light on that indicated HV battery replacement with wiring problems causing HV battery cooling fan not to work, over heating caused by pet hair and debris blocking cooling passages of HV battery. To correct overheating, we repair the wiring, clean the HV battery cooling passages.  Clearing codes test driving to find a happy HV battery preforming as it should.

Crystals Built Up in Cells of a Module

Batteries store and release energy by chemical reactions. Sometimes crystals can build up in cells causing them not to be able to store as much energy. It’s like having a gas can with rocks in it. The gas can cannot hold much gas/energy. Removing the rock restores the amount of gas/energy it can hold. In Nickel-Metal Hydride batteries the crystals that build up can be revised by cycling HV battery with special equipment, cycling the cells with slow charging and deep discharging.  Auto Alternative Service & Sales uses the ProLong System to charge/discharge/test HV batteries.  AASS installs a special harness to perform the service to a HV battery restoring it back to operation. Prolong harness and service can be done as a maintenance to prevent crystals from building up also. 

Corrosion of Connectors

Normal household battery-operated devices and 12V car battery corrosion can ruin or cause them to work improperly. Corrosion can affect a HV batteries performance, also. Cleaning and correcting corrosion connection problems can get HV batteries back into operation of storing energy and providing energy when needed.  

Battery that is Just Used Up

When the HV battery has modules that are no longer capable of storing or releasing energy, we can test, grade, and match it to other modules to make a HV battery pack that will perform as designed for many years. After you have a HV battery with matched modules, you bring your hybrid in for maintenance every 6 months to a year to keep the buildup of crystals from returning to an unacceptable amount, your HV battery will perform as designed for many many years. You will have to have a Prolong Charging Harness installed to perform this service.

So, do you really need a complete HV battery replacement? Or just some repairs at a much less expense? 

Here at Auto Alternative we have national recognized Automotive Service Excellence Certified Master Technician L1 and Hybrid Certified to care for your vehicle. We can diagnose, and repair needed components to get your hybrid vehicle back on the road.

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