Thursday, March 21, 2013

Failure Analysis

The above image shows a failure of the highest degree when it comes to Hybrid Electric Vehicles. The dreaded P3009 (High Voltage Leak Detected) trouble code could be attributed to several problems. Battery modules leaking small amounts of electrolyte, problems within the air conditioning compressor and a few others come to mind. Burned out stator windings in a 2001-2003 Toyota Prius drive unit are a distinct possibility as the miles roll up. A Prius model year 2004 or newer uses a boost converter to increase voltage to MG2, which is the main drive motor within the transaxle. Higher voltage means that less amperage is needed to drive the wheels. Less amperage means less heat is generated within the motor, leading to longer life. Click on the picture for a closer view; you will see that the windings were hot enough to burn off the insulating coating that prevents the individual wires from conducting current amongst each other. This condition seems to be less common to Prius owners who have regular maintenance performed at the recommended intervals. The transmission fluid that Toyota recommends has been improved since the original Gen 1 Prius was released. The newer fluid is better at providing some insulating qualities that the earlier fluid lacked. Repairs for this condition involve either new stator assembly from Toyota (figure on spending around $2500.00 parts & labor) or replacing the entire transaxle with a used unit ($1500.00 parts and labor). There is no way to predict whether a used unit is "near failure" without partial disassembly, and warranties on used parts are often very short and may not include labor.

Tuesday, March 5, 2013

Let's Get Rolling!

The Small Shock project is underway with help in the form of a grant from the NMC Foundation. Actually, I should state that it has been underway for a number of weeks! The Spring 2013 Hybrid Electric vehicle class has been in session since January and we are well into our studies. An update to our project is long overdue. Our plans to re-purpose the Heathkit mini bike frame were dashed when it was obvious that the poor condition of the frame (rust from the inside and a major crack at an important structural point) would not provide the necessary strength needed to support the batteries. A trip to Actron Steel yielded a bundle of 1" X .095 wall tubing and the game was on. We are fabricating a new frame from the ground up. It is our good fortune to have a few experienced fabricators in our class! The main structure has been bent up and welded together. This paves the way for some improvements on our original design. The engineers at provided awesome support when it came to recommendations for our drive system. The new plan calls for 5 AGM style batteries. Our lab is now blessed with a Sevcon Gen 4 controller/inverter and Mars 19 horse power, 3 phase AC permanent magnet motor. 

Also in the mix is a DC-DC converter to drop the 60 volts down to 12 volts for the few accessories that are in the plans. Another feature will be the Cycle Analyst digital dashboard and battery monitor. This unit will calculate watts, amps and volts instantaneously as they are drawn from the battery. It will also allow us to check net values since the batteries were last charged as a sort of fuel gauge to determine remaining battery pack energy. Speed, distance and regenerative values will also be logged.

This first week of March should see our frame nearly complete with the motor brackets fabricated and installed. Once we have procured our batteries we can begin work on the framing in which the batteries will reside. Small Shock has generated a lot of interest in what goes on in the HEV lab here at NMC and has hopefully inspired some of our students to think about getting involved in the next generation of electric transportation.