Limp Lexus...
AECS Equipment tech support team recently assisted a trouble case where this Lexus Hybrid had no EV mode, only the internal combustion engine.
Hybrid and EV vehicles are around our roads in reasonable numbers so do not let the opportunity get away from your repair business to electrify your bottom line.
Expect hybrid vehicles in particular to increase in popularity while they remain exempt from road user charges.
Problem presented to the support team
Lexus CT200h 2012
No EV mode on the vehicle, only power from the vehicle's combustion engine. The workshop had carried out a diagnostic scan of the vehicles systems. The following report below was shared with the AECS support team. What to do next was the question?
It should be noted that to work on any vehicle, training and understanding of the systems is required before undertaking any type of repair. This is particularly true with EV vehicles due to the high voltages involved. It is too dangerous to attempt a repair without being qualified in electric vehicle repair. The workshop who were involved in this repair had a qualified technician who was carrying out this job. In this case the technician would be working with a live battery with over 200 volts to carry out the repair. In the NZ electric vehicle repair industry, anything over 55 volts is considered high voltage and requires appropriate training.
Coming into direct physical contact with anything over 55 volts can be fatal.
In the Launch Auscan 4 shared diagnostic scan we can see potential issues with the battery pack sensor module. But it could also mean we have cells that are out of voltage range or potential connection issues in our cell monitoring wiring.
Next steps…
AECS Equipment support recommended looking at the live data for the cell voltages and also the internal resistances for all of the cells. This will give an indication of what maybe going on inside the battery pack.
In the Launch live data report below we can very quickly see some issues.
Cell V02 = 0 V
Cell V03 = 24.989 V
Most cells seem to be a fairly normal 15.7v to 15.8v range. The internal resistance readings of all the cells were identical so I doubt we have an actual cell issue but more then likely an issue with either the battery pack voltage sensor wiring such as a break in cell V02 wiring, shorting between V02 & V03 wiring, the control unit itself or both.
This battery pack contains 14 cells. A cell contains two blade type nickel-metal-hydride batteries(NiMH). These are all joined together in a series circuit by small copper connectors called bus bars on either side of the battery blade cell.
We would now need to remove the battery and open it up to inspect the cells, wiring, bus bar connectors
The customer was called and gave the green light to carry on with our diagnosis of their battery issue. The vehicle was put through a power down procedure, the HV cables to the inverter from the battery were removed after measuring that they were 0 volts using a category 3, 1000 volt high voltage multimeter. This was to ensure the main battery contactors were in fact open. A critical safety step. Do not assume with high voltage.
High voltage class 0, 1000 volt category 3 insulated gloves were now worn by the technician as the battery is live inside with over 200 volts, also category 3, 1000 volt insulated tools were used for the procedure.
The top of the battery pack was removed and the plastic bus bar battery connector covers were removed. The following picture was shared.
We can see corrosion all over the bus bars, also the voltage sensing wiring connectors.
This is a common problem. The battery cells can give off corrosive gas under load, this corrodes the bus bars, these then heat up more than otherwise under load and heat up the cells. A chain reaction that makes the problem worse.
All bus bars now need removal, cleaning in a solution of salt and vinegar, then polishing to a mirror finish with p2000 wet & dry sand paper to restore conductivity.
After carrying out the bus bar repairs, the voltage sensing wires were checked for continuity and shorts. None were found, so it was likely the battery voltage sensing control unit was faulty. This could be rechecked after battery assembly and refitment to the vehicle.
After refitting the cleaned battery to vehicle, the voltages shown in the battery voltage controller were still indicating issues with cells V02 & V03. We now knew for certain that our control unit also had an issue.
A used controller was bought and fitted to the battery pack. Fault codes cleared and now working perfectly in EV mode.
Battery voltage control unit. This is fitted inside the battery pack, between the end of the battery cells and the main contactor assembly.
Launch scan tool live data of cell voltages with the replacement battery control unit installed. Now displaying a battery in good condition. Minimal cell voltage variations.
Technical support can make a huge difference to your outcomes in many situations. Quality equipment and support with driving makes returns more certain. AECS Equipment has considerable experience in the vehicle repair industry and supports the equipment we supply. We regularly upskill ourselves to be ready to assist our clients.
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