BillPitman
Well-Known Member
- First Name
- Bill
- Joined
- May 10, 2021
- Threads
- 22
- Messages
- 388
- Reaction score
- 211
- Location
- Pa.
- Vehicles
- Ford Escape, ‘21 J2 Mach e, 2024 Maverick Hybrid
- Occupation
- Retired
Lee, please do check your 2 parameters, I have wondered why the contactor voltage was reading higher than system voltage… BillVoltage drop is proportional to resistance, so a higher voltage drop is bad. However the positive contactor voltage should always be less than the pack voltage, and the negative contactor voltage should rise above 0V. I’ll have to look at that on my car. Might be rounding errors or something. A good contactor in spec should always have a voltage drop less than 0.5V, 1.0V would be double spec and where I would get concerned.
The entire battery circuit is isolated from the chassis. The leakage resistance is the resistance between the battery circuit and the chassis. Normally it should be very high because nothing should be touching the chassis or it’s insulated. If there is a problem in the system somewhere such as a HV cable rubbing through, cell tabs touching ground, or moisture in the pack the resistance will go down, and the BECM will shut down the pack.
Todd had an isolation fault at the end and I theorize it may be because a contactor coil touched the contact plunger while energized. Coil insulation melting through could cause that.
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