Disassembled battery casing and wanted to check outputs of each bright copper connections, two big orange cables. Assuming about 64V on one and the remainder on the other, 143 Volts. ( gen II ) There must be another common point in the HV Battery area, Is there? I'm assuming up front, the MG units. but running a neg line from the front of the car to the hatch area, even well insulated and a larger guage does not appeal to my living instincts.
Hi Andy, If you wish to measure the voltage across the traction battery, you would install the orange interlock switch, then measure the battery voltage at the system main relays. You'll probably measure 220V or thereabouts (201.6V nominal). There is no common point from the traction battery leading anywhere since the high voltage is isolated from the body. The two MGs use three-phase AC so they certainly will not be connected to the battery. Your message above seems to imply that the traction battery produces a 64V output and a 143V output. This is incorrect. The battery produces 200+ volts. The traction battery interlock switch is not located at the midpoint of the battery, as had been the case with Classic.
Hi Pat, ty. The first 1/3 of battery modules read something less than 64 Volts, in increments of something less than 8,16,24,32,40,48,56 and then 64 volts. I then contnued measuring after some sort of break in the pack assuming a wiring change ( series/parallel) That total segment from the first neg in the latter 2/3rds read again something less than 143 Volts, I made the nice person-umption that the voltage was devided as such to the two copper terminals. Obviously that was incorrect. For convenience I was only measuring from the rear of the modules. I also measured a few modules on both sides, but considered this too cumbersom and subject to an accidental short. I don't really consider my measurement system as too accurate and believe that internal and cumulative resistances affect accurate readings. I was not about to disassemble any modules as my car works. Back to the subject: where can I find this relay to measure the HV, in fuse box area? is relay marked HV? What should I watch out for as far as shorting it out? Thanks much for your reply. Andy PS: You are right, I forgot the MG's are AC
Hi Andy, Pls see my comments below: The break in the pack is just where the orange traction battery interlock switch is located. If you install that switch, then there will no longer be an electrical break. All 28 modules are wired in series. There are three system main relays, installed within the traction battery case. You would have to examine the wiring to find where the negative lead from the battery module at one end connects to one relay. Then find where the positive lead from the battery module at the other end connects to another relay. The third relay bypasses a series resistor which limits current in-rush as the electrolytic capacitors in the inverter are charging up upon power-up. If you measure voltage from the traction battery negative lead to the positive lead then you should obtain total voltage of 200+ V. Since the traction battery is not under load when you are measuring voltages, module internal resistance should not impact the accuracy of your measurements. The internal resistance would start to be an issue only if you are measuring voltages while the battery is flowing an appreciable amount of current.
Did you take the whole cover off, or just the end over the relays and ECU? I've recently put up a fairly large rundown on doing the former and some testing, and looking at that will show you how the "split" is wired to the safety plug. Pretty simple, really. . _H*
Hello H* and Pat, Thanks much for your posts. Everything is totally clear now. Hobbit, your rundown is incredibly good, good info to reread and digest. To answer your question, I basically did the same thing you did as I was curious to see how everything worked and measured. I was not aware that the break at the 1/3 point was the HV switch interconnect, so my measurements were not quite kosher. I did not touch the ECU.
In reassy of the left rear seat ( 2 large bolts ), the inner bolt was extremely tight, maybe a burr on the female side. I finally used some more force and got it. Never identified the problem tho.
