hv battery to battery shell = ground (negative)

[GIGEORGE]

I'm new to the ev world but ice mechanic for 32+ years. Trying to learn. Working on a 2013 model s with fatal battery codes. Battery appears to be ok based off of scanmytesla but has hv internal isolation failure codes. Battery is out and opened up, but before going any further i did a quick voltage test from the (forward) terminal at the pyro fuse (fuse removed) to the battery shell and get 170 volts. I'm assuming the case should not be electrically tied to the hv battery. I have a fluke 1508 on order, but seems to be more obvious than that. Thoughts? Am i wrong about my case voltage?

Thanks

 

[Lasttoy]

Call Re-Cell in San Antonio

 

[RedTesl]

Are you testing it properly? Shell should not have any voltage not at least in the 170 volts range

 

[GIGEORGE]

got my fluke insulation tester delivered (1503 instead of the 1507 but thats another story). testing from pyro fuse (rear terminal this time) to shell showed 9.9 megaohms. front terminal to shell >550. no signs of moisture anywhere in the pack. I started pulling modules and testing the voltage of each module as i removed and testing hv insulation test after each pack removed. each module had 23.8v. no change to hv test (9.9Mohms). took the 10 center packs out because they are the easiest. still the same results. tonite i skipped ahead and removed the rear cover (and all associated wires / connectors) and tested again. now >550 ohms. reinstalled rear cover and connected each wire / plug 1 at a time until i got the 9.9 result again. The connection that triggers the insulation leak is the purple eylet on the inner solenoid (but only when the 4 pin connector is plugged into the main bms). Interested in people smarter than me as to what the fault may be. Is it as simple as a fault with the main bms?

 

[GIGEORGE]

went a bit further. unplugged everything from the main bms except the 4 pin to the contactors (well actually an 8 pin with 4 pins empty). so with that plugged in and only the purple eylet on the inner contactor still has a short to the chassis. pulled main bms but haven't put it under the microscope yet. no obvious signs of damage.
if i swap in a used bms what needs done on the software / firmware side?

 

[GIGEORGE]

Ok, so i think im going about this the wrong way. My thought process somehow ignored the thought that the hvil would have to be connected to the shell at some point to make sure the shell was not shorted to the battery. I ordered a used bms to test (compare) the "short" i thought I had found. It turned out to be exactly the same, making me rethink my whole diagnostic process. I am still pushing forward blindly as I do not have any diagnostic information on what resistance values should be at various points (4) in the hvil loop (per the hvil diagnostic guide I just found from tesla), although there may be only 1 test point for the battery itself. Still looking for someone willing to share testing information on this.

 

[brainhouston]

As u already figured out, when the HV sense 4pin connected to BMS, u get 170v at the pyro, i was confused by that too
What are ur codes?
BMS has a special circuit for checking isolation, internal is when contractors are open, external when closed. This is why u have 4pin HV connector, it always sees HV battery.
Besides water, i can't really think of anything besides maybe pre-charge resistor is shorted to ground?... (unlikely)

I'm fixing the f123/w123 error rn, in my case it was obvious water intrusion...
If ur curious, see my thread here:

Car died. BMS errors f123, w123, w073, w035, w142, w158

Unfortunately my 2016 MX 90D decided to surprise me with these errors :confused: We had a few days of cold/snow days and the car did fine. Last couple of days its been above freezing and everything already melted. I drove the car in the morning, then parked on driveway. Few hours later, started...

teslamotorsclub.com

 

[GIGEORGE]

here's what I had for codes that I can remember:

BMS_u008
BMS_w172
BMS_w123
BMS_f123

 

[GIGEORGE]

only 1 small sign of water intrusion at the pyro fuse. 1/2 oz water in the bottom of the orange box and a little corrosion on the terminals. none seen in the case. but it does smell musty like it had more water in it at one point. no signs of anything on the middle 10 modules.

 

[brainhouston]

well, on 2013 the pyro is on top, right? so that most likely means water is inside the pack somewhere...
on my pack most of the water was hiding under emf bottom shields...
if u have a crack somewhere on the bottom, some water could have leaked out by now

f123/w123 is def internal isolation
i didn't have w172, but here's what i found for it:

BMS_w172_SW_Drive_Iso_Warning
The addition of a Limp Reaction to Repeated Isolation (f027) alert so the customers could feel a limp response a few drive cycles before the vehicle became Vehicle Off Road (VOR) was requested to allow customers to have ample warning and a noticeable driving symptom before the VOR occurs.

The current specification will set a limp when one of the following conditions are met:

• 2 drive cycles with alert 35 (SW_Isolation).
• 7 drive cycles with alert 142 (SW_Isolation_Degradatio).
• 2 drive cycles with alert 028 (SW_Drive_Iso_StdDev).

 

[GIGEORGE]

same lake different boat. lol i'm going to pull the last 4 packs this weekend and see if there is any sign of moisture, especially the front 2 packs. If everything looks ok, not sure how to proceed. replace old style fuse with newer pyro, change contactors to inconel, maybe swap shunt? i'm thinking of making extension harnesses for the lv connectors so I can test it without bolting it into the car.

 

[calimark]

Did you get anywhere with this?

same lake different boat. lol i'm going to pull the last 4 packs this weekend and see if there is any sign of moisture, especially the front 2 packs. If everything looks ok, not sure how to proceed. replace old style fuse with newer pyro, change contactors to inconel, maybe swap shunt? i'm thinking of making extension harnesses for the lv connectors so I can test it without bolting it into the car.