Powertrain failure alert, working 10 mins later

[nick]

The car would "start", then throw an error as soon as I tried to drive forward. It also threw an error when I attempted to charge.

List of errors reported:
269 BSM: Negative contactor/economizer stuck low
270 BSM: Negative contactor/economizer stuck high
939 DMC FW: Battery UnderVoltage fault
981 BMC FW: Bad Sta (only in summary list so truncated)
1067 DMCFW: Battery UnderVoltage warning
1085 DMC FW: PEM Vbat different from BSM Vbat warning

The diagnostics menu showed the battery voltage to be ~400V and the min/max brick voltages to be close and above 4V.

After about 10 minutes of fussing with it things started working again.

Also, about a month ago it threw an error complaining that the firmware version in one of the BMS modules didn't match the car-wide firmware. This resolved itself after a few minutes of opening/closing the charge port and attempting to start.

Wondering if it might be an intermittant communication problem between the car and the battery.

 

[petergrub]

Error 981 is DMC FW: Bad State Transition fault.

The missing negative contactor in the ESS would cause the undervoltage faults for battery voltage sensing circuits in the PEM, so you can ignore last four errors. Take a look at the negative contactor in the ESS and the wiring leading to it for issues.

The BMS modules? Did you mean BMB modules? The BSM—different from BMS—is responsible for most of the subsytems in the ESS, so you may want to look there too for issues that arise in the ESS.

 

[nick]

Sorry, typo, the firmware version error from a month back was a BMB module.

If it fails again with a BSM contactor fault I will take a look inside the PEM.

Thanks!

 

[petergrub]

If it fails again with a BSM contactor fault I will take a look inside the PEM.

Check inside the ESS. Remember, the PEM faults are a symptom of the BSM errors pertaining to the negative contactor.

 

[nick]

Check inside the ESS. Remember, the PEM faults are a symptom of the BSM errors pertaining to the negative contactor.

The negative contactor in the ESS? With you now, and ouch.

I have another ESS here I could pull a contactor from. Not jumping up and down with excitement over the prospect of pulling the ESS out of the car :-(

Error again today. Worked a few minutes later after a few retries.

 

[nick]

Can I swap ESSs or is the ESS keyed to the car in some way?

 

[nick]

Well, the contactor isn't intermittant anymore :-(

Lost all drivetrain power while driving back from lunch. AAA flatbed tow back to the office.

 

[petergrub]

I have another ESS here I could pull a contactor from.

I might have some. Used and a new. Let me check and get back to you before it gets any wors... and it's not driving. I'm on it.

Can I swap ESSs or is the ESS keyed to the car in some way?

I don't think the ESS is keyed, but you would possibly need to redeploy firmware if they have different versions. Replacing the negative contactor is probably the simplest route even though it requires dropping the battery to get to it.

 

[nick]

Guess I have a weekend job to do

I have the service manual with the steps for pulling the ESS from a 2.0... is the 1.5 close enough that the 2.0 instructions should be reasonable?

 

[ML Auto]

Guess I have a weekend job to do

I have the service manual with the steps for pulling the ESS from a 2.0... is the 1.5 close enough that the 2.0 instructions should be reasonable?

Yes. It is a little easier due to the Mil-spec connectors on the 1.5 vs the nut and bolt type in the 2.0.

 

[petergrub]

If this is your first time dropping a battery from a Roadster, then do so slowly and obviously with a second person to keep an eye on battery alignment, cables, and hoses. The latter tend to kink and bind, and last thing you want is more issues to resolve. Good luck!

 

[nick]

Doing the prep work...

1) Is there a "proper" way to shut down the car while keeping it in tow mode?
(one approach is to put it in tow mode, disconnect the cable to the transmission lock, then shutdown the car).

2) Is there are recommendation for a sealant to use for the battery cover/screw holes? It looks like it has a black liquid gasket type sealant.

 

[nick]

Answering the first one - you get get into the service menu from tow mode and shut the car down.

 

[ML Auto]

The original seals around the screws are a rubber washer. Silicone works better since the washers tend to crack, but you need to clean them up if you take them out again.

Be careful when you drop the ESS, as you need to support it in the rear up by the cooling hoses. It will not sit flat on its bottom without tipping over.

 

[petergrub]

Answering the first one - you get get into the service menu from tow mode and shut the car down

Yes, exactly.

Be careful when you drop the ESS, as you need to support it in the rear up by the cooling hoses. It will not sit flat on its bottom without tipping over.

I can't stress this ^ enough. Take MLAUTO's advice here. You can use steel angle and drilled holes to line up with the chassis support brackets on the back of the battery and long enough to rest on the lift table you use to drop the battery.

In my experience, the lift tables drop too quickly from the weight of the battery. Lift the chassis away from the battery as the two post lift moves slowly and fluidly. You will have more control over the removal of the battery and won't have the risk associated with ~1,000lbs suspended a few feet in the air by a wobbly, extended lift table.

Also, the washers around the outside of the battery as MLAUTO pointed out are self-sealing washers that use a thermoset plastisol. You can replace them with new washers or use silicone. To play it safe, get an electronics grade silicone or a silicone that doesn't evolve acetic acid—vinegar.

 

[nick]

Progress...

I installed a 2-post lift last month and spent the last week slowing working through the procedure to remove the ESS.

Got the cover off the ESS today.

It looks like the contactor ran a little hot... the nylon in both nylock nuts melted and dripped down.

 

[petergrub]

It looks like the contactor ran a little hot... the nylon in both nylock nuts melted and dripped down.

That shouldn't happen under normal circumstances. The only time I see that happen is if the nylock nuts weren't fully tighten down and the resulting contact resistance heats up the nut. Any other clues or observations?

 

[nick]

That shouldn't happen under normal circumstances. The only time I see that happen is if the nylock nuts weren't fully tighten down and the resulting contact resistance heats up the nut. Any other clues or observations?

Nuts didn't seem loose, though without the nylon they unwound easily once started.
Both nuts and surrounding areas looked to have the same damage (ie not obviously one side causing the problem).
The different metal bars and rings connecting to the studs all look tarnished from heat.

The small PCB mounted above the contactor looks to be a little golden - I will replace that as well.

I will double-check the crimping on the heavy cable - another possible point of resistance I guess.

Once I have the contactor out I will slice the top off and take a look there as well.

Dropbox - 2018-12-11 18.45.12.jpg

 

[ML Auto]

Damn Chinese contactors!!!

 

[nick]

I got the relay out.

The area around both studs is equally crispy.
No damage to the relay housing.

Thinking either A - poor contact to one of the studs resulting in heat which coupled through the relay path to the other stud, or B - poor crimp of the main power cable resulting in heat coupling through to the relay studs.

The main power cable crimp looks solid but hard to 100% rule out.