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BSM: V_ess too low during precharge

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After doing a lot of very slow charging to recover my battery pack, I now get the BSM: V_ess too low during precharge error. It happens when trying to charge and when trying to drive. The battery is good, lowest brick is 3.97V highest is 4.00V. Pack voltage is 395V. But in the service screen the PEM has only 254V. That sounds like a problem! I'm thinking a resistance between the ESS and PEM?
 
It looks like v_ess is the battery voltage after the contactors, and v_bat is at the battery. So there is either a resistance in the line to the pem, or a short somewhere after the contactors. I'm suspecting the insulators on the pem igbt's, but could be a shorted capacitor too.
I'm getting the new 3.0 battery, so the pem will be updated anyway, but that means no car until then. It also means towing the car to the other side of the island, and probably shipping it to Honolulu on a barge. Very expensive! Since it won't drive, It would have to go in a container, even more $$$.
I'll probably fix the pem, even though it will get changed out later. grrrrrr
 
But in the service screen the PEM has only 254V.

It's normal. The voltage stays there until the HV contactors close and then PEM sees full battery voltage. So, the reason your PEM doesn't see full battery is that the precharge test failed. The precharge circuit is used to determine if the high voltage circuit is safe to apply high voltage.

I'm suspecting the insulators on the pem igbt's

The IGBTs shorting would cause a desaturation fault. The capacitors on the other hand could possibly be part of that precharge issue. If you find nothing awry there, then definitely check the precharge circuit in the PEM. Perhaps thefortunes could share his experience with the precharge circuit error and subsequent fix.

I think you need to get the PEM issue resolved before you go into Tesla to get your 3.0 pack. I heard Tesla doesn't replace the PEM, but replaces a board in the PEM. Check with your service center ahead of time and let us know what they say. If you need to repair the PEM ahead of time, then we should get going on that ASAP.

Preserve your battery in the meantime by properly shutting down the Roadster and removing the service disconnect plug on the battery.
 
It's normal. The voltage stays there until the HV contactors close and then PEM sees full battery voltage. So, the reason your PEM doesn't see full battery is that the precharge test failed. The precharge circuit is used to determine if the high voltage circuit is safe to apply high voltage.

Not normal. The precharge circuit is a relay and resistor that goes around the negative contactor. It's purpose is to slowly charge the large capacitors in the PEM. This avoids damage from high inrush currents. The precharge relay closes, and the V_ESS voltage ramps up as the capacitors are charged. When V_ESS is very close to V_BAT the negative contacor closes and the precharge relay opens.

Since V_ESS didn't make it up to near V_BAT in the allotted time, the error was thrown and the relay opened.

The IGBTs shorting would cause a desaturation fault. The capacitors on the other hand could possibly be part of that precharge issue. If you find nothing awry there, then definitely check the precharge circuit in the PEM. Perhaps thefortunes could share his experience with the precharge circuit error and subsequent fix.

The precharge circuit is in the ESS. I plan on inspecting everything in the PEM and replacing caps and insulators since they have been going bad on others. If the problem persists, I'll be stuck with shipping it to the SC for the 3.0 battery.
 
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Since V_ESS didn't make it up to near V_BAT in the allotted time, the error was thrown and the relay opened.
You're on the right train of thought. Check the resistance values of the precharge RC circuit. Since it's an RC circuit, either the resistance of the resistors, or the resistance of the capacitors is throwing off the precharge time assuming the voltage source is functioning properly.

In thefortunes case, he found a blown IGBT on the CIC/IO board in the PEM.
 
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Sorry, I have been way too busy at the office (and a vaction thrown in there too) and have been neglecting my duties on this forum :)

Yes, when I got that error (after replacing the insulation due to a desat fault), I found a capacitor blown as well as the IGBT on the CIC I/O board blown. That IGBT is the one surrounded by the heat sink on the board.

If you are still having issues shoot me a PM and I may be able to help. The CIC I/O is kind of a pain to get out, if I recall correctly.
 
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Sorry, I have been way too busy at the office (and a vaction thrown in there too) and have been neglecting my duties on this forum :)

Yes, when I got that error (after replacing the insulation due to a desat fault), I found a capacitor blown as well as the IGBT on the CIC I/O board blown. That IGBT is the one surrounded by the heat sink on the board.

If you are still having issues shoot me a PM and I may be able to help. The CIC I/O is kind of a pain to get out, if I recall correctly.

Do you have a schematic or other info on the PEM? It would help.
The other possibility is the HVAC unit. It uses a 400V compressor, so a short in that unit can also give the error.
Since I don't have a way to fake the HVAC, I still plan on servicing the PEM, especially with many having problems with it. If that doesn't fix it, it's on to the HVAC.
It will be a while. I am in Oregon for a few months and the car is in Hawaii with the plug pulled on the battery.

Can anyone confirm that the existing PEM is kept with the new battery install? I've heard yes and no.
 
Can anyone confirm that the existing PEM is kept with the new battery install? I've heard yes and no.
All the owners I have talked to say the service centers let them keep their PEM and only replace a PCB in the PEM before upgrading the firmware for the 3.0 battery upgrade. On the chance of coincidence, a factor that may be playing into the PEM replacement rather than replacing a PCB board in the PEM may have something to do with whether the PEM is universal or not. Check here if you want to see which PEM you have.

I still do not have a definitive answer on which board they replace, or when they determine a PEM needs to replaced for the 3.0 battery upgrade. Please let us know if you can get a clear answer.
 
All the owners I have talked to say the service centers let them keep their PEM and only replace a PCB in the PEM before upgrading the firmware for the 3.0 battery upgrade. On the chance of coincidence, a factor that may be playing into the PEM replacement rather than replacing a PCB board in the PEM may have something to do with whether the PEM is universal or not. Check here if you want to see which PEM you have.

I still do not have a definitive answer on which board they replace, or when they determine a PEM needs to replaced for the 3.0 battery upgrade. Please let us know if you can get a clear answer.


13th April 2018
Hong Kong

Morning Richard,

For 3.0 Battery upgrade, the PEM unit will not replace, but a Power Electronics Controller (PEC) board will be replaced which is inside the PEM unit. A newest firmware will perform update once all hardware install back to the vehicle.

After 3.0 Battery upgrade, we will provide 3 years / 36000 miles (~ 57936 km) warranty with the new battery unit.


Thanks

xxxxx xxxx | Lead Service Advisor – Hong Kong
Tesla Motors HK Limited
 
For 3.0 Battery upgrade, the PEM unit will not replace, but a Power Electronics Controller (PEC) board will be replaced

Interesting choice on Tesla's part. The PEC board is the brains of the PEM and contains the DMC (Digital Motor Controller), PM (Pedal Monitor), and DFC (Dual Fan Controller) firmware on three separate processors. All of the latter processor's firmware can be, and is usually , upgraded via the CAN bus.

Then why replace the PEC board to upgrade the firmware? Perhaps there are hard-coded lookup tables on the PEC board that need to be readjusted to compensate for the new aerodynamics, battery weight, and rolling resistance to allow the Roadster to achieve 300-400 miles range.
 
I'm finally back to working on the Roadster. I have the insulation, and I've replaced the caps on the first board of the three. I noticed that there is some kind of coating that was applied to the board at the factory after it was soldered. It is clear and is probably to prevent corrosion in the harsh environment as well as to provide extra insulation in this high voltage area.
I want to recoat the areas I've worked on, but I don't know what they used. I do know that it is soluble with the alcohol I used to clean up the flux.
Anyone have any ideas?
 
It happens when trying to charge and when trying to drive. The battery is good, lowest brick is 3.97V highest is 4.00V. Pack voltage is 395V. But in the service screen the PEM has only 254V.

These are the exact same symptoms I had when pulling a fault #981earlier this summer. It was the PEM, waiting for final diagnostics on the old PEM to see specifically what the issue was.
 
You're on the right train of thought. Check the resistance values of the precharge RC circuit. Since it's an RC circuit, either the resistance of the resistors, or the resistance of the capacitors is throwing off the precharge time assuming the voltage source is functioning properly.

In thefortunes case, he found a blown IGBT on the CIC/IO board in the PEM.
Am i right in saying the recharge RC circuit relies upon the resistor inside the 400V controller? looking at the controller the large metal film resistor inside appears to be part of the circuit the car needs to decide to start or not. ie, if this resistor fails then the error triggers and it doesn't power on or charge. Is this correct or have i misread the board?
 

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I have thoroughly investigated the fault i have had within the 400V controller resulting in Error 276 and ive found the following failed components inside.

1) Mosfet TR3 IXUS IXFL100N50P failed RS Components
2) Resistor R3 Cracked 68 OHM ordered Farnell
3) IC1 MCP6031E Shorting to ground between pins 3-6 and pin 4 Farnell
4) Blown LED Kingbright L-934LID 3mm Red.
5) Replaced thermal adhesive on back of Mosfet

6) Invested in hot air SMD soldering station

here's some pics. I will update with the results.
signal-attachment-2020-01-24-080340.jpeg
signal-attachment-2020-01-24-082544.jpeg
signal-attachment-2020-01-24-082415.jpeg
signal-attachment-2020-01-24-065518.jpeg
signal-attachment-2020-01-24-080407.jpeg
signal-attachment-2020-01-24-080340.jpeg
signal-attachment-2020-01-24-080340.jpeg
signal-attachment-2020-01-24-082544.jpeg
signal-attachment-2020-01-24-082415.jpeg
signal-attachment-2020-01-24-065518.jpeg
signal-attachment-2020-01-24-080407.jpeg


Fingers crossed once ive replaced this little lot it will work again like a champ.
 
I have thoroughly investigated the fault i have had within the 400V controller resulting in Error 276 and ive found the following failed components inside.

1) Mosfet TR3 IXUS IXFL100N50P failed RS Components
2) Resistor R3 Cracked 68 OHM ordered Farnell
3) IC1 MCP6031E Shorting to ground between pins 3-6 and pin 4 Farnell
4) Blown LED Kingbright L-934LID 3mm Red.
5) Replaced thermal adhesive on back of Mosfet

6) Invested in hot air SMD soldering station

here's some pics. I will update with the results.View attachment 503882View attachment 503883View attachment 503884View attachment 503885View attachment 503886View attachment 503882View attachment 503882 View attachment 503883 View attachment 503884 View attachment 503885 View attachment 503886

Fingers crossed once ive replaced this little lot it will work again like a champ.

Mark,
What was the result?

This AM we had a few power spikes as a storm was passing through. I have two messages:
V_ess too LOW at the END of precharge
V_ess too HIGH at the START of precharge
(emphasis added by me)
These seem opposite of what the RC precharge circuit would yield. But...?

And/or... Can "TheFortunes" thefortunes could offer advice...?
 
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Mark,
What was the result?

This AM we had a few power spikes as a storm was passing through. I have two messages:
V_ess too LOW at the END of precharge
V_ess too HIGH at the START of precharge
(emphasis added by me)
These seem opposite of what the RC precharge circuit would yield. But...?

And/or... Can "TheFortunes" thefortunes could offer advice...?
It's been a while since I've been in the PEM so I'm just going to throw out ideas for discussion based on my experience (and fuzzy memory)...

1) We definitely had problems with the precharge circuit and traced it back to the IGBT on the CIC I/O board (the one with it's own heatsink) which had shorted. Without that circuit functioning the car would not charge.

2) We also had blown at least one of the capacitors

Sorry I don't have any more info, it's been a while and we replaced a LOT of components.

I would start with the IGBT on the CIC I/O board - it probably took the brunt of the spike and shorted.