The cooling problems continue

[Anti_Climax]

So, at this point we've replaced:

• The AC compressor

• The AC compressor harness/pigtail

• Battery loop pump

• Coolant Filter X2

• Replace Chiller line X2

• Replace Chiller block

When I last picked it up the tech had been unable to get the battery to go above 86F. That's while it's in the 60's outside. They put it on their L2 charger and called me to come get it. They felt confident it was solved after the chiller block replacement.

By the time I got there it had finished charging and was at 100F - it would have kicked on the chiller at 97F. I took the freeway route home, putting about 25 miles on it and had it at 108F when it was plugged into my L2. Again, while it's in the 60s for ambient temp.

A half hour later, it had climbed to 113F and stayed there while charging for about 2 hours. After that 2 hours it ran the chiller alone for another hour, during which the temp dropped to 111F and I unplugged it so it could ACTUALLY cool off and stop wasting electricity.

So, at this point I need to charge on L1 anytime my battery is anywhere near the chiller trigger temp, or it will start running the chiller and somehow adding thermal energy instead of taking it away.

I have a feeling I'm going to need to pull the battery or otherwise test the coolant flow through different parts of the system to see if something has gummed up.

Anyone have recommendations for in-line flow meters? Is it possible to even "get to" the coolant channels on the pack if I go through the effort of pulling it out?

 

[triangles]

Sounds like you may have a dead pump or clogged coolant filter. the battery cooling passages are practically foil thin metal plates sandwiched between the cells in the pack. taking apart the pack would accomplish nothing.

The battery loop also goes thru the charger. there are any number of hoses you could undo to very coolant flow but that would make one hell of a mess.

 

[Heima]

So just off the top of my head, has a vacuum air purge/coolant refill been performed? A large air gap in the coolant line might prevent sufficient coolant flow to cool the battery.

Also, I noticed that in my FFE, the solenoid for controlling the valve for the chlller refrigerant gets substantially hot. Stupidly hot. Might that solenoid have burned out? Is it hot or cold when the battery is to be cooled? This is the black "cube" under the coolant bottle.

So when the thermal management is supposed to be cooling the battery:
Are the pumps running? Check requested speed and measured/actual speed.
Are the valves in the correct positions? Check requested position and measured/actual position.
Is the A/C compressor running? Check compressor speed.
Is there sufficient coolant in the loop? Listen for the coolant pumps to go from a whine sound to a high speed rattle sound and then back to a whine sound. An air gap in the pump makes the rattle sound.
Is the temperature really hot enough to justify the cooling mode? Check the coolant into battery temperature vs the coolant out of battery temperature. If there is a large delta, the thermal management system is probably working. If the two temperatures are similar but low, like ambient, or if the temperatures are similar but high, like around 105, then the thermal management system is probably not working. Either not necessary (too low) or something wrong (too high)

You can check these parameters with forscan.
Good Luck!

 

[Anti_Climax]

The second filter replacement was one of the most recent things done. The solenoid has been checked this time and the previous. No indications of cavitation. Compressor turns on fine. The chiller and line are cold. Valves and diverters signaling as expected. No large delta, just "high". When it gets warm out for real, the car will stop giving me AC in the cabin because it's trying fruitlessly to get the battery temp under control. In the dead of winter I was actually able to get the battery hot enough to throw a "stop now" warning. The pump is running and the coolant has been totally drained and refilled by the dealer at least twice.

I figured, if I can hook into each end of the battery I could measure the actual flow rate and possibly back wash the coolant channels if they can't otherwise be serviced. Hell, if I can measure actual flow rate through the loop I'll be able to infer a lot more about what's happening. The pump and filter don't feel particularly cold - if not for that being the case before and after the filter swap if think it was the cause, but that's specifically why I had them change it.

Anyone know the locations of each temperature probe?

 

[Anti_Climax]

@triangles - based on what you know of those coolant channels - would you expect there to be any issues if the pump were run in reverse? I'm considering a backwash

Sounds like you may have a dead pump or clogged coolant filter. the battery cooling passages are practically foil thin metal plates sandwiched between the cells in the pack. taking apart the pack would accomplish nothing.

The battery loop also goes thru the charger. there are any number of hoses you could undo to very coolant flow but that would make one hell of a mess.

 

[davideos]

Not sure I have anything new to offer, but a few years back, my HV batter failed and I got a replacement. The dealer forgot to put in coolant. If I recall correctly, this was around August in So California. I ran like this for about a day without knowing, so no issue with the battery getting hot. The only issue I had was when charging. With my OBDII scan tool, I saw the charger temp get up to 150C and then it would throttle the charge rate and then fail to charge.

Although it took me longer than I care to admit to see there was no coolant, I made a few observations. 1) as mentioned earlier, the coolant pump would run while charging and make a louder sound....not completely obvious, but made me think, is it suppose to make that noise. And at one point, I thought the pump might be bad.

Once I discovered the lack of coolant, I added the orange coolant, but it took awhile to purge the air. Observation 2) there are 3 coolant loops and 2 of them have a "vent" line to the coolant reservoir. When the system is running properly, you should see coolant weeping through those lines and into the reservoir. If you don't see that when trying to change, then for sure, you have a blockage somewhere. Observation 3) try squeezing some of the coolant lines, there is a difference in the feel of a line filled with fluid and one that is empty. I believe that when I was trying to purge the air and I'd squeeze the hoses, I'd hear some gurgling from somewhere...the sound of air and liquid together. So you should hear any of that. I believe these coolant lines are the ones on the driver's side.

Eventually I took it back to the dealer and had them purge the air. There is no out-gas line from the cabin heater loop the coolant reservoir, so there is no way to get the air out when the loop operates independently.

Hope that helps somewhat.
Regards

 

[Anti_Climax]

At this point it has been emptied and filled a half dozen times trying to fix this. I could understand missing a burp once but having talked to the tech directly I can't imagine that would be missed every time. There's otherwise no indications of any voids - it's as if the coolant can not flow through the battery/charger loop at all. I'd think the pump impeller was bad or the filter was clogged if both had not already been fixed.

Now that I think about it though, the fact that there are separate paths through the upper and lower packs would practically rule out an obstruction in the battery itself. It would have to be somewhere before #14 and after #12 on that diagram, unless it's somehow clogged in both paths through the pack.

So I suppose my coolant channel question is moot unless I rule out all the other portions of the coolant path. At least that makes the search a lot easier.

 

[triangles]

I'm no expert, but I don't see any reason why a back flush would be bad. AFAIK it's just a bunch of very thin cooling plates sandwiched between cells.

 

[davideos]

When the battery loop is running (i.e. the pump), do you see fluid drizzling into the reservoir? At least that would indicate that the pump is working. You mentioned before about putting in a flow meter...but this would be a quick check to see that something is happening.

 

[Anti_Climax]

At this point it's been up on blocks for a few months, but I could feel and hear the pump running.

Where does the aspiration tube tap off the battery loop?

 

[Anti_Climax]

I got it warmed up to the point where it turned on the chiller and had the pump running at 50% and there is the tiniest dribble of coolant coming up from that side into the reservoir.

 

[davideos]

Sorry for the late reply. Yes, that's what I was talking about. There are two of these de-gas lines...I think that's what they call them. I believe the batter loop de-gas line is just under the "cover" and to the right side...drivers side. It is just behind a diverter valve. That line goes back toward the cabin, to the left, and the forward to the coolant reservoir. The second line is at the right side of the radiator and not the one you're interested in.

When mine was running correctly, there was a small stream of coolant coming out of the line. I would think it would indicate your pump is working. Although, it just means there is positive pressure at that point in the coolant loop.

However, when I did all this, and even took it to the dealer to purge the air out of the cabin heater loop, I did have an odd issue where the reservoir became completely full and pressurized. Air somehow got introduced into the system. I opened the reservoir and coolant came gushing out. I let it cool down, added replacement coolant and it never happened again. Anyway, I don't think that story has anything to do with your issue.

 

[Heima]

Don't know if this will help, but I just discovered this FFE thermal video:
https://www.youtube.com/watch?v=bJQ4N1QjnE8

 

[Anti_Climax]

I've already diagrammed it all out from the exploded views in the service manual - unlike that diagram in the video, I managed to get it all in a single plane with no crossings. Although I will be sanity checking it to see if I missed anything.

At this point I'm going to need to drain it and splice in several test valves that will allow me to isolate flow in the separate sections to see where coolant is getting blocked. There's no other reasonable cause I can think of. The compressor runs, the chiller cools, the pump runs (and has been replaced) and the filter behind it has been replaced twice.

Yet the temps I see when the car "runs" while fully charged and plugged in (so the electronics are all being fed from DCDC powered by output from the SOBDM instead of the battery) suggest that warm coolant is convecting up from the SOBDM toward the battery over time, which should not be happening if there was free flow of the coolant. At least that suggests the blockage isn't in that section either, so less to pull apart.

 

[Anti_Climax]

If anyone is interested in the schematic he has in that video, I think it's from this PDF

https://www.macheforum.com/site/attachments/lesson-3-cooling-system-pdf.3825/

 

[Anti_Climax]

I used the diagram in that video to sanity check the one I created myself and it doesn't look like I had anything out of place - though it did let me add stuff like the degas lines, temperature sensors and one-way coolant paths. I've created a planar diagram (no crossings) for folks to reference.



I may update this later with annotations on different lines like he has as well as color coding the loops. Diodes and arrows on my diagram indicate one-way coolant flow paths. The use of transistors was merely to have a symbol that allowed for a 3-way junction, though their arrow does indicate the direction of a known one-way coolant path wherever they appear. Text from his diagram reads as:

Priority Logic
A. Control Battery Circuit Temp
B. Control Motor Circuit Temp
C. Control Cabin Temp
D. Vehicle Performance/Range

MACS Circuit Cooling
ECO: Pump low-output directed to bypass conduit
Standard: Pump high-output directed to radiator
Cabin: Pump high-output directed to heater core (mild heat)

HVB, BCCM & BECM LOGIC
3 Cooling Modes:

First Cooling Condition: Desired temp Lower than Actual temp: Determine which condition is also present (2nd or 3rd condition).

Second Cooling Condition: Motor Circuit fluid tempt lower than desired battery temp. If yes, Cooling Mode A: Valve in 1st position to permit fluid flow from Motor Circuit to Battery Circuit. A/C OFF (no flow to chiller)

Third Cooling Condition: Motor Circuit fluid temp higher than desired battery temp. If yes, Cooling Mode B: Valve position #2 (Isolating battery circuit from motor circuit), Enable Battery Circuit Pump, A/C On (permitting flow through chiller)

Fourth Cooling Condition: Motor Circuit fluid temp equal to desired battery temp. If yes, Cooling Mode C: Valve in 1st position to permit fluid flow from Motor Circuit to Battery Circuit and A/C Chiller On. This allows coolant flow from radiator to chiller.

Cabin Heat
2 Heating Modes:

First Heating Condition: Warm fluid from MECS OUT re-routed to cabin heater core inlet. Outlet from heater core routed to MECS bypass (to cool MECS motor). heater pump low speed to avoid coolant flow to bypass heater core.

Second Heating Condition: Valve closed which recirculates heater.

 

[Anti_Climax]

Alright - I've gotten NTC thermistors spliced into the lines before and after the chiller block so I can look at the delta. I also have a flow meter looped in on the return to the diverter. When running in degas mode it shows something like 14L/min through it.

I've pinched off the return hoses and it seems the upper pack has a higher resistance to flow than the lower, but nothing to indicate it's fully blocked.

Does anyone have a description or pictures of the cooling path inside the battery packs?

Looking at E144689 in the service manual, the battery is individually tracking cell temps with the data passing on an internal CANBus. Does anyone know if the value it gives is the highest among the cells, a weighted average or something else?

Can anyone capture logs of their car showing their pump speeds, diverter settings, chiller solenoid, compressor RPM and coolant temps? I'd like to compare what I'm seeing and look for further clues.