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2010 Tesla Roadster Sport PEM Humming

So a newer Roadster here and I have a question, hopefully you can help me out with.

2010 Tesla Roadster Sport.
I have not drove the car alot, But went for a 10 mile drive last night and noticed when I went out to the garage later in the evening it was humming from the PEM box.
This morning I went out and it was still humming.
I got in and it had a 12v Battery warning on the screen. I assume The PEM running is draining the 12V battery.
The PEM was warm to the touch this morning before the drive cycle.

Any advice would be appreciated! The battery was able to start the car as well this morning, But was low.
 

im4uttx

Member
Supporting Member
May 28, 2019
402
286
Spicewood, TX
If you can get to the diag screens, check the temps of the PEM, battery, etc. Did it charge OK? Full standard charge? With the key on can you see the current drain? After overnight the PEM should have cooled to ambient temp, so if it is still warm, something is keeping it active...but I'm not experienced enough with debug, so we'll have to wait for the experts, but providing more information will help.
 

gregd

Active Member
Dec 31, 2014
2,662
1,878
CM98
It sounds like the car is not going to sleep. Is the humming really coming from the PEM, or is it the coolant pump?

After a proper charge, the battery should be under 30C (it is actively cooled), and the PEM drop closer to ambient. What is ambient? If the battery is under 30C, the car should go to sleep, and the circulation pump should turn off. Opening a door will wake the car up, and turn on the pump.
 

im4uttx

Member
Supporting Member
May 28, 2019
402
286
Spicewood, TX
So everything is between 38 and 43C PEM is at 43, Charges Fines. Thanks for the info above! Very Helpful. Now to figure out what is staying on and why?
I think your ambient should be getting your temps cooler than that..

So, looking through the OVMSv3 for my roadster, my temps are battery 30C, motor 31C, PEM 33C, charger 33C, at ambient 31C. If your PEM and everything is at 38-43C, then it seems like something is definitely preventing it from cooling down. Could be coolant pump issue I suppose...is there coolant in the reservoir? is it "bubbling" normally?
 
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DeedWest

2008 VP & 2011 2.5 Sport
Feb 5, 2014
932
1,136
Dallas, TX
I suspect you’re hearing the coolant pump - not the PEM fan itself. In warmer climates, it’s common for the charge cycle to cool the battery to below 31C for sleep. However, it can increase overnight in a hot & humid garage after charging is complete. Since you mentioned 38C, that sounds like what happened here.

In the summer months, I leave the door to my garage in my house open so that it drops the ambient garage temps to a healthy amount. It’s peace of mind knowing my babies stay asleep. ;)
 
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As has been stated, it is probably just your coolant pump running, and everything is normal. However, the car does not have any heat exchanger to cool down the battery coolant unless the car requests a cool down and turns on the A/C. The only way the ESS gets cooled down from just the pump running is by radiating heat thru the hoses and other components of the system. But there is no fan blowing on any of those, and they are buried behind the bodywork, so it takes forever. 30C is 86 degrees F, so ambient temps need to be well below that for any cooling to take place, especially during the summer. The pump creates heat when running, and the battery temp will actually rise if ambient temps are near the mid 80s.

As the owners manual states: "The Tesla Roadster is designed to be plugged in when not in use." That will cool down the battery (best if 220V is used), and the car will shut down and "sleep". Every 24 hours it will wake up, top off and cool the battery.

If you don't like to do that, maybe this can help.
Manual battery cooldown mod - a cure for the Roadsters insomnia
 
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im4uttx

Member
Supporting Member
May 28, 2019
402
286
Spicewood, TX
Just to provide some real-life numbers, I pulled my OVMS car temps when I arrived home tonight...and just now after an hour+ on the charger...
Reading initial 1-hour
Ambient 40C 38C
Battery 33C 29C
PEM 52C 52C
Motor 78C 57C
Charger 52C 52C

Not positive about ambient temps in Colorado, but bound to be lower than here in Austin in 37C (100F). I would think after a whole night, unless the ambient temp is near 38C in the garage/charging area, the car should have been cooler than the numbers reported in the later response (38-43C).

From my data, it looks like my car cools the battery to ~29C as a general min temp, allows it to rise to 31C, then cools (heard the fans come on just now and checked the temp was ~31C). I'm charging at 16A/240V, so that could have something to do with my results. Standard charge, not range...
 

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