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Powerwall 2 fans at high speed...why?

bmah

Moderator
Supporting Member
Mar 17, 2015
4,361
8,480
Lafayette, CA, USA
Can anyone think of a reason (other than heat or system startup) that some (but not all) of the fans on a multi-PW2 system would running at full speed?

I have a Powerwall system consisting of 3 x PW2 and 1 x Gateway 1. They're hanging on the wall inside my garage. Inside temperature is about 70-75F. Everything's been working great since commissioning in March 2019. The gateway is running software 21.20.6, in time-based (formerly "cost savings") mode with 30% reserve. I'd like to believe that based on 2.5 years experience and having written my own measurement gathering software, I know what constitutes normal behavior for this system.

When we headed out around mid-day today, I heard a loud fan noise in the garage. A bit of investigation showed that the fan on one of the three PW2s (but only one of them) was running at a high speed. The only time I've heard it running this fast was during initial setup / commissioning. When we came back a couple hours later, the fan on that unit was back to normal but the other two PW2s were running their fans at flank speed. Eventually both of the other PW2s went back to normal. Everything's quiet now.

During this whole episode, the PWs were charging from solar as they do pretty much every single day. By time we came back the batteries were 100% charged and the solar was backfeeding the grid. It's neither particularly hot nor cold in the garage at the moment. The energy graphs in the Tesla app, as well as my own Grafana dashboards, show nothing out of the ordinary.

I'm a little mystified as to what's going on. Any ideas?

Thanks!

Bruce.
 

JPP

Active Member
Feb 4, 2013
3,076
1,325
SF Bay Area, CA
Can anyone think of a reason (other than heat or system startup) that some (but not all) of the fans on a multi-PW2 system would running at full speed?

I have a Powerwall system consisting of 3 x PW2 and 1 x Gateway 1. They're hanging on the wall inside my garage. Inside temperature is about 70-75F. Everything's been working great since commissioning in March 2019. The gateway is running software 21.20.6, in time-based (formerly "cost savings") mode with 30% reserve. I'd like to believe that based on 2.5 years experience and having written my own measurement gathering software, I know what constitutes normal behavior for this system.

When we headed out around mid-day today, I heard a loud fan noise in the garage. A bit of investigation showed that the fan on one of the three PW2s (but only one of them) was running at a high speed. The only time I've heard it running this fast was during initial setup / commissioning. When we came back a couple hours later, the fan on that unit was back to normal but the other two PW2s were running their fans at flank speed. Eventually both of the other PW2s went back to normal. Everything's quiet now.

During this whole episode, the PWs were charging from solar as they do pretty much every single day. By time we came back the batteries were 100% charged and the solar was backfeeding the grid. It's neither particularly hot nor cold in the garage at the moment. The energy graphs in the Tesla app, as well as my own Grafana dashboards, show nothing out of the ordinary.

I'm a little mystified as to what's going on. Any ideas?

Thanks!

Bruce.
Wow---coincidence. I have 2 PW2 in my garage (installed over a year ago) which seem to work fine. No errors, no issues. Was in the garage today around 1:00 pm (PWs fully charged from PV and theoretically should be idling). 1 of the 2 PWs was making gurgling noises and the fan was running full blast. The other was quiet. I put in a service ticket on the app. I wonder if the coolant level is somehow too low (no puddles on the floor).
 

bmah

Moderator
Supporting Member
Mar 17, 2015
4,361
8,480
Lafayette, CA, USA
Wow---coincidence. I have 2 PW2 in my garage (installed over a year ago) which seem to work fine. No errors, no issues. Was in the garage today around 1:00 pm (PWs fully charged from PV and theoretically should be idling). 1 of the 2 PWs was making gurgling noises and the fan was running full blast. The other was quiet. I put in a service ticket on the app. I wonder if the coolant level is somehow too low (no puddles on the floor).

Interesting!

Just looked, my garage floor is dry. I'm guessing there isn't anything like a dipstick for checking coolant level?

Perhaps some kind of reboot or diagnostic after a software update?

That's possible, but my data logger doesn't show any of the discontinuities that would normally happen if the gateway reboots. I wonder if there's some kind of software update that only affects the PWs but not the gateway?

Bruce.
 

BGbreeder

Member
Jun 19, 2020
492
293
Bay Area
Certainly sounds like odd behavior, and I think the lack of synchrony between when they were at "flank" speed the oddest bit. I haven't heard my fans since commissioning, either, but a much shorter baseline.

Mine were quiet all day. It wasn't that warm today, here or in Lafayette.

All the best,

BG
 

bmah

Moderator
Supporting Member
Mar 17, 2015
4,361
8,480
Lafayette, CA, USA
Any change the inlets are clogged? Might have to take the covers off to see?

Thanks...hmmm..."take the covers off" is not something I'm real anxious to do. If I look at the inlets there's nothing obvious clogging them and I was able to feel the outflow on the other side of the PWs. Maybe I can shine a light in there or something for a better look.

(I remember asking the installers / service people if there was a schedule or whatever for cleaning the filters but nobody could ever give me a answer.)

Bruce.
 

BGbreeder

Member
Jun 19, 2020
492
293
Bay Area
The right side is the intake and may collect debris. The left side is where the radiator is, and that may accumulate dust on the fins. Both should be readily visible with a bright light without popping the plastic covers, though that is easy to do. I do it with fingers by pressing down and out at the top, but a spudge Would certainly work better.

All the best,

BG
 

jboy210

Supporting Member
Supporting Member
Dec 2, 2016
5,685
3,685
Northern California
Thanks...hmmm..."take the covers off" is not something I'm real anxious to do. If I look at the inlets there's nothing obvious clogging them and I was able to feel the outflow on the other side of the PWs. Maybe I can shine a light in there or something for a better look.

(I remember asking the installers / service people if there was a schedule or whatever for cleaning the filters but nobody could ever give me a answer.)

Bruce.
Hopefully you can figure out what the issue is and fix it yourself. But just in case, Energy service requests can take a while before they send someone over. You might want to put in a service request now and if you fix the issue before they come out cancel the service request.
 

wwu123

Member
Apr 11, 2017
435
364
Silicon Valley, CA
Totally speculating, but could it possibly be some sort of regular but infrequent battery balancing or conditioning cycle, or to batter calibrate top-end battery level? We know from the car side of this forum that it helps re-calibrate the battery level to occasionally flex the SOC from low to close to 100% once in a while, perhaps Powerwalls like the same? A brief rapid charge/discharge might generate a burst of heat? Where were the SOC levels during this time?

Way back in the day, I had a digital OBD gauge on early gen Prius's HV (high-voltage) battery. After a few years of seeing the HV battery only cycle between about 30% to 80% in normal use, I was stopped at a light when the engine suddenly revved up, and I saw the HV battery do a rapid charge up past 95% and then just as suddenly discharge back down. Folks on the main Prius forum concluded it was some sort of HV battery conditioning cycle that I was one of the first owners to ever instrument and observe firsthand, that most folks would never notice when it was happening otherwise....
 

eml2

Member
Sep 28, 2017
279
216
Massachusetts
Could it simply be the powerwall doing preventative maintenance on its thermal control system? See the release note for v1.23 (September 2018).

 

bmah

Moderator
Supporting Member
Mar 17, 2015
4,361
8,480
Lafayette, CA, USA
The right side is the intake and may collect debris. The left side is where the radiator is, and that may accumulate dust on the fins. Both should be readily visible with a bright light without popping the plastic covers, though that is easy to do. I do it with fingers by pressing down and out at the top, but a spudge Would certainly work better.

Thanks for the advice...I worked up my nerve and pried off the side panels with a spudger. Nothing obstructing the airflow in, and there's nothing on the radiator fins.

Could it simply be the powerwall doing preventative maintenance on its thermal control system? See the release note for v1.23 (September 2018).


Thanks for the research, that looks like it could be the reason! Well that behavior roughly matches what I observed anyway (kinda weird that they didn't all do it at once).

Bruce.
 

Electrph

Member
Aug 29, 2019
468
312
Central California
i have 2 power wall 2's also mounted on inside garage wall .. i have only had mine for a mere 10 months . I noticed as garage summer temps increased i began to hear fans on both power walls not often at highest speed but always in sync
anyway the last month or so i noticed one of the powerwalls (always same one) at times has fan running at moderate speed while other one is silent .. other times both are in sync again.
i assumed this was due to the one powerwall getting more heat from outer wall due to position of sun .. but your OP has me wondering now 🤔
 

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