Traction battery cooling fan

@Mendel Leisk , I'm looking forward to getting those links.

When entering the X gauge, does the car have to be on full power mode (engine running) or just power mode (engine off)??

 

@Mendel Leisk, I was able to find and input the X gauge for traction battery fan speed and traction battery sensor#2 temp.

I will monitor the readings as I drive home tonight.

Thanks for the tip.

 

@Mendel Leisk , here's my observations

Scenario:

Outside temperature:

high 70s to low 80s Degrees Fahrenheit

9:00:5:30 parked all day under the sun

Initial startup:

BT2 at 90 degrees Fahrenheit (33.2 degrees Celsius

Fan at 0

Bat2 at 100 degrees Fahrenheit (37.7 degrees Celsius)

Fan at 2

Bat2 at 104 degrees Fahrenheit (40 degrees Celsius)

Fan at 3

Never got higher than 104 degrees Fahrenheit (40 degrees Celsius) but when I started driving, fan came on and stayed on until I got to my destination.

Would you consider these normal readings??

What is average bat temp 2 and average fan speed?

Anyone??

 

That sounds fairly typical.

Again, I found highest temps at startup when the car was parked for a short time, say 1/2 hour to an hour, after an extended drive, on a hot sunny day. Then I've seen around 45C and fan speed 4.

The battery temp more typically will level out around 35C, fan speed 1or 2. Even in easy highway driving, cool evenings. It seems typical for the battery to run significantly higher than ambient.

 

@Mendel Leisk

I guess my next question is, Once you start driving the car, the fan for the most part stays on whether it be at 1 or 2 or higher

 

Here's an older post with a nice chart showing the range of observed battery temps at each fan speed: Traction battery fan | Page 3 | PriusChat

Here are mine - I definitely have some weirdness at fan speed 1 (lots of high outliers). I wonder if those readings are correct, or if there's an issue with my measurements (I'm using an OBD2 wireless adapter + the EngineLink app on an iPhone 5).



Below are the ranges of battery temps I've seen for the last 30 trips. At startup, TB2 is usually 10-20 F higher than ambient. It will go up from there depending on how much current is going into and out of the battery (lots of starts and stops = hotter). The interactive version of this chart is located here (you can click on a trip to see the second-by-second changes in temp and fan speed).

 

Maybe with a "warm" startup? With a completely cold start, say after sitting overnight, I see battery temp right at ambient. We're garage stored fwiw.

I've disconnected the ScanGauge for several months now. There was a periodic issue with brake: warning lights and brakes going into a sort of fail safe mode. The dealership thought it might be due to the constant obd plug-in, so I'm going along with their hypothesis.

Thanks for the detailed graphs. Maybe there's other factors than temp, that would account for the outliers? Or sensor 1 and 3 variation?

 

This mornings observation

Scenario:

Car parked outside and it has not been driven since yesterday.

Outside temp: 63 degrees Fahrenheit
(17.2 degrees Celsius)

BT2 temp: 78 degrees Fahrenheit
(25.6 degrees Celsius)

While driving, BFM at 1 when BT2 at
97 degrees Fahrenheit
(36.1 degrees Celsius)

Almost positive BFM is dependent on Outside temperature and outside cool air intake.

 

That would be true if ambient were constant . When ambient is changing, the battery lags hours behind ambient. For example, the battery temperature will typically be below ambient on a late-morning start after a (usually) cooler night.

Solar heating is a factor, too, even though the battery doesn't heat as rapidly in the sun as the interior does.

 

i always suspected the software cheats and lowers the fan speed while going slower, so owners wouldn't hear it and complain about it.

 

That range was off the top of my head, across all starts. I have been surprised that when I park in the deck all day at work the TB2 (center batt reading) is still a bit higher than ambient. BUT we don't have to rely on my memory, because we have data! I have to go have a social life tonight , but I'll do some more analysis this weekend. My hypothesis is that the gap between TB2 and ambient is higher in the winter (lower ambient temps).

Definitely. I have a hypothesis that after a prior trip (battery is still hot enough for a higher speed) the fan speed "ramps up" from zero in the first few minutes of the next trip. We'll see!

 

Your visualizations are da bomb. How/when did you get started doing that kind of thing? Is there a tie-in with your work?

-Chap

 

That's likely, considering that the battery cooling fan won't need to run as much with the same current history, and also that the HVAC system is likely to be adding heat to the interior.

The start-up temperature differential you're seeing will vary with the time of day---assuming outdoor parking, typical temperature variation through the day, and a long rest since last shutdown.

 

Cool data Marlin! You aren't Bob's alter-ego are you (another data junkie on this forum)?

Likely an accurate hypothesis. Very occasionally I will get a brake warning light when my ELM327 is plugged in. This disables regen on the car, meaning it only uses friction brakes to stop. When this happens, I'll turn the car off, unplug the adapter, turn the car on, and then plug the adapter back in.

 

When installing my ScanGauge II in my old Gen 1, I had to request the alternate cable (which they sent out for free) that leaves a couple pins unconnected, just so that the ScanGauge's automatic protocol search didn't glitch the car by probing on a pin the car used for other things.

I've since moved the ScanGauge to my Gen 3, and figured I would try it with the original, all-circuits-connected cable and see what happened, and (knocks wood) no glitches so far.

I notice that the most recent version of the ELM327 chip has added features for making its auto-probing behavior less potentially disruptive than older versions.

-Chap

 

Back to @Ozark Man 's original question for a second... The best way to see what's happening with the fan and battery temp is to get an OBD2-reading device (ScanGauge -- or -- bluetooth/wireless dongle + mobile app -- or -- mini VCI cable + Techstream). General consensus seems to be that the fan will come on (speed 1) when the middle battery sensor (#2) hits 97 F.

The low-tech solution is to estimate when the battery might be over the 97 F threshold, then hold a tissue or napkin up to the vent in the back seat. If the fan is on, it should suck the tissue against the vent cover. If ambient is in the 90s, and you've been doing a bit of stop-and-go driving, there's a good chance the battery temp will get up to 97 F. But, that's still a guess.


Other questions:

Ha ha, I think you mean @bwilson4web? No relation (except for the data junkie part!)

Thank you so much for saying that! I can't take credit, because the software I use (Tableau) makes it really easy to make nice-looking charts right out of the box! I'm a business analyst in my day job, so making sense of data is something I (hopefully) do professionally. Regarding my car's data, I don't always understand what I'm looking at (in college, I got a B+ in electrical circuits by the skin of my teeth), but I enjoy exploring data and finding patterns.


Preface: all of my data is from a 2013 Prius two with 30-36K miles, between Feb-June 2016, primarily in the metro Atlanta area. "TB2" is the temperature reading from the middle of the battery (usually the highest reading).

Question: is there a relationship between battery temp and ambient temp at startup?
I pulled all trips that were the first trip of the day (cold start), and took the initial TB2 and Ambient readings for each of those trips. Although not a well-controlled study, most of these are my commute to work (around the same time of day, starting from a tree-shaded parking spot). As we would expect, there appears to be a positive relationship (higher ambient temp --> higher battery temp). Predicting battery temp is probably a very complex relationship involving battery-chemistry properties that are way over my head (and not in my dataset)! There is likely a time-lag relationship as @CR94 suggests (although I can't test that, since I only have data when the car is on).

I only had one observation (blue) starting from a garage/deck - not enough to draw any conclusions.

@Xterra72 's observations are in line with these (if you plotted them on this chart, they would fit in with the cloud of orange dots).




Question: is there a relationship between the difference (TB2 minus Ambient) and ambient temp? I.e., is the battery temp closer to ambient when it is warmer outside?
The relationship is weaker here, although we do see a somewhat negative relationship, as we expected. Observed differences from my dataset were mostly in the 10-30 F range (higher in winter than I remembered). I live in Georgia, so the range of observed ambient temps is fairly narrow.





Question: battery temperature range by fan mode - what's up with those high outliers?
Back in post #26, I shared a boxplot of TB2 ranges by fan speed. I had some observations where the battery temp was very high, but the fan speed was only 1.

Looking into the detail, all but two of those high readings at fan speed 1 were in the first minute of a trip. It does appear that there is a ~one-minute "ramp up" period, where the fan will start up at speed 1 at the beginning of a trip. Here are a couple of trips, for example, where the battery temp at startup was 100+. In each case, the fan starts the trip at speed 1, then ramps up to the appropriate speed after about one minute.

 

There is everything to be said for using great tools. By the same token, you can lay the best tools in front of a dozen people and you don't get equivalent results.

Seems like you're being well employed.

on your first try, even? I was just at my reunion a week ago and ran into the prof I'd had for E&M. Over the years, it seems I'm still his only E&M student to drop it on the first try and then retake it the next time it was offered. (I guess that means all the rest of his students either finished the old fashioned way in one try, or bailed and never went near it again.) But it paid off when I got to electronics, which it was the prerequisite for, and was graded alongside people who had only had it once!

Nice catch! I'm definitely looking forward to seeing more of your investigations around PriusChat.

-Chap

 

That's a very good "guess." Unless the trip is short, keeping BT2 that close (<7°F) to ambient seems difficult during any kind of driving, in any weather, without resorting to air conditioning.

When the car is parked, that "complex relationship" seems likely to be a composite of interior and under-car temperatures, mediated by the time lag. In operation, those same factors apply, plus the further complications of heating by charge and discharge currents (exothermic reaction, as well as I²R), and cooling by the fan.

 

I don't think it's possible, or desirable, to try to keep the battery near ambient temp. On an extended drive: in the last leg of a regular trip we often do, cool evening temps, the battery's invariably around 35C. I would think that's normal, somewhat akin to engine operating temp.