Traction battery fan

Old thread, but I've been monitoring HV Battery Fan Speed and wanted to throw up some of my charts to add to the conversation.

It appears that the Fan comes on as soon as the Traction Battery Temperature reaches 97F (according to the #2 PID for battery temp). As others have said, if the battery temp is above 97 (or 100 as another poster suggested), the fan is on, if the temp is below 97, it's off. Always.

Figuring out exactly what conditions cause the fan to enter modes 1-6 is much more complicated. It depends on ambient air temperature at a minimum, but could involve other factors as well. My data suggests that vehicle speed is not a factor.

The first chart below shows MAX, MIN and AVG Traction Battery Temp (#2) by fan speeds. As you can see, 97 degrees is the on/off point. The second chart shows battery vs cabin temp - there is much less to be learned from that.

FANSpeed by bendertj, on Flickr

Next chart shows fan speed vs vehicle speed. Again, not much of a pattern there.

FANSpeedCarSpeed by bendertj, on Flickr
This final chart shows how often the fan is operating in each mode. This data was collected over the past month while ambient air temperatures ranged from 50F to 95F.

LVLpie by bendertj, on Flickr

Great stuff, thanks!

Ditto

Actually made an interesting discovery today. Climate control fan speed directly and immediately changes hv blower speed. Assuming battery temp is above 97, and AC is off, having the cc fan set >0 puts the hv blower speed at 1. Turn the climate control off and the blower speed increases.

This was very preliminary stuff, but 100% repeatable. Next step is to collect more data to see how it works in different conditions and when the AC is on.

I suspect there is a pattern based on cabin temp and climate control settings which dictates when hv blower speeds 1-6 are used. Getting closer to solving the mystery.

Too bad its getting cold and it will be harder to collect meaningful data.

I have observed the same as you above. It appears to me that the HV battery fan speed is affected by a combination of outside temp, cabin temp and AC controls. Good luck in solving the problem.

I always wondered why the extended PIDs included set temperature for the climate control system as well as the CC fan speed. Never in a million years would've guessed those had anything to do with HV blower speed settings, or anything really. At this point, I'm tracking the following PIDs (plus more) which theoretically could impact HV blower speed:
AC power
AC gate status
Cabin Temp
Climate control temp set
CC fan speed
Ambient Temp
HV Intake Temp
HV Battery (2) Temp
HV battery current value
State of Charge
HV blower speed
Inverter coolant temp
OBD vehicle speed.

I suspect State of Charge has a pretty strong impact on 1-6 mode speed. Yesterday my blower hit 4 for the first time all week, when the SOC was above 75% at startup. as the charge was discharged and SOC returned to 60% the fan speed slowed to 3 then 2 while the CC was off.

Gathered data this morning but HV battery never got above 88F.

Tim,

I have been monitoring the following all summer since we see 95-100F days and my car sits in an open asphalt parking lot all day:

Cabin Temp
HV Battery fan inlet temp
HV Battery temp sensor #2 (middle of pack)
HV Battery fan speed mode

I have not gotten nearly as detailed as you but I have seen where the battery fan speed does not follow just the battery temps. It definitely appears much more sophisticated. I have seen on a hot day with battery temps in the 105F range where the fan speed has been a 4. Then on a cooler day with cabin temp a little lower the fan speed has just been a 2 or a 1 with the same battery temp again at 105F.

I have wondered whether it could be based on rate-of-rise of temps but again it appears more sohisticated. I am like you and think the system monitors a lot of internal inputs to determine the fan speed.

Dwight

The average person may wonder why they need such a sophisticated algorithm to determine a fan speed but they are clearly shooting for the least amount of energy to do the job. Love it.

How about recirc vs fresh air setting?
You would think that fresh air setting puts positive pressure in the cabin and produces flow in the battery area.

Possibly, but two problems: 1) There doesn't appear to be a PID for that function so that we can log the data and analyze. 2) rhetorical question - why would fresh air vs. recirc matter? I actually applaud your creative thinking here. if there's not a PID, then there's no way the ECU could monitor it to adjust fan speed. Maybe the PID exists and it hasn't been discovered yet - don't know. if it was available, i'd be tracking it.

I though about the possiblity of window open/shut phase maybe affecting fan speed. Again, no PID and no reasonable reason why it would matter because how would the ECU determine that the incoming air would lead to reducing the batt temp?

The more I think about it, the more confusing it becomes. Especially because Toyota could just assume that 99.9% of Prius owners (except F8L - lol) are going to keep the cabin temp between 65F and 85F throughout the year - well below the 97F battery temp that triggers the fan to turn on. and the prius has a sensor that monitors cabin temp, so why not just adjust fan speed based on HV battery temp and Cabin temp?

I think this whole fan speed thing will be explained eventually, and it will all make sense, but for now it's not making much sense to me.

I have noticed that until the battery fan kicks on at 97F there appears to be very little convection cooling from the cabin through the battery. The battery fan inlet temp remains just a few degrees lower than the battery temp. This even with the cabin temp much lower, say in the 75F range. Even at steady highway driving there is very little decrease in battery temps, if any.

As soon as the battery fan kicks on, even at the lowest speed mode of 1, the battery fan inlet temp will drop very quickly to just a few degrees above cabin temp. At steady highway driving you will begin to see a decrease in battery temps shortly after the battery fan kicks on.

I would have expected to see some battery cooling without the fan on, especially with the AC on and the cabin much cooler than battery temps, but that is not what I am seeing.

The area where the battery sits is so small and isolated from the rest of the cabin that it's hard to imagine any effect of still air on it. think of the trunk on a sedan during the summer - even on a long road trip with the AC on, that space never gets as cool as the cabin.

someone reported that the hot air around the battery is vented to the exterior of the vehicle inside the rear wheelwells when the fan is blowing. i've been wondering if highway vehicle speeds could create a vacuum that draws air out without the aid of the blower fan. but beyond that, there's really no expectation that the cooler cabin air would reach the battery without the use of the fan.

I wonder where that intake temperature sensor is located - probably not just behind the vent opening in the rear passenger seat.

Good point

I believe the intake temp sensor is in the ductwork between the rear seat vent and the blower fan but closer to the blower fan.

The PIDs do exist. Check out Air Inlet Damper Targ Pulse or Air Inlet Damper Actual Pulse:

RECIRCULATION: 19
FRESH: 7

From the NCF:

The Air Inlet Mode automatically shift from INLET to RECIRC when the A/C is turned on.

Vincent

Wow great info, thanks. What is the ncf?

Like I said above, fresh air setting should produce positive pressure in the cabin. I thought such pressure would force some air flow in the battery as the battery vents to outside. However, I just looked at the ventilation system again, and the battery air discharges to the spare wheel area and then air travels next to the 12V battery and the outside vent. Due to that open flow configuration, the positive pressure in the cabin will do squat for the battery.

It is the New Car Features and you can download from techinfo.toyota.com.

Vincent

Was doing some reading on hobbits website yesterday - he's already done insane amounts of research on this topic for Gen ii. great read - will try to post a link shortly