Engine Bay Temp Data Logging Thread (1 Viewer)

[OregonLC]

There was some discussion in the the 'what have you done this week' thread regarding the temperature impact to Li batteries mounted under the hood. I currently have an X2Power AGM in the Slee bracket. I mounted a little data logger to the engine side battery terminal just to see what was going on. To be fair, this is a measurement of ambient temp at that location and not the actual battery temp, though one would assume that side of the battery would eventually equalize with ambient.

This particular run was over four trips, two 200 mile trips on either end with two 25 mile trips in the middle. The 200 mile trips involved mountain passes so the engine would have been working, though OAT was in the high 30's. OAT for the 25 mile trips would have been in the upper 40's to lower 50's.

The last trip that peaked at 144.3F peaked early. This was at 5pm traffic in the Stafford area of Portland, I-205 at rush hour. Stop-and-go, showing that low power slow is worse than high-power fast.

I suppose a better measure for the question at hand would be to have a sensor pad directly on the battery. So I wouldn't take this data set as being an accurate indication of what is actually going on with the battery itself, but rather the temp of the engine bay near the battery location.

Not really relevant to the battery question, but there were four days when I didn't drive at all. It was interesting to see the daily temp cycles. The warm up was steeper than the cool down each day. Don't know if that's because of the radiant absorption accelerating warm up (truck is parked outside and facing south) or if it's just how ambient cycles in the spring.

What is interesting with this curve is the insulation effect of the hood. On several of those nights the temp was in the mid-20s outside but it never got below 33F at the data logger.

 

[TeCKis300]

Great input and data!

I have a couple thermistors underhood that I reference between a SwitchPros and OEM MAF IAT sensor. I would agree with your findings. In low speed crawling, the temps spike pretty severely. Particularly with vehicle nose up. This is worse on a summer day at elevation. Some of the same scenarios when we see fuel boiling.

 

[OregonLC]

Great input and data!

I have a couple thermistors underhood that I reference between a SwitchPros and OEM MAF IAT sensor. I would agree with your findings. In low speed crawling, the temps spike pretty severely. Particularly with vehicle nose up. This is worse on a summer day at elevation. Some of the same scenarios when we see fuel boiling.

The ideal data point would be the internal battery temp. This is what Battleborn (and others) is using to regulate. So we're left, at best, with an external surface monitor. The IR cameras or guns are good for this, but only at a single point in time.

I would suspect that with some type of battery heat shield or blanket that heat could be minimized, however with as cool as it was during my runs I was surprised to see a temp in excess of the advertised battery limit (140F for Battleborn). Dakota has limits that are different depending upon what you click on.

I'm going to keep running data as we move toward summer. But as much as I'd like an under-hood solution for space management, a cargo-area install seems the most prudent for my use case.

From Battleborn:

From Dakota for 135Ah (135Ah FAQ):

From Dakota 135Ah spec sheet:

 

[bloc]

…the temps spike pretty severely. Particularly with vehicle nose up.

All of this is interesting, but that detail especially.

I assume it’s because nose up you’re generally climbing and therefore using more horsepower?

 

[TeCKis300]

The ideal data point would be the internal battery temp. This is what Battleborn (and others) is using to regulate. So we're left, at best, with an external surface monitor. The IR cameras or guns are good for this, but only at a single point in time.

I would suspect that with some type of battery heat shield or blanket that heat could be minimized, however with as cool as it was during my runs I was surprised to see a temp in excess of the advertised battery limit (140F for Battleborn). Dakota has limits that are different depending upon what you click on.

I'm going to keep running data as we move toward summer. But as much as I'd like an under-hood solution for space management, a cargo-area install seems the most prudent for my use case.

From Battleborn:

View attachment 3621340

From Dakota for 135Ah (135Ah FAQ):

View attachment 3621346
From Dakota 135Ah spec sheet:

View attachment 3621347

I've seen temps in excess of 167F underhood and they are in cooler spots. It can likely get hotter than that as I wasn't looking for peaks, but trying to debug a fuel pump issue at the time. To you point, the battery is a large mass which helps modulate peaks. The vehicle would have to be in the specific scenario for a long time (i.e. rock crawling and idling) to significantly elevate internal temps. Living in SoCal, I do that quite often where we're on foot for hours on sections trying to get a crew navigated over obstacles while my vehicle is crawling and or idling. Or just in traffic. I agree the heat shields or blankets can help.

All of this is interesting, but that detail especially.

I assume it’s because nose up you’re generally climbing and therefore using more horsepower?

The cars are barely idling over obstacles in low range so power may be a factor but possibly not a driving one. Unless it's sandy loose obstacles. It seems that convection and hot air rising, including off the underbody exhaust are big factors. A/C is running also in summer. Everything just gets hot and heat soaked as the radiator fan is trying to push air down through the engine bay and chassis but it all wants to come up and around.

 

[gluaisrothai]

All I have to report is no shutdowns yet from the Dakota. If I can find an economical way to put a probe on the battery surface with a data logger under the cooling shroud I will do so. The Dakota BMS does not broadcast battery temp to the best of my knowledge.

The battery cooling fan thermostat turns on at 40 C and is always on after 6-10 minutes of driving. Runs for about an hour to 90 minutes after shutdown. Hard to gauge how effective it is, but the theory is that the aluminum acts as a reflective heat shield while the cool air flowing behind the shield prevents re-radiation and air transfer.

 

[TeCKis300]

Runs for about an hour to 90 minutes after shutdown.

This is a great point. Some of the heat soak damage potential could be after shutdown.

 

[Fisher23]

Interesting.

AGM ODYSSEY Operating Temperature Range OD-40°F / -40°C to 176°F / +80°C
Battle Born Operating Temperature Range: -4°F (-20°C) to 135°F (57.2°C)

Many vehicles do not put the battery in the engine bay and put it in the trunk.

 

[gluaisrothai]

This is how Cessna cools their firewall forward starter battery installation. Blast air routed from the engine cooling baffles ducted through the 1” scat tube. I took a similar approach except I extended the shroud to cover three sides of the battery.

 

[daneo]

Renogy batteries can report temp sensor readings at each cell over Bluetooth. I haven’t wheeled in the desert since getting the Renogy, but I have been surprised that the reported temps have never even gotten to the “warning” temp, let alone the “shut down” temp. I’ve done sunny hill climbs in 90 degree heat.

This is all in a 4Runner, so slightly different setup.

Most of all I’m surprised at the delta between surface temp measurements folks are making and internal temps reported by the battery. Is there really that big of a difference?

Glad we’re all interested in collecting and comparing data.

 

[OregonLC]

Many vehicles do not put the battery in the engine bay and put it in the trunk.

From my understanding, this is done for space constraints or weight distribution (BMW) and is not related to heat. To the latter, somewhat ironic when you see drivers clearly 50 lbs over ideal weight that moving a batt to a different corner would be of importance, but such is the world we live in.

This is how Cessna cools their firewall forward starter battery installation. Blast air routed from the engine cooling baffles ducted through the 1” scat tube. I took a similar approach except I extended the shroud to cover three sides of the battery.

I like your creativity. The thing aircraft have going for them is the constant supply of cool air. Completely passive system; if it's flying it's cooling. Hill climbs in Moab in summer temps are a different animal. Interested to see your results as we move into hot season.

 

[gluaisrothai]

I like your creativity. The thing aircraft have going for them is the constant supply of cool air. Completely passive system; if it's flying it's cooling. Hill climbs in Moab in summer temps are a different animal. Interested to see your results as we move into hot season.

Exactly. That’s why I used a small blower with a thermostat control- which has the added advantage of running after engine shutdown to prevent heat soak. I pulled the trigger on a temp data logger with an adhesive mount k type thermocouple to take some measurements over the next few week.

 

[gluaisrothai]

Thermocouple and data logger in place. Right now the TC is just floating between the shroud and the battery. I have a second channel which I might tape to the side of the battery furthest from the engine.

 

[gluaisrothai]

I have the second TC in free air adjacent to the PS reservoir. The spots where the two curves come closer together was a brief freeway section. Generally the shroud seems to work well in keeping temps stable and quite a bit lower than underhood air temp at city speeds.

 

[UPR LC]

This is really cool, I love seeing real data!

 

[OregonLC]

@gluaisrothai you've probably already posted this elsewhere, but what did you do for your battery box? Custom made? Repurposed from something else?

 

[TeCKis300]

I have the second TC in free air adjacent to the PS reservoir. The spots where the two curves come closer together was a brief freeway section. Generally the shroud seems to work well in keeping temps stable and quite a bit lower than underhood air temp at city speeds.
View attachment 3628094

Good stuff! Toasty in there and box is doing a great job.

What was the ambient conditions and use case?

Looks like underhood has potential to get hotter still.

 

[gluaisrothai]

Good stuff! Toasty in there and box is doing a great job.

What was the ambient conditions and use case?

Looks like underhood has potential to get hotter still.

Toasty is right, almost burned my hands on the datalogger. 75F ambient, daytime, sunny, heavy traffic including in the Webster tube from Alameda to Oakland.

 

[gluaisrothai]

@gluaisrothai you've probably already posted this elsewhere, but what did you do for your battery box? Custom made? Repurposed from something else?

Hi- just 0.040” aluminum cut on a band saw and then bent using an el cheapo sheet brake.

 

[LC Mike]

Hi- just 0.040” aluminum cut on a band saw and then bent using an el cheapo sheet brake.

What fan and thermostat did you wind up using?