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Discussion Starter #1 (Edited)
Hi TCCA,

Please excuse me (and advise) if I've posted this topic elsewhere earlier. I know I personally talked to a couple of the local parts houses about this, but I can't recall if I posted it here. I don't see it in my "Conversations" either. Here's the heads-up :

A couple weeks ago (~ end of August) I was diagnosing why our 2000 SES Duratek (~80k) would randomly have a flat battery in the morning every week or two. Without getting into the reasons for that, part of my debugging was to check battery voltage every morning. I was looking for a flat battery, before trying to start the car. To my surprise, I found that the battery was noticeably warmer than other engine parts in the mornings. And this is every morning, and not any morning where there was a flat battery.

I used a laser thermometer and found that one morning the battery temp was 96.8F yet the adjacent engine parts were 85.0F. Another morning the battery was 87.1F and the adjacent engine parts were 83.5F. Btw, the car was returning from work later in the evenings, but everything should have been cooled down to ambient temperature by mid-morning. I finally figured it out.

At first I thought it had something to do with that OEM battery case cover/shield acting like a blanket, so I removed it (and it's off permanently now too). That lowered the morning battery temps, but they were still not at ambient temperature. I also pulled the battery cables and checked between those cables for a closed circuit (ie. something is ON), but it was a zero ohm open circuit as desired. Then it hit me. What's inside a battery? Water and lead plates. What would make a good heat well? A box of water, packed with lead, and thermally isolated in a thick enclosed plastic box.

There you go, that's my answer. The battery was warmer than surrounding parts because it was retaining heat from the previous day. Maybe you won't experience this anomaly in northern climates, but (imho) it's possible in southern climates when the daily temps are in the high 90'sF and nighttime temps are still in the mid-80'sF. That's my story and I'm sticking to it!

Btw, feel free to jump on my theory and marketing opinion of one here. Comments, corrections, opinions, general BS, etc are always welcome : )

Regards . . .

P.S. I forgot to mention that I checked that same battery for temperatures with it sitting on a bench in a closed garage (which gets up to ~95-100F in the day, and no hot motor to make the battery hotter). One day it was 79.6F late in the afternoon, and 78F the next morning. Next day it was 80.8F late in the afternoon, and 79.8F the next morning. So we see maybe a degree hotter in the late afternoon, just sitting there disconnected. But certainly not the 5-10 point spread I saw with the battery located in the engine compartment of an active vehicle.
 

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I am thinking an engine block will hold heat longer than a battery. I believe the issue is the laser thermometer that you are using. I have used these devices in an industrial setting and on more elaborate devices you need to set the the device to the heat reflective properties of the surface you are looking at. A shiny silver surface will read a different temperature that a dull black surface even though they are the same temperature.

Here is a decent article that explains the issue. https://www.flukeprocessinstruments.com/en-us/service-and-support/knowledge-center/infrared-technology/what-is-emissivity
 

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Discussion Starter #3
Hi Automender12345,

Sorry for the delayed reply (I've been having other issues with my bull).

Thank you mucho for the intro to "Emissivity" and how those laser thermometers work. I read your link and also found this one that shows values for non-metals if anyone's interested:
https://www.flukeprocessinstruments.com/en-us/service-and-support/knowledge-center/infrared-technology/emissivity-non-metals

I need to move on for now. If anyone in the southern states (where it gets into the high 90's in the day and stays in the 80's range over night in the summers) ever stumbles onto this thread, please let us know if your battery is warmer the next morning than the surrounding engine parts/hoses.

Regards . . .
 
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