Fuse holder nut was glowing RED!

Mike Mas

Solar Enthusiast
Joined
Feb 6, 2022
Messages
25
Hello - This is a common problem with 12 volt lithium systems running an AC unit. What happens is as the plastic body holding the lug heats up, it can loosen the connection. Once it's loose its a chain reaction where it will self-distruct.

Thanks Mike
 

corn18

Village Idiot
Joined
Sep 9, 2021
Messages
529
Hello - This is a common problem with 12 volt lithium systems running an AC unit. What happens is as the plastic body holding the lug heats up, it can loosen the connection. Once it's loose its a chain reaction where it will self-distruct.

Thanks Mike
By AC do you mean air conditioner?
 

Zil

Photon Sorcerer
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May 27, 2020
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Problems with quality materials are usually traced back to operator error.
 

OzSolar

Whatever you did, that's what you planned.
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What is this so hard to understand?
Power dissipated = Current * Current * Ohms. The current moving thru the resistance heats up the fuse element and it melts down.
Little Fuse document on temperature derating
I've been wondering about a quick and simple way to test for things like this. Not just loose connections but also bad crimps, faulty breakers and undersized wires.

Would taking the system up to a pretty good load then checking voltage drop across the entire system (battery + to inverter +) then across each component tell you something? IE: 3% voltage drop on ~25v system would be .72 volts x 100amps resulting in 72 watts of heat being lost across the entire system. Then you start looking at each component and find the main sources of the voltage drop. Perhaps you could find something within seconds rather than wait for things to start glowing. This is something that pretty much anyone can check with a tool they already have vs a FLIR that not only is expensive but pretty fragile I think.
 

Zil

Photon Sorcerer
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Using a volt meter. I use my auto-ranging multimeter. With the probes across the connection you can discover even the smallest voltage drop by running a load. I fire up the microwave through the inverter and check my electrical connections often. Quarterly Maintenance.
 

DJSmiley

Solar Addict
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Aug 13, 2020
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594
If you have access to a FLIR camera that would be even better. Run a high load and any bad connection, not only screw, but also crimp or crap switch, will show up very clear. Very small voltage drops are harder to see, since not all meters are accurate with very low voltages, and a voltage drop can be very small, and with a meter you can't sometimes test all connections properly
 

TampaSteve

New Member
Joined
Feb 10, 2022
Messages
19
I second the FLIR. When I wired a large inverter I somehow missed the fact that I had left a washer on a bus-bar, underneath a lug. It made a small difference and I doubt it would have ever been discovered except for the fact that it presented a little bit of heat on FLIR that made me suspicious.
 

OzSolar

Whatever you did, that's what you planned.
Joined
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Messages
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Location
Southwest MO
I second the FLIR. When I wired a large inverter I somehow missed the fact that I had left a washer on a bus-bar, underneath a lug. It made a small difference and I doubt it would have ever been discovered except for the fact that it presented a little bit of heat on FLIR that made me suspicious.
Would you have a make/model recommendation? The Klein TI250 is the closest thing to my price range that I'm seeing.
 

TampaSteve

New Member
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Feb 10, 2022
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Would you have a make/model recommendation? The Klein TI250 is the closest thing to my price range that I'm seeing.

Sorry, I can't really say. I have a super old FLIR still working from the stone age. Its so old the non-replaceable battery is dead and I have to use it with a battery pack, but otherwise its still going strong. Edit: Isn't the FLIR for Android or Apple LESS than the Klein 250 ???
 

Just John

Photon Sorcerer
Joined
Aug 15, 2020
Messages
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Location
AZ
The thermal camera I purchased has been extremely helpful with wiring and connections. Load it up to max current for 5 minutes, then point and find the hottest part. VERY helpful for finding cat hairs, BTW.
 

Aabshir

New Member
Joined
Mar 17, 2021
Messages
22
Actually fuses blow due heat. They are self heating. That hot terminal would take out the fuse, eventually.
My roof top AC had bad connection taking out the fuses.
I no longer own this home, I buy all my EXs a house. Now when I date the first thing I ask: Do you want a house?
This had me laughing hard.
 

OzSolar

Whatever you did, that's what you planned.
Joined
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Messages
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Location
Southwest MO
This had me laughing hard.
Me too! Not sure why but it reminded me of something my doctor told me after I bit my tongue so badly it was still bleeding hours later. The scoundrel told me there's wasn't anything he could do and that "all bleeding eventually stops".
 
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Just John

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Batvette

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Feb 25, 2021
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Sorry, I can't really say. I have a super old FLIR still working from the stone age. Its so old the non-replaceable battery is dead and I have to use it with a battery pack, but otherwise its still going strong. Edit: Isn't the FLIR for Android or Apple LESS than the Klein 250 ???
Ive had the seek thermal for android for a few years now it was a disappointment for spotting wildlife or people at much of a distance but adequate for household utility use.
Paid for itself when a cheap chinese 12v freezer had leaky lid seals, I took an image of it showing the blue pouring out against a black and white background. Amazon quickly gave me a full refund and let me keep the freezer. It really highlighted it was a real issue.

The one I have is the XR its like $220.
 
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