why is my bolt on fuse getting to warm

oldcat

Solar Enthusiast
Hi i have a bolt on fuse on my charge controller on the battery... with a 4 gauge wire 6 foot long and the fuse only get awful warm just at the bolt im using to connect the 2 ware the 2 crimps are good they are not getting warm.. i also clean the 2 brass ends where they connect.. im using a 5/16 bolt&nut .. i only have 60amps going thru the wire... the wire chart shows you can put 200 amps throgh a 6 foot 4 gauge wire.. and i have a 70 amp Bussmann AMG High-Current Stud Mount Fuse i just want to no why.. or am i not seeing things not right here all help would be appreciated.. thanks.. my system is 12 volt..
 

smoothJoey

SmooJo
Hi i have a bolt on fuse on my charge controller on the battery... with a 4 gauge wire 6 foot long and the fuse only get awful warm just at the bolt im using to connect the 2 ware the 2 crimps are good they are not getting warm.. i also clean the 2 brass ends where they connect.. im using a 5/16 bolt&nut .. i only have 60amps going thru the wire... the wire chart shows you can put 200 amps throgh a 6 foot 4 gauge wire.. and i have a 70 amp Bussmann AMG High-Current Stud Mount Fuse i just want to no why.. or am i not seeing things not right here all help would be appreciated.. thanks.. my system is 12 volt..
please include a picture of the breaker as installed.
 

oldcat

Solar Enthusiast
here is the best i can do. i have 4 6volt crown 205 battery hookup as 12 volt.
 

Attachments

  • fuse 1.jpg
    fuse 1.jpg
    455.6 KB · Views: 59

brewmatic

Solar Enthusiast
Do you have a still washer between lug and battery? If so it could be a reason for heating. Non copper/aluminum washer should be placed only between lug and nut.
 

oldcat

Solar Enthusiast
no washer between lug copper on copper and is real tight ..this isn't making no sense....
 

DerpsyDoodler

Photon Sorcerer
To clarify, the fuse needs to be in direct contact with the cable lug. fuse holder -> fuse -> cable lug -> washer -> lock washer -> nut
 

HRTKD

Boondocker
Maybe it's just the angle of the picture but the cable end of the fuse looks higher than the battery terminal end of the fuse.

Otherwise, I agree with the prior comments that the connection is probably the issue. Bussman is usually good stuff as long as you have a real Bussman product and it is appropriate for your situation. I don't know anything about that fuse type.
 

oldcat

Solar Enthusiast
are you saying i need a fuse holder for this agm..... fuse is in direct contact with lug. washer is on the back side
 

HRTKD

Boondocker
Most of us don't have fuses directly attached to a battery/cell terminal. Instead, the cable goes to a fuse, then to a common bus bar. The common bus bar simplifies the connections and makes for a cleaner install.

The fact that the fuse is getting hot to the touch is a yellow/red-ish flag. Something may need to be changed if too much heat is being generated.
 

Boondock Saint

Solar Addict
The other folks have tried to provide examples of known goods based on sound principles ie: fuse holders, bus bar etc

"why does stuff get warm?" > resistance or poor connection

"how I can mitigate/improve a poor connection?" > provide smooth clean surfaces and increase the total surface contact area

"how can I increase the contact area?" > use large smooth clean washers, use sufficiently sized busbars, use fuse holders

"anything else?> Yes, don't over torque the bolt and nut to the extent that it causes the shape of the washer or terminals to deform or bow

clean, shiny, smooth, large


.
 
Last edited:

oldcat

Solar Enthusiast
i had no problem with heat on this when this was bolted to my battery before i put this fuse inline if i take the fuse out no heat but that not safe.
 

Short_Shot

Photon Sorcerer
i had no problem with heat on this when this was bolted to my battery before i put this fuse inline if i take the fuse out no heat but that not safe.
Then your connection to the fuse is poor or the fuse itself is poor.

Try taking a bit of sandpaper to the mating surfaces and clean it up real nice.
 

Hedges

I See Electromagnetic Fields!
i only have 60amps going thru the wire... and i have a 70 amp Bussmann AMG High-Current Stud Mount Fuse

Could be just the fuse causing heating. Can you determine if fuse element is at least as hot as the terminal? And how hot is "hot"?

60A/70A = 86%, a bit above the 80% recommended for continuous use.
 

oldcat

Solar Enthusiast
it just the bolt & nut--- getting warm not the fuse and i already clean with sand paper.and still on go the bussman fuse looks legit and im only putting 60 amps thru it.... this is dumb the fuse is new.... i guess the fuse is no good............
 

Hedges

I See Electromagnetic Fields!
Bolt and nut shouldn't be carrying any current to speak of.
Fuse terminal and ring terminal clamped together should have current flow through their contact (no washer or anything else in between.)
If fuse element is cold, and bolt on battery is cold, that leaves crimp connection as one last possibility. But I think you said nothing got hot before the fuse was installed.

Is the fuse element exposed, where you can check its temperature? Plastic body might not be so hot due to thermal insulation and heat loss to air.
At 85% of rating, some temperature rise of the element is to be expected. They are "thermal" fuses.
 

wholybee

Solar Addict
are you saying i need a fuse holder for this agm..... fuse is in direct contact with lug. washer is on the back side
Yes, the type of fuse in the picture must have a holder. The fuse is not meant to support wires without both ends of the fuse bolted to studs. For a fuse that CAN be mounted directly to a battery (still with a holder though) google "mrbf fuse"
 

oldcat

Solar Enthusiast
this is a stud mount fuse and it should have work just fine on the copper on copper lugs with a bolt .. i took it off and no more heat..
 

Attachments

  • fuse.jpg
    fuse.jpg
    620.8 KB · Views: 14

DerpsyDoodler

Photon Sorcerer
this is a stud mount fuse and it should have work just fine on the copper on copper lugs with a bolt .. i took it off and no more heat..
Maybe its poor quality? Where'd you buy it? can you exchange or get a refund? if its causing too much resistance/heat, its unusable.
 

sunshine

Solar Addict
Not an expert but...
Isn't that a fusible link that gets hot, until it gets so hot it melts?
Some have a very narrow range, some don't.
That is a very bad position. They should be in a position so when they blow there will be no collateral damage.

...and just as I was about to say do you really need a fuse between your cc & battery
i took it off and no more heat..
 
Top