Inline fuse from battery to converter overheating / blowing

[jpich0001]

I had some issues while dry camping with this fuse. My first trip since taking over the trailer and I wasn't receiving battery power with brand new batteries. Found the inline fuse holder with a 40A blown fuse and replaced it with another 40A. Plugged my 3200W Firman Generator into shore power and it worked for a bit until the 30A converter fuses at the panel continued to blow several times. Finally, the battery stopped working and I found the 40A fuse at the battery melted. At that point I discovered that that should have been a 30A fuse and was able to cut out the 40A melted fuse and replace with a 30A fuse which also blew. When I got home I cut out the melted fuse holder (12ga wire) and replaced it with another one (14ga wire). This one seems to be working but it gets extremely hot and when I measure the voltage across the battery terminals while hooked up to shore power I am only getting 11.9V. It seems to be charging the battery regardless but with the wire getting so hot the 30A fuse is starting to melt. Are the wires heating up caused by the wire gauge getting smaller? If so, would 10ga wire with a 30A fuse prevent this from happening? I've attached a diagram of my fuse wiring because I've also read in other threads that the fuse was placed wrong on certain models. Is this how it should be wired?

[RoadrunnerII]

You should be using a minimum 10 gauge wire for a load that is very close to the battery as in less than 10 feet for 30 amps
Do a Google search on 12 volt DC wire gauge size
You know your max amps is 30.
With 12 volts DC as you get further away from the battery or converter the natural resistance in copper wire increases. When you use a small gauge wire will cause the wire to get hot trying to provide the power thru it because of the resistance per foot. Also using crimp inline connections also adds resistance.
This is over simplified explanation.
If in doubt hire a professional. Melting wires is a fire waiting to happen.

RoadrunnerII

[jpich0001]

Does anyone know what the wire gauge is of the original fuse holder supplied by Jayco?

[jpich0001]

I have replaced the inline fuse at the battery with one that has 10AWG wiring and that fuse is still overheating / blowing after 15+ minutes. If I unplug my shore power before the fuse blows I am able to power the trailer using only the 12VDC battery but I haven't seen it get above 1/3 full.

Talking to fellow campers, it is believed I should be able to run the battery down fairly low and only have to plug back in to charge it or run the Air Conditioner so I don't see why using the shore power to charge a low battery would cause any issues. Is there something wrong with the converter maybe sending too much power to the battery?

[Marcm157]

Originally Posted by jpich0001

I have replaced the inline fuse at the battery with one that has 10AWG wiring and that fuse is still overheating / blowing after 15+ minutes. If I unplug my shore power before the fuse blows I am able to power the trailer using only the 12VDC battery but I haven't seen it get above 1/3 full.

Talking to fellow campers, it is believed I should be able to run the battery down fairly low and only have to plug back in to charge it or run the Air Conditioner so I don't see why using the shore power to charge a low battery would cause any issues. Is there something wrong with the converter maybe sending too much power to the battery?

Have you measured voltage at the battery while plugged in to shore power? Is your converter set to charge LifePo4 batteries? The converter will put out a higher voltage if so. There still should be no reason why its melting that inline fuse. Have you tested the battery to make sure it is fully functional? Does the battery get hot?

Have you traced that wire and see if there are any breaks that may cause arcing? I am just shooting in the dark here but there has to be something wrong.

[jpich0001]

Originally Posted by Marcm157

Have you measured voltage at the battery while plugged in to shore power? Is your converter set to charge LifePo4 batteries? The converter will put out a higher voltage if so. There still should be no reason why its melting that inline fuse. Have you tested the battery to make sure it is fully functional? Does the battery get hot?

Have you traced that wire and see if there are any breaks that may cause arcing? I am just shooting in the dark here but there has to be something wrong.

Voltage Plugged into shore power: 13.1V (before the fuse blew)
Voltage with shore power unplugged: 11.7V (shortly after fuse blew)
Voltage with battery completely disconnected: 6.05V
Battery Model: AGM31T (100Ah 20Hr Rate)
CCA: 925
CA: 1050

How would I know if the converter is set to charge LifePo4 batteries?

I will trace the lines today and see if I can find any obvious breaks or damage.

[RoadrunnerII]

What year Model trailer do you have.
If it's a newer trailer the converter will have a switch to set for lead acid or lithium
Having a 12 volt battery at 6 volts is low and it could be bad.
I would pull the battery and have it tested at an auto parts store.
Disconnect from pedistal power before removing battery
Your battery has shorted cells in it. Converter is still trying to charge it but shorted cells will draw high amps.
Time for new battery.


RoadrunnerII

[jpich0001]

Originally Posted by RoadrunnerII

What year Model trailer do you have.
If it's a newer trailer the converter will have a switch to set for lead acid or lithium
Having a 12 volt battery at 6 volts is low and it could be bad.
I would pull the battery and have it tested at an auto parts store.
Disconnect from pedistal power before removing battery.
I'm leaning towards the battery being bad and possibly your converter is set wrong.

RoadrunnerII

The battery is brand new and was purchased only a day or two before the camping trip.

It is a 2015 Jayco Jay Feather. See attached picture of the fuse panel.

[jpich0001]

Originally Posted by jpich0001

The battery is brand new and was purchased only a day or two before the camping trip.

It is a 2015 Jayco Jay Feather. See attached picture of the fuse panel.

Sorry picture attached.

[Marcm157]

Originally Posted by jpich0001

The battery is brand new and was purchased only a day or two before the camping trip.

It is a 2015 Jayco Jay Feather. See attached picture of the fuse panel.

New = Never Ever Worked - Just saying...

[jpich0001]

Update: After blowing 2 or 3 fuses almost immediately after plugging into shore power, both at the panel Reverse Polarity fuse and the battery inline fuse, I switched to a different brand of fuse which may not be of as good of quality. I plugged the trailer into shore power and they held up.

-Before plugging into shore, battery voltage was about 5V
-After plugging into shore, battery voltage went to about 13.7V and inline fuse holder started getting warm and then hot
-As time went on while plugged into shore, battery voltage slowly decreased to about 12.25V and inline fuse holder started to cool slightly
-I unplugged the shore power multiple times throughout the process and the battery voltage was slowly increasing from 5v to 10.3V to 10.7V to 11.3V. I will check battery voltage again tomorrow and see if it's discharged and how much and then if I get the same results of blowing fuses or overheating them with a smaller voltage difference between the battery and the supply.

See attached pictures of the fuses that "held up." I say they may not be as good of quality because they got hot enough to melt the plastic but didn't blow which is probably a bad thing. I was monitoring the situation

[RoadrunnerII]

I would still get the battery load tested.
At 6 volts its already not in peak condition.
The converter will attempt to charge any battery staring at full bulk charge ie hi volt reading.
Load testing is the only way to confirm status of the battery new or aged

RoadrunnerII

[RoadrunnerII]

Also....
You state you are replacing the reverse polarity fuses in the converter as well
That means the battery is connected backwards.
reversed polarity. If that is the case no wonder things are melting
If you have it backwards
The battery is now damaged and you need a new battery

Just one other note
Trailers don't use the same battery cable colors as vehicles
Check your connections
The negative or ground for the battery will be connected to a metal frame connection

RoadrunnerII

[craigav]

When the reverse polarity fuse(s) blow, that means you have a wire crossed connected to the battery. Can you grab a picture of the wires on top of the battery? ~CA

[jpich0001]

Originally Posted by RoadrunnerII

Also....
You state you are replacing the reverse polarity fuses in the converter as well
That means the battery is connected backwards.
reversed polarity. If that is the case no wonder things are melting
If you have it backwards
The battery is now damaged and you need a new battery

Just one other note
Trailers don't use the same battery cable colors as vehicles
Check your connections
The negative or ground for the battery will be connected to a metal frame connection

RoadrunnerII

Definitely not connected backwards...the battery would not power the trailer at all if it was connected backwards. When I unplugged the shore power to check the voltage I also ensured that the battery was powering the 12V components in the trailer (side note: the battery gauge never went above empty which makes sense since I never got above 11.3V). The white cable which is grounded to the frame was connected to the negative battery terminal each time and the black cable to the positive battery terminal.

The fuse that blew and then melted was the 30A fuse on the left in my previous picture of the fuse panel.

Another observation: I've been testing the battery voltage since I unplugged it from the trailer (both negative and positive cables have been removed from the terminals) and it fell from 11.3V at time of unplugging to 11.0V about 30 minutes later and now 10.8V, so maybe the battery has gone bad...or is this normal?

[RoadrunnerII]

Get the battery tested

RoadrunnerII

[craigav]

You should check all of the wiring, also lookup the manual for your converter as all of the converter manuals I have seen state that the only way the reverse polarity fuse(s) can blow is because of a reverse connection (even if only momentary). That doesn't necessarily mean that all of the cables are reversed. I have also looked at multiple converter circuits and how they are setup in regards to the reverse polarity protection, and the only way those fuse could blow is for sure a reverse connection. Although the manual doesn't state this, if the converter reverse polarity circuit had shorted diodes that could cause the fuses to blow, although that would be extremely rare if ever as most diodes that short don't stay shorted and fully open up and that would mean the converter shorted out, at least partially.

In any case, check and recheck the wiring for something connected wrong. ~CA

[jpich0001]

Originally Posted by craigav

You should check all of the wiring, also lookup the manual for your converter as all of the converter manuals I have seen state that the only way the reverse polarity fuse(s) can blow is because of a reverse connection (even if only momentary). That doesn't necessarily mean that all of the cables are reversed. I have also looked at multiple converter circuits and how they are setup in regards to the reverse polarity protection, and the only way those fuse could blow is for sure a reverse connection. Although the manual doesn't state this, if the converter reverse polarity circuit had shorted diodes that could cause the fuses to blow, although that would be extremely rare if ever as most diodes that short don't stay shorted and fully open up and that would mean the converter shorted out, at least partially.

In any case, check and recheck the wiring for something connected wrong. ~CA

If any cable was reversed momentarily, would that cause the fuse to blow immediately? I am able to hook up my shore power for periods of time before any fuses blow and they seem to be overheating, not just an immediate blown fuse. The pictures I provided of the fuses that plastic melted over a period of time and neither of those fuses actually blew, I turned the power off because I didn't want them to melt into the fuse holders. I have checked all the wiring and there are no loose or exposed wires that I can find.

Could these problems be caused by either:
1) battery type: AGM31T (100Ah 20Hr Rate)
CCA: 925
CA: 1050

2) faulty converter sending too much current

[craigav]

Originally Posted by jpich0001

If any cable was reversed momentarily, would that cause the fuse to blow immediately? I am able to hook up my shore power for periods of time before any fuses blow and they seem to be overheating, not just an immediate blown fuse. The pictures I provided of the fuses that plastic melted over a period of time and neither of those fuses actually blew, I turned the power off because I didn't want them to melt into the fuse holders. I have checked all the wiring and there are no loose or exposed wires that I can find.

Could these problems be caused by either:
1) battery type: AGM31T (100Ah 20Hr Rate)
CCA: 925
CA: 1050

2) faulty converter sending too much current

If any cable was reversed momentarily, would that cause the fuse to blow immediately?


Normally the answer is yes, but the more in-depth answer is that the reverse polarity fuse(s) would only blow immediately if there was a direct reversal short circuit that exceeded the amperage of the fuses (and the battery had enough capacity left in it to exceed the amp rating of those fuses). So if you had for example 3 connections to the battery and 2 of them were correct but the 3rd connection resulted in a reverse connection (for that circuit) but that circuits resistance was more than that of a direct short (less current flowing) then you would experience what you are experiencing which is a high amp load that overheats the wires and may or may not blow the fuse(s). High resistance is similar to the 12v electric cigarette lighters where the element can get extremely hot but not enough current flows to blows its fuse. Somewhere in your system is a short as that is the only way these wires and fuses would overheat, and the only way the reverse polarity fuses can blow is with a true reverse connection. A reverse connection is similar to a short circuit in cases like this. The reason for the reverse connection that I believe you have is that there are diodes in the converter that act as a one-way valve that would only pass the current and blow the fuses if the current was\is reversed (otherwise the diodes block the flow of power in a non-reversed connection). I have discussed this point with others quite (different website) a while back and added that the only other possibility which would be extremely rare would be that the converter itself is shorted internally and in the reverse polarity circuit itself. You would have smelled smoke most likely if that was the case, and again, I have never seen that happen but I am familiar with electronics and understand that scenario could happen. Even if it did happen though, the overload would be internal to the converter and would not overheat any of the wires like you have occurring.

The battery isn't the issue at this point either (whether or not it is still good is a different concern). The reason it isn't an issue at this point is because the converter is limited in its design to how much output it has so even if the battery was completely bad, the converters output still would not exceed the amperage of the reverse polarity fuses, only the battery could do that (or perhaps jumper cables to another battery that is reversed).

I have extremely high confidence that you have a reversed connection still yet. Some thoughts of what I would check and if you could take a few pictures of the connections on the battery that may\would help. Keep in mind that at the battery many manufactures and many times use black for the ground and still yet for other connections they use back for the positive which adds to this type of issue. Usually with white and black connections the white is the negative (ground) and black the positive, however certain connections to the battery may not be that way and the black could be used as the negative connection.

I would suggest to take a photo(s) of the battery connections for reference if nothing else and then disconnect all the cables except the two largest ones and then test for issues (hot wires or fuses blowing, etc.), then add another pair of cables and retest, and then another (depending on how many you have). If any connection results in a decent size spark and the wires start overheating then that would be the connection causing the issue.

To re-emphasize, this type of issue isn't caused by a bad battery, and isn't caused by the converter, and can only be caused by one or more connections reversed. When I say "this type of issue" I am specifically speaking to an issue where the wires, cables, fuses, etc. overheat along with blowing the "reverse" polarity fuses on the converter fuse panel output side (one or more times).

Feel free to share more pictures if you like as that may provide me with enough information to be more specific. Do you also have a clamp style dc amp meter? That could be of value as well.

~CA

[craigav]

I will add as I thought about it, if the battery was so far down (which it may be now) to have enough current in it to blow the reverse polarity fuses then in that situation it is possible that there is not be enough power existing in the battery to blow those fuses. I would suggest to completely disconnect the battery and charging it back up from a separate charger if at all possible prior to doing much more testing.

I updated the previous comment to reflect this additional information, which you may want to re-read it again since I made the changes.

~CA