HELP - Melted Main 12v Fuse

[Byron Kinnaman]

Originally Posted by John in Santa Cruz

exceeding 30 amps would have blown the fuse. fuse holder melt downs are far more likely from resistance in the connections...

Not necessarily true. exceeding the 30 amp rating for x period of time might blow the fuse. Depends on time x and how much the 30 amp is exceeded.



30 amps is a lot of current to try and pump through a faulty connector. The but connectors or even the fuse blades with faulty connection can get hot enough to start a fire.

[Joe & Cherie]

Thanks for all the replies guys!! I'll post a pic tonight when I get home from work! Its a spade fuse green, and it plugs into what seems like a good quality rubber socket with a cap. Even the rubber is a tad distorted. Most of the melting is the green fuse body, and the fuse lugs are very discolored almost black. But I'll post a pic tonight for sure!

Good news is I turned on my 12v fridge at 6pm Monday with a full charge. Fridge still running strong this morning at 33* and 61% left on the battery. So fridge working great and battery draw as expected!

I should have felt the fuse but was in a rush to get to work. Tonight I will look at new fuse. Also, tonight I will plug camper into house to recharge battery and feel fuse after a few hours of charging. I'm sure that's probably the most amps the fuse sees is during charging.

I think I'll just replace the fuse holder with a good quality new one - probably will fix issue!

Your guys replies help a lot! I learn every time I log onto this site!!

[Raz]

Assuming a current of 10 amps flowing through the fuse were to cause a voltage drop of 0.7 volts, that would mean 7 Watts of power dissipation. With such a small surface area I would expect that to get very hot. I would replace the holder and fuse. As John suggested littelfuse or bussman are the best fuses.

One other thought, just because the converter manufacturer says 30 amps doesn't mean that's what will flow. Current is circuit dependent. My converter says 45 amps. I replaced the 30 amp fuse with a 20 amp glass fuse and use the easy to open holder as a battery disconnect. The fuse has never blown. The holder came from a marine supply place.

[Joe & Cherie]

Pics! I’d say a new fuse holder is in order lol.

[Joe & Cherie]

OK with the fuse holder cleaned up best I can get it and a brand new fuse installed I went ahead and plug the camper back into the house. The meter is now showing 13.2 V charging and 29.5 A charging. This is on boost mode. It surprises me that the volts are not at 14.4 per the booklet. The fuse holder and the new fuse are getting extremely hot. Too hot to touch. I think at this point I should just wait until I replace the fuse holder and then try again. Sound about right?

[Byron Kinnaman]

From looking at that picture I think there very good likely hood that you a defective fuse holder. A corroded fuse holder will introduce some unexpected resistance into the system. As was pointed it doesn't take a whole lot to equal 5 to 20 Watts of power. If you think you can hold on to 7 watts get an old Christmas 7watt or night with a 7 watt bulb and try hanging on to it.


5 ohms of resistance could create about 7 watts of power dissipated as heat.

[Civilguy]

Originally Posted by Joe & Cherie

I think at this point I should just wait until I replace the fuse holder and then try again. Sound about right?

The heat will be concentrated right where the resistance is occurring. It appears that the hot spot is located at the edge of the fuse holder.

Once you replace the fuse holder, you might be able to peel back the rubber and see what is not right. It appears to be a faulty connection where the wire joins to the female spade terminal underneath the rubber jacketing.

[Raz]

How are you measuring the 29.5 amps and are you sure it's charging. I would not expect to see that high a current unless you have a seriously dead battery. Is there anything wired to the battery directly that bypasses the fuse?

[Joe & Cherie]

Originally Posted by Raz

How are you measuring the 29.5 amps and are you sure it's charging. I would not expect to see that high a current unless you have a seriously dead battery. Is there anything wired to the battery directly that bypasses the fuse?

I do have a TM-2030-RV battery monitor installed in the egg. That is what is giving me the readings. When I push the button on the charger wizard, it goes into “boost mode” which maximizes the charger. When it was on “normal mode” it was showing about 13A.

The batteries are 225ah and are currently at 61% charged per the monitor. I ran my fridge for 36 hours on purpose to test it and the battery drain. Drained as expected.

It will be tomorrow night before I get to the Marine store and get a good fuse holder and new crimp connectors and battery connector.

I’ll report back tomorrow night after install and see if it gets hot again! I’m thinking it’s the issue but want to keep this thread alive till it’s over for my sake and anybody else learning with me!

Thanks again!

[gordon2]

Originally Posted by Raz

How are you measuring the 29.5 amps and are you sure it's charging. I would not expect to see that high a current unless you have a seriously dead battery. Is there anything wired to the battery directly that bypasses the fuse?

Agreed.. Based only on limited information, that amount of charging current sounds very high.

Furthermore, if you are going to be passing that much current, are you sure the fuse holder is rated for it? The similar in-line fuse holders I see on page three of this spec sheet are rated at either max 20 or max 30. None are rated for more than 30 amps. Perhaps you have a 20 amp fuse holder or even a 30 amp might be stressed. Maybe upgrade to a fuse holder on page two of the spec sheet?

I still wonder however if the converter and charge wizard should be putting out that much current. Its 30 amp max for charging AND running things in the trailer (at the same time) is it not? I have never seen more than 6-7 amps or so of charging current recorded by my TriMetric (from my PD 30 amp converter), and even that falls off pretty quick. (But that is for a single group 27 battery) Maybe a call to PD and ask what they think is going on.

Just thinking out loud here.

[John in Michigan]

Based on the sparse details provided in the documents at the PD website, in BOOST mode, the Charge Wizard will produce high enough current to charge a battery up to the 90% level in 2 to 3 hours. You said that you have 225ah battery capacity, so it does not surprise me that the converter charge wizard would put ALL of the PD9130 converter current (30 amps) into charging the battery. That means that you may need to switch to a higher rated fuse holder and fuse, and higher gauge wire.

In the example you used, you discharged the batteries by running the fridge. Then you attempted to recharge the batteries in BOOST mode. How far down did you discharge the batteries? If down to 60% capacity, then charging back up to 90% in 2 hours would require 67.5 amp hours (more than 30 amps), thus maxing out your charger in BOOST mode.

EDIT: In summary, I suspect your charging load is right at the limit of your fuse. Generally when designing, size the wire for significant margin (20-30%) above that value, so probably 40 amps. The fuse needs to protect the wire, thus 40 amp fuse.

[Joe & Cherie]

Yes I forced it into boost mode manually. I do wonder tho if it ever has been that high before automatically. I was 61% and it went to normal mode automatically. Then I pushed the boost button on purpose to test it out, and hot it got!

I had nothing else at all running. I did turn on a few lights and it dropped down a little. I think it’s working as should. I’ll get the new fuse holder in there tomorrow hopefully if the rain holds off. Then I’ll test it again. After camping season I’ll change out entire wire to 8ga and 40a.

[John in Michigan]

Joe,

- Another poster asked how you determined that the battery was receiving a 29.5 amp charge. I have the same question. ??

- Based on what you just posted (press the button to select BOOST mode, and then the fuse gets hot), its pretty likely the fuse and fuse holder are undersized. That being the case, don't select BOOST mode again until you upgrade the fuse and wire.

EDIT: I recommend you read the manual thoroughly. I thought I read that under certain circumstances, the charge wizard will automatically go into BOOST mode. If true, then you may continue to have an overheating fuse.

John

[gordon2]

Originally Posted by John in Michigan

Joe,

- Another poster asked how you determined that the battery was receiving a 29.5 amp charge. I have the same question. ??
..

He has answered this question (and here also). He has a TriMetric battery monitor. It uses a shunt on the negative side (first thing off the battery) and it measures the current going or coming from the battery (through the shunt). I have the same set up. More info at home - Bogart Engineering

[John in Michigan]

Thanks Gordon. I checked the Trimetrics 2030 specs but wasn't sure whether it provided that info. I did notice that it measures amp hours in and out. Also somehow indicates battery % charged, but I don't imagine that's particularly accurate.

[gordon2]

Originally Posted by John in Michigan

Thanks Gordon. I checked the Trimetrics 2030 specs but wasn't sure whether it provided that info. I did notice that it measures amp hours in and out. Also somehow indicates battery % charged, but I don't imagine that's particularly accurate.

Well I can't be certain, but I think its pretty accurate - at least better than trying to judge from voltage (or at least more convenient). One has to program it with the type and capacity of the battery bank, then it tracks usage and charging to calculate the percent full. The only thing I think might be more accurate is to test the battery with a hydrometer, following the requirements to fully charge it and remove the surface charge first. At any rate, if the TriMetric is properly installed and says that 30 amps are going into the battery.. I would take that figure to the (battery) bank. I use mine frequently to not only see how much charging current there is (esp. from solar panels), but more often to see how much current various loads pull. And in that regard it indicates very close to what I expect.

[Joe & Cherie]

Originally Posted by gordon2

He has answered this question (and here also). He has a TriMetric battery monitor. It uses a shunt on the negative side (first thing off the battery) and it measures the current going or coming from the battery (through the shunt). I have the same set up. More info at home - Bogart Engineering

Exactly! It reads +\- amps at the battery. On boost mode it’s at 29.5 but normal mode is 13ish if remember right. I cut the old fuse holder out so no more testing till I get a new one!

I agree the charge wizard is automatic. Upsizing the run from converter to switch to battery will be priority!

[Joe & Cherie]

Yes the trimetric I set for 220ah. My batteries are 225 and it only went in increments of 10 lol. So yes it measures usesge in/out. So after running fridge and volts were 12.2 my % was 61% full. After shutting fridge off and it sitting all day volts went to 12.3 and % stays at 61%. I agree it’s an accurate reading on usage %. You can also reset the % to 100 after charging but it normally stops at 100 or 102 max. I really like the meter s lot! I used the smaller shunt to get accurate readings to 0.01 amps instead of 0.1. It’s nice to see what each appliance draws.

I think we are definitely on the right track here if replacing the line and fuse to 40a/8ga! I bet problem solved!

[Civilguy]

Steve had an interesting point concerning making sure that the fuse's spade connector is actually inserted into the metal female terminal between the ears, and not just wedged between the terminal and the plastic jacket.

http://www.fiberglassrv.com/forums/f...tml#post711950

Maybe if you quit using this thing as a supplemental "heater", you can cut down on the current draw.

[Raz]

..............The meter is now showing 13.2 V charging and 29.5 A charging. This is on boost mode. It surprises me that the volts are not at 14.4 per the booklet......

Loading. The more current you draw, the lower the source voltage. When you start your car with the lights on, the lights dim. The high current demand of the starter lowers the battery voltage and dims the lights. Nothing wrong here. I would expect the voltage to rise to a maximum (14.4?) and the current to drop as the battery charges.