30-amp fuse hot as a firecracker!

Here's my problem: I have 2 Trojan T-105 6-volt batteries wired in series. When I hook up to AC power, the fuse gets extremely hot - so hot that the solder oozes from the ends of the fuse. But only when I hook to 120v AC. I called TrailManor, and they sent me a new converter (under warranty). I swapped out the converter with the new one. I'm still having the same problem. I'm going to run down the positive wire and make sure it's not shorting against anything. When disconnected from outside current, the fuse does not get hot. As soon as I hook up to outside power, the fuse gets hot. I had to replace the fuse holder as it got so hot that it melted the fuse holder. Instead of the glass, I went with the plastic fuses (30-amp). Still getting hot. I took a reading across the poles of the battery. When hooked up to outside power, it reads 12.93 volts. When disconnected from outside power, it reads 11.7 and I'm confused. I'm not sure if it's a short, I'm not sure if it's a converter issue. Something is making the fuse very hot when hooked up to outside power.

Does anybody have a clue as to what my next move should be?

[Caver]

Originally Posted by mytlamb

Here's my problem: I have 2 Trojan T-105 6-volt batteries wired in series. When I hook up to AC power, the fuse gets extremely hot - so hot that the solder oozes from the ends of the fuse. But only when I hook to 120v AC. I called TrailManor, and they sent me a new converter (under warranty). I swapped out the converter with the new one. I'm still having the same problem. I'm going to run down the positive wire and make sure it's not shorting against anything. When disconnected from outside current, the fuse does not get hot. As soon as I hook up to outside power, the fuse gets hot. I had to replace the fuse holder as it got so hot that it melted the fuse holder. Instead of the glass, I went with the plastic fuses (30-amp). Still getting hot. I took a reading across the poles of the battery. When hooked up to outside power, it reads 12.93 volts. When disconnected from outside power, it reads 11.7 and I'm confused. I'm not sure if it's a short, I'm not sure if it's a converter issue. Something is making the fuse very hot when hooked up to outside power.

Does anybody have a clue as to what my next move should be?

It's possible that you have a shorted cell in one of your 6 volt batteries. Check the voltage across each battery without the AC connected. I would not leave it connected to AC until you resolve this problem.

If there is a bad cell that batery will read about two volts lower than the good battery.

Good luck with your troubleshooting. Ray

Thanks for the input. I did that first off before anything else.Both batteries checked out O.K. In series 11.70volts and separately 5.85volts low but no dead cells. Thanks alot for your input.

><>Danny<><

Hey Danny,

Your voltage readings while hooked up to AC (12.93vdc) and without hookup (11.7vdc) seem good to me as this would reflect the converter in a normal charging state. I do not think the converter is the problem -- particularly since it has recently been swapped out.

However, the high heat is very worrisome from both a safety standpoint as well as any downstream component damage to your wiring harness. There is no way you should be building up that kind of heat.and this would seem to reflect a high constant current load that is somewhat less than the amount necessary to open the 30A fuse. (In other words not a dead short.) I would suggest opening all the circuits at the power center and then systematically closing the individiual circuits at the power center one at a time to see if you can isolate the problem to a particular circuit.

In fact I would start with the AC attached and all circuits open to confirm that there is no current draw (therefore no heat).

If available, using an ammeter would be helpful but not essential.

I will be working on my TM the next couple of days so I could take some readings on my unit for comparrison sake. I would most DEFINITELY get this taken care of ASAP.

God luck,

Steve

Hi again,

Another thought would be to disconnect your current battery and substitute a car battery to confirm whether it is the battery or one of the AC circuits described above.

Steve

Thank you Steve,
Very good idea and I will give it a try. I also have some other things to try.

><>Danny<><

[Bill]

Mytlamb -

Your voltage of 11.7 VDC is way too low. It represents a fully discharged battery, though of course without any further info, I have no idea why it is discharged. It sounds like your converter is trying VIGOROUSLY to charge this dead battery, and you can't fault the converter for this.

Caver's suggestion of a shorted cell sounds good. When you measured the voltage, did you measure it while there was a load on the battery? This may be the only way that the problem shows up as a voltage measurement. Disconnect shore power, and turn on a bunch of interior light - then make the measurement while they are on. Wait five minutes, and make it again. Are the battery voltages still equal?

Unfortunately, I don't think that turning off individual circuits will help you. The problem as described is in the battery, not the circuits. If there were a bad circuit, the converter would try hard to power that circuit, and might blow the fuse associated with that circuit - but the excess current wouldn't pass through the battery fuse.

Finally, it was a good idea to replace the original glass cartridge fuseholder with an ATC automotive fuseholder. The glass fuse holders are famous for overheating and melting the plastic, even in the absence of a problem. An ATC fuseholder should not overheat.

Let us know what you find.

Bill

Hey Bill,
Sorry I have'nt had a chance to reply before now. Chris and I have been camping.Anyway, you are absolutely right the battery was desperately low I gave it a full charge and so far so good. Have'nt had a "HOT FUSE EPISODE" since. Where I blew it was thinking that the converter kept the battery fully charged at all times.I will now put a charger on it and be sure of a full charge before departure. I'm going to go with 8 Guage wire from converter to battery soon. It's Doable and I will feel better about it not heating up.

Thanks alot Everybody for your input. It's folks like you that make this website "GOLDEN". <><Danny><>