DC-DC charger fuse question

[AJMike]

Originally Posted by Winterbagoal

Can you remove/bypass the DC to DC charger, and see if that solves the fuse problem? Or was the blown fuse a one off?

I don't know any easy way to do that. The charger is wired in-line between the alternator and the batteries and aside from the buttons that allows a connection from the starter battery to the house batteries I don't know any other way to get power to the house batteries.

There is an ON/OFF switch that removes the charger completely from the alternator to the batteries, but that also removes the only connection between the two. The only way I could see to do that would be to wire a bypass between the charger input and output connections.

As to whether the blown fuse was a "one off", I have no way of knowing at this point. We have a scheduled trip to the New Mexico mountains in about 10 days and I can try then to see what happens when I extend and retract the slide. If the fuse does not blow, then perhaps it was a "one off". If it does, then the problem still exists.

[jipper]

I have a 2019 Navion 24j and the slide circuit has a 30 amp breaker in the passenger seat house panel. I would think that yours would also be protected with either a breaker or fuse. If that breaker is smaller and it did not pop, the issue would be elsewhere.

[orangeminnie]

How long of a run and what wire size to the input of the DC-to-DC?
If the voltage at the input of the charger drops a lot, the current will soar to make up for it. I suggest a #2 wire, or even larger, to minimize voltage drop.

[AJMike]

Originally Posted by jipper

I have a 2019 Navion 24j and the slide circuit has a 30 amp breaker in the passenger seat house panel. I would think that yours would also be protected with either a breaker or fuse. If that breaker is smaller and it did not pop, the issue would be elsewhere.

That is interesting. I assume that there is a line from the alternator to the batteries and then another line from the batteries to the slide motor. Do you know which line that fuse is on?

Of course what has happened with our fuse is that the line from the alternator to the batteries was split and the DC-DC charger was inserted. The fuse that blew was between the alternator and the DC-DC charger and the slide motor still worked because that was powered by the batteries. I never even knew that the fuse blew until I noticed the lack of input to the batteries when we left the next morning.

[AJMike]

Originally Posted by orangeminnie

How long of a run and what wire size to the input of the DC-to-DC?
If the voltage at the input of the charger drops a lot, the current will soar to make up for it. I suggest a #2 wire, or even larger, to minimize voltage drop.

Yes, and I had not thought about a voltage drop. Ohm's Law would require an increase in current to compensate for a drop in voltage so that is a very interesting idea. Thank you.

I did not do the work myself so I am not sure about the wire gauge, but I did look to see what was done and the new wiring looks very substantial. When I spoke with the installer he told me that he used the recommended gauge as documented in the installation instructions.

The charger is basically within 3 or 4 feet of the batteries and I assume he inserted a post and tapped off of it to the charger and then ran a line from the charger to the batteries. The recommended gauge based on that length as specified in the manual is 6 AWG for the line from the alternator to the charger and 8 AWG for the line from the charger to the batteries. Both of those are smaller than the 2 AWG you mentioned but I saw no indication that there was any arcing or burning. Still, that is something that I need to look into.

I assume the installer knew what had to be done since he was one of those recommended by Battle Born and the installation he did appeared to have been a first class job when I looked at the work. Still I did not measure the wire gauge or look at the print on the wire insulation. I will do that before we leave for our next trip.

Thanks for the idea.

UPDATE:

I was reading through the charger manual and decided that it was worth copying some of the information and attaching it to this post. What struck me were the notices at the bottom of the table which I had not noticed before (imagine - not noticing the notices ...)

https://www.dropbox.com/s/qno8j1cie5...Table.jpg?dl=0

[al1florida]

When you did your test run and the 60amp fuse blew, you wrote that charge current displayed on your battery monitor was about 40amp and part of that was from the solar panels and the remainder was from the charger.

Based on the above details it highly unlikely wire size would have anything to do with a 60amp fuse blowing.

Don't get me wrong, wire size is very important to efficient charging. Loosing 0.5V to 1.0V has a significant affect on how fast the batteries will charge. But blowing a 60amp fuse is not likely to be one of them.

[al1florida]

I don't know what your situation is, but what I would do at my first opportunity would be to go over to my RV and spend a couple of hours at the storage location or just driving around town and testing everything I can think of to either recreate the failure or set my mind at ease that hopefully this was a one time failure.

[AJMike]

Originally Posted by al1florida

When you did your test run and the 60amp fuse blew, you wrote that charge current displayed on your battery monitor was about 40amp and part of that was from the solar panels and the remainder was from the charger.

I think what I wrote was that when we were driving the battery monitor showed between 37-42 amps going to the battery, that being the combined output of the charger and the solar panels minus that consumed by the refrigerator.

When we put out the slide I was not watching the battery monitor since I was trying to make sure that the slide did not run into any of the foliage or trees surrounding us. Similarly when I retracted the slide I was not watching the BM for similar reasons. Remember, I did not know there was a problem until we started to drive off in the morning, and only then because there was no power going to the batteries. That will change on our next trip as I will make sure the Victron app is running and displaying on the phone when I extend the slide although it will only show the output from the charger, not the input.

Originally Posted by al1florida

Based on the above details it highly unlikely wire size would have anything to do with a 60amp fuse blowing.

Don't get me wrong, wire size is very important to efficient charging. Loosing 0.5V to 1.0V has a significant affect on how fast the batteries will charge. But blowing a 60amp fuse is not likely to be one of them.

I assume you mean to write "slide" and not "size" above.

I don't really know how the charger works internally but since the input is DC and the output is DC I assume that there is some kind of inverter to transform the DC to some form of AC for a transformer on the input side and a rectifier to transform the AC across the transformer back into DC. Thus there would have to be a slightly higher current on the input to make up for the boost in voltage from 13.6 to 14.4 (or so) and to compensate for the efficiency loss in the inverter, transformer and rectifier. Thus I would not expect the input current to be much more than 45-50 amps. 60 amps seems like a lot to me, but I am not sure how much of a current boost is needed for normal operation so I don't know how close to 60 amps the input might be without any extra load like the slide.

The installer suggested that the input fuse might just not have been seated properly or that 60 amps may be a bit low, considering the use of the slide and that I might want to try a 70 amp fuse. I have replaced the fuse and will see if that has the same issue. I am a bit reluctant to try a 70 amp fuse for obvious reasons.

[al1florida]

Originally Posted by AJMike

I think what I wrote was that when we were driving the battery monitor showed between 37-42 amps going to the battery, that being the combined output of the charger and the solar panels minus that consumed by the refrigerator.

When we put out the slide I was not watching the battery monitor since I was trying to make sure that the slide did not run into any of the foliage or trees surrounding us. Similarly when I retracted the slide I was not watching the BM for similar reasons. Remember, I did not know there was a problem until we started to drive off in the morning, and only then because there was no power going to the batteries. That will change on our next trip as I will make sure the Victron app is running and displaying on the phone when I extend the slide although it will only show the output from the charger, not the input.



I assume you mean to write "slide" and not "size" above.

I don't really know how the charger works internally but since the input is DC and the output is DC I assume that there is some kind of inverter to transform the DC to some form of AC for a transformer on the input side and a rectifier to transform the AC across the transformer back into DC. Thus there would have to be a slightly higher current on the input to make up for the boost in voltage from 13.6 to 14.4 (or so) and to compensate for the efficiency loss in the inverter, transformer and rectifier. Thus I would not expect the input current to be much more than 45-50 amps. 60 amps seems like a lot to me, but I am not sure how much of a current boost is needed for normal operation so I don't know how close to 60 amps the input might be without any extra load like the slide.

The installer suggested that the input fuse might just not have been seated properly or that 60 amps may be a bit low, considering the use of the slide and that I might want to try a 70 amp fuse. I have replaced the fuse and will see if that has the same issue. I am a bit reluctant to try a 70 amp fuse for obvious reasons.

Originally Posted by al1florida View Post
Based on the above details it highly unlikely wire size would have anything to do with a 60amp fuse blowing.

Don't get me wrong, wire size is very important to efficient charging. Loosing 0.5V to 1.0V has a significant affect on how fast the batteries will charge. But blowing a 60amp fuse is not likely to be one of them.

I assume you mean to write "slide" and not "size" above.

When I wrote "wire size" I was talking about the size of the wire from the alternator to the charger and also the size of the wire from the charger to the house batteries. This was meant to reference the possible extra current pulled by the charger if the wire size was to small. Unless the installer put in 14 or 16 AWG wire (extremely unlikely that he would) just having 10 AWG would have only caused the charger to pull a few extra amps at the max 40 amp output, but not 20-30 additional amps needed to blow the fuse just because of #10 wire. I base this on the relatively short wire runs. If we were talking about 30-50 feet of #10 wire that could be different.

I could be wrong here, but I doubt your slide motor pulls more than 10-15 amps and that likely would be at startup and the motor load up when the slide is all the way in or out. I would expect the slide motor not be a really powerful motor, but one that runs at somewhat high RPM and then is geared down to provide the torque to move the slide.

I am in total agreement with you that I would be reluctant to install a 70amp fuse in place of the 60amp fuse.

I have to go back to the fact that the DC to DC charger is rated at 40 amps output. For the charger to pull more than 60 amps from the alternator would mean to me that something is wrong with the charger.

Keep in mind that the alternator is not likely to be putting out really low voltage, say around 11V to 11.5V, unless something was wrong. Also there is a backup power source to feed the charger. That is the engine battery. Even if the alternator had very low output the battery would still be providing 12.6V unless something ran it down. I bring up the low voltage from alternator because someone wrote about small wire size possibly causing the charger to pull enough current to blow the fuse.

All this is to say: "I can't see that there is much of a chance that the slide out has anything to do with the blown fuse." A fuse not seated, or a defective charger is much more likely. Or perhaps if the wire connections are not tight for the fuse, or the wire connections at the charger or at the chassis battery/alternator end are not tight.

[AJMike]

There were so many responses to my original post about the blown fuse that I thought I should update the thread. Everyone tried to be helpful and I wanted to let those interested know what happened on our latest trip.

We went to the New Mexico mountains to a mineral water campground. This is the place that I upgraded our batteries to Lithium for since it is in a canyon so there is sun for only a short time, it is heavily shaded by deciduous trees so you are lucky to get 60-90 minutes of direct sunlight for the solar and the campground does not allow any generator use. Our old wet cell batteries barely managed one night with our compressor refrigerator.

We were camping there for 2 nights and one other location for 1 night so I needed to extend the slide twice and retract it twice. This time I opened the Victron app on my phone so I could see the DC-DC charger output when opening and closing the slide and this time there was no blown fuse. The slide extended and retracted properly and the charger was still working after each operation, so perhaps the whole thing was just a bad or badly seated fuse.

I do not know for certain but I assume the slide motor uses a lot of power since I saw the charging voltage go from 40 amps down to 10 or so as the slide extended and, again, when it retracted. Given that I assume the slide motor uses something like 30 amps. I guess I should look at the size of the fuse to see what was expected but I did not think to do that until just now.

Thank you, everyone, who posted and tried to help.

[creativepart]

Originally Posted by AJMike

There were so many responses to my original post about the blown fuse that I thought I should update the thread.

Thanks! It's always good to circle back when you have more experience with an issue posted previously.

What about the batteries on the trip? How did you do? Or will you post a new thread on these details. I'm sure many of us want to know.

[AJMike]

Originally Posted by creativepart

Thanks! It's always good to circle back when you have more experience with an issue posted previously.

What about the batteries on the trip? How did you do? Or will you post a new thread on these details. I'm sure many of us want to know.

I did not know that anyone was interested, but I did keep some information. I will post what I have in a new thread.