Power Converter Blowing Fuses

wandalust

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Joined
Feb 14, 2024
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5
I have a 2024 22BHE which has blown the 30A fuse leading to the battery bank numerous times. I wanted to share my experience in case anyone else is experiencing the same issue.

We've been using our trailer since we purchased it in November, 2023. Right away, I installed 3x 100ah LI batteries (and relocated to a massive unused space under the sink). Since doing so, I've blown countless 30a fuses (as well as 60a, but more on that later). The power converter installed is a WFCO WF-9855-AD, and there is a WFCO promotional sticker which claims it can detect the difference between lead acid and lithium batteries.

The WF-9855-AD is rated to charge at 14.6VDC @ 50A for a Lithium battery. My bank of 3 batteries is capable of soaking up 150A, so the 30A fuse between the converter and the battery bank is blowing anytime I try to charge up from even 10-15% depleted. When camping this is resulting in not being able to charge from the generator and a pretty uncomfortable night after quiet hours. I’ve even bypassed the fuse using jumper cables in order to get a charge.

It doesn't seem like too much to ask that the stock wiring be able to handle the load placed on it by the stock power converter.

I attempted to correct this by upgrading the wiring to the battery bank with 6g copper and a 60A fuse (based on the spec sticker on the WF-9855-AD stating it's max output was 55A. However, my first field test of this configuration immediately blew a fuse.

It wasn't until I purchased a loop multimeter to test the actual amperage that I learned that the converter spikes its output to ~68A immediately upon activation, blowing my 60A fuse. I'm in for another wiring upgrade to get this all working but I’m very close to closing this issue up.

Has anyone else run into this issue? It doesn’t seem like the kind of problem that would be limited to this model.
 
The stock wiring CAN handle the load of the stock converter with a single lead acid battery. Since you upgraded the battery bank significantly, you need to upgrade the wire and breaker.
 
I’ve certainly learned that lesson. It just doesn’t…meet my expectations. The unit comes pre-wired for an inverter, because the designers were thoughtful and anticipated that a bunch of people would install one. The unit came pre-wired to handle several additional solar panels, in anticipation of those upgrades. I think it fits the same way of thinking to be prepared for owners to have more than one led acid battery as well and not need to pull wires to do so.

At any rate, this post was more about sharing my lessons (not to complain) so people can skip to a solution that works. Your reply is a good reminder that the “just enough” design upon delivery is more the norm and the “pre-wired for all your future needs” is the exception.
 
I have a DIY LiFePO battery that I built from four 302AH cells, so basically the same battery capacity that you have.....close enough to call them the same rating. The max charge current my battery is capable of, according to the cell data sheet is 250 amps continuous. I have a charger that is very flexible as far as settings and what type of batteries it can charge. My charger is capable of a 43.xx amps of output and when it goes into bulk charge mode, it will output 42 to 43 amps. It has never once tried to output some outrageous amperage...ever. Had I wanted to spend more money than I did, I could have bought a charger (same brand, higher wattage version) that is a 1200 watt model and it would have a charging rate at around 75/76 amps. The fact that the output of your WFCO went up to 68 amps when it is supposed to be only 55 amps, tells me that the current limiting circuitry inside is either not functioning properly or the components are cheap and has a lot higher tolerance for error than it should......and that should be a concern for anyone.

As far as you continually blowing 30 amp fuses, I'm failing to understand why there would be a 30A fuse in a circuit that has a possibility of outputting 55 amps......I guess it was the OEM wire that came with the camper......was it 8ga?
 
Wow. A DIY battery! I’m impressed.

Yes, it came with an 8 gauge wire from the charger directly to the fuse panel. From there, a 30amp fuse leads to another 8 gauge wire run to the tongue for the batteries.

I don’t know what charging rate a lead acid battery can handle, but even if being slower, enough of them in parallel will blow that 30 amp fuse.
 
Wow. A DIY battery! I’m impressed.

Yes, it came with an 8 gauge wire from the charger directly to the fuse panel. From there, a 30amp fuse leads to another 8 gauge wire run to the tongue for the batteries.

I don’t know what charging rate a lead acid battery can handle, but even if being slower, enough of them in parallel will blow that 30 amp fuse.

It's a pretty well known fact that LFP batteries will take on HUGE charging currents as compared to the Flooded Lead Acid (FLA) type batteries. Of course, that "pretty well known fact" doesn't necessarily apply to everyone because not everyone is familiar with LFP, and many people are really surprised at the differences between the two battery types once they become familiar with both. What it boils down to is....forget everything you know/knew about FLA when you are dealing with LFP. Chemistries are obviously different, but so are charging rates, voltages, discharge levels, storage methods, etc. LFPs have a much lower internal resistance and are thus much more capable of accepting much larger charging currents. Therefore, it is imperative to have a charger, or in our case with RVs...a converter/charger which I usually just call a C/C, that is able to provide the amount of current that is feasible to your system, yet will not do something out of the ordinary.......like dumping out current at 68 amps from a 55 amp C/C. For most people, myself included, the C/C will be the limit or determining factor on how quickly or slowly that the LFP battery charges. As I stated earlier, my cells/battery have the ability to take on up to 250 amps of charging current. I found absolutely no need to utilize that capability in my situation. The cost of the charger, the wire/cable to support that, and the fact that I'm just not in that big of a hurry.......ever, drove my decision to buy what I bought as it serves my needs.

My trailer came with 6ga wiring in it for the battery charging and 12VDC supply to the 12V fuse panel and certainly that would have been sufficient for the 43 amps that my C/C puts out. The problem that I had though, is that part of the output voltage going to the battery was being dropped with bad connections along the way from the C/C to the battery......to the tune of .6 to .7 volts. So if I look at the actual numbers in my case, I have my C/C set to a maximum of 14.2 volts. If you deduct that voltage drop amount off of that number, now you are down to 13.5 volts actually getting to the battery. That number will simply NOT fully charge an LFP battery. LFP cells are considered to be fully charged at 3.45 volts. When you have four of them charged to that number, your battery voltage will be 13.8 volts. So as you can see, if the most that the battery ever gets is 13.5, there is no possible way to achieve a full State of Charge (SOC) on the battery.....even though the C/C is outputting 14.2 volts. Voltage drop is a real concern in many of our campers, but the problem is, a lot of people don't know about it and don't know how to correct it.

Again, in my case, that 6ga wire was replaced with 2ga cable (which has a lower internal resistance than 6ga does per foot), and all new crimp on connectors, a new battery disconnect switch (voltage drop across the old one), new high current terminal strips, etc. Anything along the path from the C/C to the battery that was dropping voltage along that path was replaced with something that would not cause issues. The result is that now I have about .1 volt of drop from end to end......and that will provide 14.1 volts to the battery which is obviously above the 13.8 volts needed to fully charge the battery.
 
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