Suspected Converter Problem

[LipschitzWrath]

Hey guys, back again. Hoping to gain some insight into an ongoing problem we've had this summer.

RV is a 2004 Fleetwood Terry Quantum AX6 365FLTS.

The rv came with a factory installed WFCO 8855 converter. First things first. If you go to their website, you will see 8855's are 220v input. This may be the case now but certainly wasn't in 2004. Mine is 120v input and I have photographic proof. Let's please not waste time disputing this.

WFCO says the 9855 would be pretty much an equivalent now.

Anyways, onto the issue. I am wondering if there may be a problem with my converter. The reason I suspect it is because of generally poor performance. In the off season, I replaced the single group 24 battery the PO was kind of enough to leave me with a pair of Group 31 AGM batteries, 105Ah apiece.

It seems that this charger takes forever to charge these things. We're talking like if the wall panel shows 2/3 full, I need to run the generator for like 8 hours to charge them.

On a recent trip, the Batts showed 1/3 full and even after running the generator for seriously like 12 hours, they only showed 2/3. This seems slow. I know the indicator system probably isn't scientific level accuracy, but reading at the Batts with a multimeter seems to corroborate.

Other weird issues:

Sometimes at night with our 12v lights on in the camper (LED retrofits), I can see the lights flickering.

I get substantially different readings on the multimeter if I probe the output terminals of the converter versus the batt terminals. This despite the cables connecting the two being less than 4 feet long. For example, I forced the converter into boost mode. When probing the outputs, I got like 14.46v. At the batt terminals, I get like 12.43v. This seems especially odd to me considering any other time I probe battery terminals with a charger connected and charging, it seems like I'm reading the charger output voltage.

Lastly, I pulled the troubleshooting chart from WFCO and followed all steps. According to the chart (link below), my converter is fine. But it certainly doesn't behave like it's fine. I know PD advertises that when in boost mode, it takes 2-3 hours to bring the battery bank to 90%. Admittedly, this WFCO isn't as good as a PD, but 12 hours? Really?

http://wfcoelectronics.com/wp-content/uploads/2015/11/New-Flow-Chart-for-WF-9800-Series.pdf

I have my eye on a PD9260, but I don't want to spend the money if there's something else wrong.

This past weekend the batteries were completely dead and we brought them home to charge on a more "conventional" charger. It took a long time, but it worked.

Any ideas? Are my batteries just THAT big? Or is there something else going on?

Tell me what you guys think.

[LipschitzWrath]

pianotuna wrote:
I believe you are over thinking this.

I love it when people tell me this. It usually means I have considered all the important pieces.

[pianotuna]

My main DC breaker is autoreset. I do have catastrophic failure fuse as well.

The only time the breaker has cycled is when I deliberately overloaded it to make sure it was working. Since I have changed my frequently used lights to led, I would no longer be able to deliberately cause it to overload.

Fuses and breakers are there to protect the wires. If an autoreset breaker is disconnecting often, then the wire size is not adequate to the load.

I do have circuit breakers on the dual charging paths from the engine to the battery bank. The OEM was a 60 amp fuse, which due to a large inverter failed 3 times in 8 months. I replaced the fuse with a 50 amp autoreset, and chose to do the same with the auxiliary charging path. I do have manual control over the relays that do the connecting.

I believe you are over thinking this.

LipschitzWrath wrote:
Another question. Would it be advisable to go with Type I (cycling) or Type II (modified reset) circuit breakers in this application. My inclination is to say Type II, but I thought I'd ask.

Seems like the breaker constantly cycling on and off (Type I) would be a bad idea.

[pianotuna]

Hi,

There are reverse polarity fuses in most converters. That offers protection from a short. DAMHIK

LipschitzWrath wrote:

The {old} converter outlet wire quickly disappeard behind a wall. I'm presuming that this wire also runs to the DC panel. There is no visible circuit protection on this wire. I don't see anything at the DC panel either. This leads me to believe this wire is not protected at all (factory setup). Thus, when you are powering your DC off the converter, the feed to the DC panel has no overcurrent protection. When running off the battery, you do.

Here's is the electrical path when running off converter:

Converter output --> DC Panel --> Circuit Breaker --> Battery bank

When running off battery:

Battery bank --> circuit breaker --> DC panel (conv output wire would also be energized, but irrelevant here)

The cabling upgrades I made did not modify this. BFL is spot on - before AND after my wiring upgrades, there is no circuit protection to the DC panel when running off the converter.

I intend to fix this.

This all assumes there is no hidden breaker or fuse stashed somewhere on the converter output that I have yet to find.

[MEXICOWANDERER]

Using a 5-amp fast acting fuse versus a 5 amp circuit breaker (modified reset) can make the difference between changing toasted FETs or having the fire department roll up.

Large surge items need to be analyzed in the AC inrush department before settling on a breaker or fuse.

[BFL13]

LipschitzWrath wrote:
Another question. Would it be advisable to go with Type I (cycling) or Type II (modified reset) circuit breakers in this application. My inclination is to say Type II, but I thought I'd ask.

Seems like the breaker constantly cycling on and off (Type I) would be a bad idea.

I don't know for sure, but some on here have argued against CBs and for fuses for some jobs. Also there are fast and slow ones. That fuses link has some info on that-- scroll farther down.

If it is a quick surge thing only, a resetting CB would be a blessing, but for a "real" over -amp event an actual fuse would be better. Some fuses apparently will still let it through even after they blow if the amps are that high. Others here will have to help with that topic.

[LipschitzWrath]

Another question. Would it be advisable to go with Type I (cycling) or Type II (modified reset) circuit breakers in this application. My inclination is to say Type II, but I thought I'd ask.

Seems like the breaker constantly cycling on and off (Type I) would be a bad idea.

[BFL13]

Another good link that explains everything

http://www1.cooperbussmann.com/pdf/1b416a65-f5ac-4730-ab77-9e2faa147945.pdf

[LipschitzWrath]

BFL13 wrote:
You don't need a fuse on the PV to controller line but it is handy to have some sort of switch for disconnecting that line before you disconnect the controller-battery line for any reason. Some guys use a fuse there so they can just pull it as their on/off switch.

Excellent point. I "know a guy" that had energized panels connected to the controller when there was no battery connection. This caused a malfunction within his controller whereby it would show 100W+ output in pitch black. There's a thread on that somewhere. 🙂

[LipschitzWrath]

pianotuna wrote:
There likely is an automatic circuit breaker in the positive feed near the battery bank.

Solar controllers are often wired directly to the battery bank, hence the need for a fuse near the battery bank. I tend to class these as catastrophic failure devices, so a fuse is "faster" protection than a breaker.

There is a breaker that the battery is connected to on one post, and the DC panel is connected to on the other post. This would provide protection when running off battery power.

The {old} converter outlet wire quickly disappeard behind a wall. I'm presuming that this wire also runs to the DC panel. There is no visible circuit protection on this wire. I don't see anything at the DC panel either. This leads me to believe this wire is not protected at all (factory setup). Thus, when you are powering your DC off the converter, the feed to the DC panel has no overcurrent protection. When running off the battery, you do.

Here's is the electrical path when running off converter:

Converter output --> DC Panel --> Circuit Breaker --> Battery bank

When running off battery:

Battery bank --> circuit breaker --> DC panel (conv output wire would also be energized, but irrelevant here)

The cabling upgrades I made did not modify this. BFL is spot on - before AND after my wiring upgrades, there is no circuit protection to the DC panel when running off the converter.

I intend to fix this.

This all assumes there is no hidden breaker or fuse stashed somewhere on the converter output that I have yet to find.

[BFL13]

You don't need a fuse on the PV to controller line but it is handy to have some sort of switch for disconnecting that line before you disconnect the controller-battery line for any reason. Some guys use a fuse there so they can just pull it as their on/off switch.

[LipschitzWrath]

BFL13 wrote:
I found this a great help wrt fusing. See the diagrams for how each wire gets its own size fuse etc when using buss bars.

http://www.bcae1.com/fuses.htm

You can think of your "junction" collection points as being buss bars for this purpose. Also note the idea of the single fat wire out one side carries the total amps of the branch wires. That also applies to the neg wires. The shunt will need that--collection of thin wires at one end, and a fat wire (two in your case) out the other end to the battery.

The solar controller's pos wire to battery should have a fuse on it already being a kit? Anyway, same thing-- fuse for its own ampacity as a "branch".

Your idea to make a drawing of your set- up's wiring is a good one. You can then see better what is going on for "branches" and all that

Good link. Truth be told, I guess I already knew that from my residential wiring experience with the NEC, but I guess I wasn't making the connection that it should also apply to low-voltage DC wiring. Said another way, it may be a code requirement when you're wiring a house, but it's just good practice on any wiring project.

That link still seems to support that I could do it either way. Running two #8's off the same breaker would be acceptable, so long as the breaker is sized for a single #8. This would be analagous to wire segments B & C in his example. If either wire shorted, the breaker would open the circuit before becoming overloaded.

As for the solar system, the kit I bought was a Renogy 200W kit. It did not come with any sort of circuit protection for either the battery cables or the cables from PV to controller. Odd, I know. What makes it even more odd is that there is a clear reference in the owner's manual (that I skipped over) to install circuit protection on both of those cable runs.

Their recommendation is the full capability for the controller on the battery cables - 30A in my case. For PV-controller, the example they use is for a 200W array, and they suggest an 18A fuse/breaker. I'm calling it 20.

[pianotuna]

There likely is an automatic circuit breaker in the positive feed near the battery bank.

Solar controllers are often wired directly to the battery bank, hence the need for a fuse near the battery bank. I tend to class these as catastrophic failure devices, so a fuse is "faster" protection than a breaker.

LipschitzWrath wrote:
A couple things to add.

My second method above (2x 40A breakers) makes no sense, at least if you're powering off the converter. The converter breaker is going to open before you reach the ampacity required to open either feed breaker, unless the battery is somehow "supplementing" the DC load.

[BFL13]

I found this a great help wrt fusing. See the diagrams for how each wire gets its own size fuse etc when using buss bars.

http://www.bcae1.com/fuses.htm

You can think of your "junction" collection points as being buss bars for this purpose. Also note the idea of the single fat wire out one side carries the total amps of the branch wires. That also applies to the neg wires. The shunt will need that--collection of thin wires at one end, and a fat wire (two in your case) out the other end to the battery.

The solar controller's pos wire to battery should have a fuse on it already being a kit? Anyway, same thing-- fuse for its own ampacity as a "branch".

Your idea to make a drawing of your set- up's wiring is a good one. You can then see better what is going on for "branches" and all that

[LipschitzWrath]

A couple things to add.

My second method above (2x 40A breakers) makes no sense, at least if you're powering off the converter. The converter breaker is going to open before you reach the ampacity required to open either feed breaker, unless the battery is somehow "supplementing" the DC load.

Speaking of the converter breaker, I lied to you. I thought it was a 60A breaker, but upon closer inspection, it's a 50A. Hey, it was dark, okay? This is supported by the fact that the largest shortstop breaker Bussman manufactures is a 50A.

Based on this, would you recommend splitting the converter output across multiple breakers? This would allow more flexibility if I went to a larger converter later, but I'm not sure that will ever become a reality based on your comment that only one of my genny's won't be able to support much over a 60A converter.

Lastly, I was looking at some of the brackets and buss bars they have available for ganging together multiple shortstop breakers. I'm envisioning that I could set this up in a manner that would preclude the need for a positive buss bar and still have no more than two connections on any stud.

Eager to hear your thoughts...