Renogy blown inline 10a fuse - what happened ?

[st1650]

Total newbie here, I bought the Renogy 4x 100w kit with 40a MPPT kit for RV before doing actual proper research, wasn't aware how bad these products are.

I had the local RV shop do the install, they set it up to code so I feel like it was installed properly, they installed the 150 aH lifepo battery inside, along with my 2500w pure sin inverter, put in the breaker, etc.

For a week it worked perfectly. The trailer is parked in the sun and was keeping the battery fully charged to 14.5V

Then we had a couple days of rain, then more sun and I came back to the trailer today so do some test and the battery was dead.

I trickled charged the battery back up to 13v so the MPPT controller would come back to life but it wasn't taking a charge from the panels.

I started testing a bunch of different things and then went on the roof, I saw that the positive lead has a MC4 10amp fuse so I took it off and saw that the fuse was dead. I swapped it with another 10A MC4 fused connector that I have for my portable 100w renogy and everything came back to life.

I also checked the MPPT controller setting for LI battery and saw that the default settings are not good, so I updated them per the guide on one of the thread here.

Now the question is, what could have blown this 10a fuse ? Should I try a 30amp inline fuse instead ? It never got above 25C so I doubt it was the heat.

 

[st1650]

This is roughly how its setup but with 4 panels instead of 4, the fuse is installed after the Y branch connectors

 

[efficientPV]

4x 100w kit with 40a MPPT kit for RV ..... Doesn't say much. Are the panels in series, parallel or combination. 100W panels won't put out much more than 5A. Many RV are in parallel because of potential shading. We often hire professionals who don't really know more.

 

[st1650]

parallel configuration - pretty much like this one:

 

[42OhmsPA]

parallel configuration - pretty much like this one:

More than likely exceeding 10A and the fuse is doing its job. We'd need panel specs to be certain but I'd bet money on it.

 

[st1650]

More than likely exceeding 10A and the fuse is doing its job. We'd need panel specs to be certain but I'd bet money on it.

Hopefully the 30a fuse fixes the issue, just weird that they would include such a low fuse with the kit when they include 2x15A fuse on their 2x200W kits.

 

[42OhmsPA]

Hopefully the 30a fuse fixes the issue, just weird that they would include such a low fuse with the kit when they include 2x15A fuse on their 2x200W kits.

Panel amperage rating x1.25 should be a good fit.

 

[efficientPV]

In such a small system that fuse does absolutely nothing. When there are more than two panels in parallel, each panel should be fused. Why do you even have a MPPT controller if you are going to operate all panels in parallel. For best performance put two panels in series and then those two strings in parallel. That install is goofy.

 

[mikefitz]

configuration - pretty much like this one:

Four 100 watt panels in parallel can deliver over 20 amps in ideal conditions. Reconfigure the panels, two in series , connected in parallel with the other two, also configured as a series pair. No fuse is needed for this configuration.
Your local RV shop should have used this method, and set up the charger correctly.

 

[LakeHouse]

Now the question is, what could have blown this 10a fuse ? Should I try a 30amp inline fuse instead ?

No, absolutely not. The solution to "I blew a fuse" isn't "Install higher rated fuse". That's a recipe for a fire. Fuses protect wiring and components from excessive current, which leads to heat, which leads to fires. Your panels with have a sticker on the back that lists a 'max series fuse rating'. Don't put in a higher rated fuse than that if you're going to parallel more than two panels or strings of panels.

Now, on to what happened... I'm speculating a little based on what you've written, but: In your description you say that all four panels were connected in parallel, and the fuse was installed after the Y branch connector. This is an incorrect installation. Each panel needs a fuse (with four in parallel, anyway), but that fuse needs to be in the circuit that only contains that particular panel, i.e., on the panel side of the Y connector. So the order should be panel -> fuse -> Y connector. The 10A panel fuses go here:


If they're downstream of those Y connectors, you're adding up current and on a sunny day when your battery isn't full you should expect to produce close to the rated current which is likely going to be something like 5A per panel, so the combined is 5A + 5A + 5A + 5A = 20A. 20A should blow a 10A fuse.

The solution suggested by others of switching to 2s2p is fine, and would eliminate the need for any fuses on the PV side, but does come with the downside with an RV installation that one shaded panel drags down production from it's series partner as well. You can certainly stick with the four in parallel installation, if it's done correctly.

 

[robbob2112]

What size are the wires between the panels and the MPPT - this dictates the max size fuse - not that you should go there. If the wires are different sizes connected together you have to use the fuse that matches the smallest wire. I would be willing to bet the wires from the panels are 14awg and no bets on the rest of them.

Also the Y connectors you are using have a max current rating you can't exceed.

Simplest fix is provides above as 2p2s

14awg = 15a
12awg = 20a
10awg = 30a