Charge controller reading panels only when hooked directly to panel, not extension cables

[Cwing]

Hello!

Fairly new to this stuff. I am hooking up a Renogy setup to my truck camper. my gear is the following:

-100W Renogy flex panel
-50A Renogy DCDC MPPT charge controller
-100AH LiFePo Battery
- 8 Gage solar panel extension cables (https://www.amazon.com/dp/B09GV5TVY1?ref=ppx_yo2ov_dt_b_product_details&th=1)
- 4 gage wire running to Battery

Problem: When hooking my panel to my extension cables that take my panel up to the top of my camper, my charge controller does not read a signal. It does however read signal +/- 75W charge to my battery when hooking the panel directly to my charge controller (Skipping my extension lines and thus not allowing me to mount my panel on top of my camper).

I have tested everything I could think of with exception of just swapping out my extension cables.

-I have continuity on both my red and black extension cables meaning connections appear sound
-Multimeter reads POSITIVE 20V when reading AT THE END of my extension cables when panel is hooked to them, so my polarity seems to be correct and continuity is verified
-Tried on my Renogy Rover charge controller, same outcome
-Tried with different solar panel, same outcome

My extension cables are 8 Gage prebuilt cables purchased off amazon and the entire remaining cable setup uses 4 Gage. I assume it is my cables that are to blame? Voltage drop? voodoo magic curse??

What is wrong here?? I have tried everything I can think to do. Is there something I am missing here? Do I need higher quality extension cables?

I appreciate any advice you can provide. Feeling pretty dumb right now.

 

[littleharbor2]

Possibly the extension cables MC-4 connectors have contacts that are not making actual contact with other MC-4 connectors contacts?

 

[efficientPV]

Will the cable plug inti itself? Possibly the connectors are reversed on one end and getting reverse volts.

 

[Supervstech]

What is the wiring in your picture?
It appears you have the PV wiring connected to a bussbar... that is not correct.
PV should connect to a charge controller only...

 

[Mattb4]

Not familiar with your SCC but I find it strange that it does not have a PV negative instead it has a Alt (+) that you seem to have connected back to a common DC bus. This does not appear to be correct to me. Check your manual.

 

[timselectric]

Definitely odd to not have a PV (-) terminal.
I assume that the alt (+) is for a starting battery?
It appears to just be running to a fuse, for future use.

 

[Rednecktek]

Definitely odd to not have a PV (-) terminal.
I assume that the alt (+) is for a starting battery?
It appears to just be running to a fuse, for future use.

Will's review way back when showed that the DCDC uses a common ground so PV- and DC- are the same port/bolt. He's got that all going to a bus bar so that should be fine.

Although the Alternator+ doesn't seem to go anywhere after the fuse so what's it getting power from?

I'd replace the MC4 heads on the extension cables, I've got one that I'm re-heading because it would show phantom voltage from the panels/source with the meter but the voltage drop goes to 1.2v when it's trying to go under load. If I jimmy the wire it seats in better and works fine until the next time I wiggle/pull on it. My new connectors should be here Friday. Try shoving the MC4 connectors together at each joint holding the wire instead of the housing and see if it makes a difference. You could also do an ampacity test at the end of the cable to see if that's the culprit.

 

[timselectric]

Will's review way back when showed that the DCDC uses a common ground so PV- and DC- are the same port/bolt. He's got that all going to a bus bar so that should be fine.

Yes, I've seen this on a DC to DC charger. Just have never seen it on a solar charge controller.
But I agree that it shouldn't be a problem, since it appears to be designed that way.

Although the Alternator+ doesn't seem to go anywhere after the fuse so what's it getting power from?

Nowhere, yet.
Maybe for future.

I'd replace the MC4 heads on the extension cables,

Yup
Not all MC4 connectors are the same. (Even though they are supposed to be) It's probably a compatibility issue.

 

[Rednecktek]

I think that's the Renogy DC-50 unit Will reviewed by the looks of it.

 

[jasonojordan]

Have you ohm'd out your extension wires to make sure there isn't a issue with the cable itself?

 

[Supervstech]

Interesting configuration for sure.

Will's review way back when showed that the DCDC uses a common ground so PV- and DC- are the same port/bolt. He's got that all going to a bus bar so that should be fine.

Although the Alternator+ doesn't seem to go anywhere after the fuse so what's it getting power from?

I'd replace the MC4 heads on the extension cables, I've got one that I'm re-heading because it would show phantom voltage from the panels/source with the meter but the voltage drop goes to 1.2v when it's trying to go under load. If I jimmy the wire it seats in better and works fine until the next time I wiggle/pull on it. My new connectors should be here Friday. Try shoving the MC4 connectors together at each joint holding the wire instead of the housing and see if it makes a difference. You could also do an ampacity test at the end of the cable to see if that's the culprit.

The issue most likely is between the #8 mc4's and the connections to the panels.
I would remove the mc4's from both, and connect together in a combiner box.

 

[Cwing]

Wow awesome! Thank you everyone! I think you are right in assuming it is the MC4 Connectors. I may try hard wiring them to weed out that issue. I just hope I can get the connection with the MC4s up top as they are the only waterproof connector I would imagine for that application. Addressing a couple of your comments.

-The common Neg Bus bar appears to be working correctly. Like I mentioned, when I skip the extension cables the SCC runs as expected.
-The red alternator cable that is connected to the 60A fuse is now connected to my starter battery and is working as expected. Thankful for that because its the only way I can charge my battery at the moment!