Solar MC4 connectors - needed? Why?

[bpounds]

I'm in the early planning stage of doing a solar install on our fiver. I see the MC4 connectors and combiners are commonly used, and I wonder why, and if there is a reason why I could not just solder and seal the conductors between panels, and even between the array and the leads down to the controller. It doesn't seem like a common thing to have to replace a panel. At least not common enough that you would need a quick disconnect. I understand the connectors also make it idiot proof as far as polarity, but so what?

The MC4 connectors are cheap enough, so that's not an issue, but it just seems like a lot of fooling around with pins and housings, for no benefit. I like soldered joints when practical.

Opinions?

[westend]

The MC4 wire and connectors will far outlast even an exterior rated extension cord. The connections are waterproof and UV resistant. IMO, there is no good reason to use anything but MC4 for solar installation.

FWIW, I like to solder and seal my connections, also. I have a dozen wires under the trailer that are all lead through conduit and boxes to their final termination on the tongue of the trailer. Their terminations at the brakes and lights are all soldered.

[bpounds]

time2roll wrote:
https://www.solarblvd.com/product-category/solar-panels-systems/24-volt-solar-panels/

This company is near you and I. Have you been to their warehouse?

[Almot]

Yes, 24V panels almost never come with free shipping, they are too bulky. But if you want to max your wattage up, this is the easiest way.

24V panels are popular in residential and commercial installs, a company will be happy to sell you a couple. Time your purchase with some trip through that area - this is what I did. Just one of many residential/commercial suppliers, a huge warehouse full of panels.

[beemerphile1]

Got my 100 watt panels from Home Depot for $89 each (now $99) and free shipping. Shipping is a killer at some places.

[Almot]

Bpounds, big panels from 180W and up are twice cheaper per watt than 100W panels and are very common today. 280W are often same size as 220W, 300W is slightly bigger. Solar Blvd is a good source.

Big panels are 24V nominal, this means you need to use MPPT controller, more expensive than PWM, but in the end $/watt cost of 600W system will be the less than 200W.

For sustainable living on solar you want at least 300W. Having more wattage won't hurt, because in rain and low overcast solar output drops several times.

[time2roll]

https://www.solarblvd.com/product-category/solar-panels-systems/24-volt-solar-panels/

[bpounds]

I was over simplifying, but space for 2 panels is what I have where there won't be shadow from A/C and roof vents. And 100w panels seems to be the most common and least expensive.

I see 175w panels, roughly 5' x 2.5'. Likely those would fit in the same space as the 100w with a nice bonus in output.

280w and even 260w panels don't seem to be common.

[Almot]

Except for some really tiny egg-shape 5-ers, there is no way you don't have enough space for 560W (at least). That would be 2*280W in series. With 40-45A MPPT controller. ~$700 total.

2*100W is a no-brainer, with PWM Grape 40 controller, $280-300 total including extension cable. For parallel wiring you will need a pair of MC4 Y-splitters

[bpounds]

Thanks for all the comments. I'll probably be moving pretty slow on this, but now I have the points to consider.

I was dreaming of an array of 4x100W panels while sitting at my desk. So thinking of 2 in series x 2 in parallel. But when I actually climbed up on the trailer and considered the space I have to mount them, I'm probably only going to fit 2x100W. Cutting an extension cord in half makes a lot of sense.

[Almot]

bpounds wrote:
I see the MC4 connectors and combiners are commonly used, and I wonder why, and if there is a reason why I could not just solder and seal the conductors between panels, and even between the array and the leads down to the controller. It doesn't seem like a common thing to have to replace a panel. At least not common enough that you would need a quick disconnect. I understand the connectors also make it idiot proof as far as polarity, but so what?

The MC4 connectors are cheap enough, so that's not an issue, but it just seems like a lot of fooling around with pins and housings, for no benefit.

Starting from the end... MC4 are not "cheap", but essentially free (to you). Panels of RV size come with MC4, 99% of them. So, the real question is - are there any benefits in removing them.

For most people there isn't any. Like Time2roll said, MC4 are plug and play. Works well for either series or parallel wiring. You would have to cut them off for junction box, IF you decide to have J-box. Unless you go for a big array made of 12V panels in parallel (a rare situation these days), you don't need a J-box.

Leads from panels to controller is a different matter. Most people use MC4 extension cable for convenience. You cut it in half, MC4 connect to MC4 on the panels, and bare ends go to controller. You could cut MC4 off and solder this lead to the panels, but there is usually reason.

[Tom_M1]

KD4UPL wrote:
If you modify the panel in any way, such as cutting off the connector, it will void the warranty. If you're not worried about that then go ahead. If you think you might want the warranty don't cut the wires or modify the junction boxes.

The pigtails were easily removed on my panels by unscrewing them from the terminals in the junction box. Just save a couple of pigtails and reattach if you think voiding the warranty could be a problem. Some junction boxes are sealed up, so removing the pigtails could be a problem.

[mike-s]

KD4UPL wrote:
If you modify the panel in any way, such as cutting off the connector, it will void the warranty. If you're not worried about that then go ahead. If you think you might want the warranty don't cut the wires or modify the junction boxes.

That's an awfully broad statement without knowing exactly which panels he intends to use. Because, it's not true in general.

[KD4UPL]

MC4 is the standard. Most panels are installed on buildings where there are 10s or even 100s of them. In those installations cutting and soldering would be way too complicated. If you modify the panel in any way, such as cutting off the connector, it will void the warranty. If you're not worried about that then go ahead. If you think you might want the warranty don't cut the wires or modify the junction boxes.

[time2roll]

MC4 makes it all plug and play. To pull wire to the controller get a pre-made MC4 extension cable and cut in half. MC4 ends on the panels, cut end on the controller. MC4 cable is always UV resistant.

Combiner-junction box just adds a fail point. MC4 is used on home installations and expected to last 30+ years in all conditions.

Otherwise no, you don't need MC4 if you really want to roll your own.

[bpounds]

Tom_M wrote:
I have 3 panels which had pigtails with MC4 connectors. I removed the pigtails and wired direct to the terminals in the junction boxes on the back of the panels. It's easy enough to get to the terminals if I need to remove a panel. Any connector will add a little resistance. The fewer connections the better.

Even better idea. I wasn't sure if those boxes opened easily. Probably voids the warranty, but that's okay.