MC4 Connectors SUCK for off-grid systems!!!

[garybeck]

It's been a few years since I installed a PV system. I'm old school. I've sold hundreds of PV systems, but almost all of them were in the early 90s. I'm used to seeing a nice junction box with knockouts on the back of a PV panel.


Recently I was asked to go to Haiti to install a PV system in a remote village that has no power. It would provide lighting and cellphone recharging for a small community. I jumped at the opportunity to help people in need.

I just got back. Everything went OK but I have to rant a little bit about MC4 connectors. THEY SUCK! I can see they would be nice if I had to string a bunch of panels together in series. But don't you think if a panel is 55 watts and 12 Volts that there's a good chance that the user would want to wire them in parallel?

not only are the fancy connectors on the end USELESS to me because the male-female paring is only set up for series connections, but the junction boxes are also useless. The MC4 wires are soldered in there with no way for me to remove them without a soldering iron. Anyone got a soldering iron at 5,000 feet up in the mountains of Haiti? And even if I could remove them there's no convenient way to bring in my own wire - no terminal strip -- all I can do is cut the ends off the MC4 wires and figure out some way to make it not look completely ugly. I ended up having to make some connections outside of conduit with splitbolts -- the only thing I had to get the job done, and it looked like ****.

don't they know that parallel connections require TWO wires coming in to each terminal?

xxxxxxxxxxxxxxx

someone should design a universal connector so you can make parallel and series connections with the same ends. But even then, you still need to bring two wires in to each terminal ON THE MODULE when you're making parallel connections, so we need a terminal strip. If you're going to put those useless MC4 things in there, at least make a convenient way for us to remove them and bring in our own wires.

Anything that is 100 watts or less and 12V nominal should not have MC4 connectors on it. Just give us a junction box, knockouts, and terminal blocks.

OK, I'm going to complain to the manufacturer now. Thanks for listening. Have a nice day.

[inetdog]

It's been a few years since I installed a PV system. I'm old school. I've sold hundreds of PV systems, but almost all of them were in the early 90s. I'm used to seeing a nice junction box with knockouts on the back of a PV panel.


Recently I was asked to go to Haiti to install a PV system in a remote village that has no power. It would provide lighting and cellphone recharging for a small community. I jumped at the opportunity to help people in need.

I just got back. Everything went OK but I have to rant a little bit about MC4 connectors. THEY SUCK! I can see they would be nice if I had to string a bunch of panels together in series. But don't you think if a panel is 55 watts and 12 Volts that there's a good chance that the user would want to wire them in parallel?

not only are the fancy connectors on the end USELESS to me because the male-female paring is only set up for series connections, but the junction boxes are also useless. The MC4 wires are soldered in there with no way for me to remove them without a soldering iron. Anyone got a soldering iron at 5,000 feet up in the mountains of Haiti? And even if I could remove them there's no convenient way to bring in my own wire - no terminal strip -- all I can do is cut the ends off the MC4 wires and figure out some way to make it not look completely ugly. I ended up having to make some connections outside of conduit with splitbolts -- the only thing I had to get the job done, and it looked like ****.

don't they know that parallel connections require TWO wires coming in to each terminal?

you're probably wondering what modules I was using:

http://www.siliconsolar.com/55-watt-solmaxx-solar-panel.html

note they are listed in their "off grid" section.

someone should design a universal connector so you can make parallel and series connections with the same ends. But even then, you still need to bring two wires in to each terminal ON THE MODULE when you're making parallel connections, so we need a terminal strip. If you're going to put those useless MC4 things in there, at least make a convenient way for us to remove them and bring in our own wires.

Anything that is 100 watts or less and 12V nominal should not have MC4 connectors on it. Just give us a junction box, knockouts, and terminal blocks.

OK, I'm going to complain to the manufacturer now. Thanks for listening. Have a nice day.

Rant duly noted and accepted!

I can see that it would have been more manageable if the manufacturer had made this obvious in their specs and you had been able to plan for it before going on site!

Except for cost, making up an elaborate wiring harness in advance with all of the MC4 connectors on it make the parallel array hookup would have looked better, but still been impossible to expand unless it was also designed for that. The cost of two MC4s on each terminal of the panel from the manufacturer would not make a lot of sense, and a terminal strip instead of soldering would make the panel assembly less reliable. Maybe an option from the manufacturer to mount a connector box with terminal strip instead of the MC4s? But then both versions might have to go through all of the approvals separately.

I don't see a good solution other then information.

PS: Apparently the cheapest way for most people to get assembled MC4 connectors to use for harnessing is to buy MC4 extension cables and cut them in half.

PPS:

Anything that is 100 watts or less and 12V nominal should not have MC4 connectors on it. Just give us a junction box, knockouts, and terminal blocks.

I'm sorry, that would just make too much sense.

[Naptown]

One of many adapters

http://www.aliexpress.com/product-fm-img/521472866-Free-shipping-by-Post-1-pair-of-MC4-Parallel-connector-Adapter-1M2F-2M1F-TUV-certification-wholesalers.html

[billvon]

I just got back. Everything went OK but I have to rant a little bit about MC4 connectors. THEY SUCK! I can see they would be nice if I had to string a bunch of panels together in series. But don't you think if a panel is 55 watts and 12 Volts that there's a good chance that the user would want to wire them in parallel?

Yes! Splitters, my good man, splitters.

[garybeck]

One of many adapters
http://www.aliexpress.com/product-fm...olesalers.html

thanks. that is exactly what I needed. too bad I didn't know they exist before I left. that's what I get for quitting my job at Real Goods 15 years ago. I'm still stuck in the solar stone age. Next time I'll get those.

[Szabie]

I am also having that problem and was thinking can I splice the cables and solder them the are 210w 47v panels and I'm a long way from the shop but have a soldering iron any help greatly appreciated

[Wy_White_Wolf]

I am also having that problem and was thinking can I splice the cables and solder them the are 210w 47v panels and I'm a long way from the shop but have a soldering iron any help greatly appreciated

Doing so will void the warrantee on the panels.

WWW

[bcroe]

For anything exposed to water, I use a couple methods. One is to install weatherproof connectors. Those could be automotive
grade or MC4s. Note that MC4s left unconnected too long can be corroded and may fail later or not even mate. Don't leave
panels sitting around with loose leads; plug them together.

My other method is to coat the splice with liquid tape, then immediately install some snug heat shrink over it. When the liquid
tape squeezes out both ends of the heat shrink, its fairly waterproof.

MC4 splitters might plug together, but remember the current capacity of them is limited. Maybe not so good for a low voltage
high current setup. The object here is to get a durable design together in an expedient manner. The warrantees may fall where
they may, they haven't been very useful in my life. Bruce Roe

[Sunking]

I am also having that problem and was thinking can I splice the cables and solder them the are 210w 47v panels and I'm a long way from the shop but have a soldering iron any help greatly appreciated

That would be foolish, there is no reason to parallel panels. You can solder providing you meet two NEC conditions.

1. Solder cannot be used to make the electrical connection.

2. Solder cannot be used to make the mechanical connection

[garybeck]

That would be foolish, there is no reason to parallel panels.

what do you mean there is no reason to parallel panels? i'm working on a 12V system that has a 12V inverter and 12V battery and 12V panels. unless i wire each module directly to the charge controller, I don't see a way around makng parallel connections.

[littleharbor]

MPPT controller, series wired panels. Combiner boxes, or Parallel branch connectors.

[garybeck]

MPPT controller, series wired panels. Combiner boxes, or Parallel branch connectors.

ok i should explain more.

there is already there an array of (6) 50-watt 12V panels (with no charge controller).
im adding a 2nd array of about 600 more watts. I don't want to install 12 more 50 watt panels. I can get 150 watt panels at a decent price there.

i think this is a rare situation where it makes sense to wire all the panels in parallel. there will be two sub-arrays, but they are both 12V and the arrays themselves are in parallel, meeting at the input of the single charge controller (90-amp midnite solar).

i don't think it would be a good idea to have these 50 watt panels and 150 watt panels in series. and I don't want two charge controllers. I have to keep this thing as simple as possible.

schematic.jpg

[Mike90250]

Unless it's already installed and you are adding to it, I don't believe the Midnight Classic 150 can charge a 12V bank from only 19V panels. I think it needs more overhead voltage. But i take that all back if you have a Classic and it's charging now.
Do the panels have a Vmp spec printed on them ?
50W:___
150W: ___

You might be better off using the 50w panels with their current controller, and wire the new 150's in series for 100V and let the Classic do it's MPPT magic downconversion

Also, with all the parallel panels, you really should use Combiner Boxes with fuses or breakers in them. Breakers will make troubleshooting easier.
ATC fuses and fuse holders often fail with the continuous power a solar system puts through them, their spring contacts are OK in a car, but not for long period high amp applications.

Before you wire all the parallel batteries up, study the smartguage article on parallel batteries, and wire them the best you can.

http://www.smartgauge.co.uk/batt_con.html

[littleharbor]

Bite the bullet and buy a cheap 30 amp PWM controller for the 50 watt panels and series wire all four of the 160 watt panels into the Midnite Solar controller.. THAT is how to keep this as simple as possible.

[garybeck]

Bite the bullet and buy a cheap 30 amp PWM controller for the 50 watt panels and series wire all four of the 160 watt panels into the Midnite Solar controller.. THAT is how to keep this as simple as possible.

But i take that all back if you have a Classic and it's charging now.
Do the panels have a Vmp spec printed on them ?
50W:___
150W: ___

thanks for your advice. to answer the questions...

-no i can't get any specs on the panels that are there already. they are in a very remote location, and they are bolted down with security bolts.

-when i originally installed the system I put a charge controller there. it has been removed.

-i might be able to get specs on the 160 watt panels I'm adding, but you should try communicating with people in Haiti and asking them to go to the store and take a picture of the label on the back of a panel. the bottom line is I'm not going to know for sure exactly what I have until I get there.

-i am wary of putting a PWM controller on one sub array and MPPT on the other. I think they will fight each other. as you know the battery voltage is affected by the charge rate. if one subarray decides to taper the charge, it will affect the system voltage and the other controller will react. I'm worried they will be in constant battle. that is why i wanted to wire these two sub arrays in parallel and get a high amperage controller to handle it all.

and now i'm running out of time to figure this out!