Changing charge controllers

WaterWheel · April 2016

Currently I am running one PT-100 which since the rest of my system is all Conext the PT-100 can't report solar harvest or be programmed beyond the dip switches. I'm considering changing over to using two Conext 60 amp 150v charge controllers. Currently I'm running 4 strings of 4 panels each (158v) to the PT-100. I would need to add two more panels (becoming 18 panels total) and switch to 6 strings of 3 panels each to get the voltage lower. This is something I can reasonably do and the combiner box can handle 2 more breakers so all good there.

The sticking point is running an additional underground line into the house from the panels. Lot of work there not to mention additional boxes ect. Can I run all the panels in on my current two THNN 6 ga wires (plus 8 ga ground) and spit the wires using a wire block to the two charge controllers or do I have to run another underground line? The wires can handle the 44 amps from the rewired slightly enlarged array (44 amps at 119v).

Bottom line is do I have to run a separate underground line from the house to the panels?

Dave Angelini · April 2016

I think I would buy an xw mppt-80-600 and have a system that worked well as a system. I have run 7,000 watts of solar to this unit for my northern customers. They use a 100 amp breaker and will current limit arround 80+ amps when heat sink temp and a few other parameters tell it to.
Any of your existing wire will work and if you can't get advice here then become a client and I will tell you alot more than you will find searching.

WaterWheel · April 2016

While I haven't gone through a summer with the current system my old 490 watt system was over 430 watts often for hours at a time 4-5 months a year (538 watt peak once) so I get some fairly strong sun. I will soon be grid tying since even in the winter my batteries are fully charged most days by lunch and this time of year by 11 am.

Does the 80-600 go over 80 amps for long periods so I can harvest and sell back to the grid? I don't mind some clipping but I'm trying to maximize my sold power in an effort to justify the solar system cost.

BB. · April 2016

Question. The 80-600 is the solar charge controller. It will reliably send "needed" DC power to the battery bank. Does not directly control power flow to the grid. It just tries to keep the battery bank "happy".

It is the dc to ac hybrid inverter that safely and reliably sells power to the grid (and runs of grid when utility power has failed).

-Bill

WaterWheel · April 2016

My panels come in to a 60 amp breaker in the PDP, then to the PT-100 controller, then back to a 100 amp breaker in the PDP before hooking to the bottom of the 250 amp breaker Conext supplied with the PDP.       The battery Pos also hooks to the bottom of this 250 amp breaker.      The XW 6848 inverter and nothing else is fed from the top of this 250 amp breaker.      This is wired per the Conext schematic.       This unfortunately means that all power runs through the charge controller.      Without the charge controller you'd have unregulated DC voltage.

My conscern is that at 80 amp capacity of the 80-600 will clip (?) above about 3800 watts when the panels will probably regularly be putting out over 4100 watts and are capiable of over 4500 watts with cloud effect.    (16 Sunworld 280 watt panels).

Still, I may just take the easier route and accept some summer time losses and get a 80-600.       What do you think?

BB. · April 2016

The most I would put on an MPPT solar charge controller would be:

80 amps x 59 volts charging (48v bank) x 1/0.77 panel+controller derating = 6,169 watt array maximum (cost effective)

77% efficiency is a typical warm weather efficiency. MPPT controllers will safely limit max current, and reduce current if controller gets hot.

Of course, run less than 100% current, controller runs cooler, electronics are happier.

-Bill

WaterWheel · April 2016

Ok, You guys have convinced me to run with the 80-600 and that it can handle the 4500 watt potential panel output. Expensive but ... so is life.

Back to the grounding others have brought up here. Currently my ground mount array, (metal frame in concrete) is only grounded from the metal panel rack back to the controller/inverter which is grounded to the house ground. The PT-100 instructions said a separate ground may trip it's GFI circuit so I did not separately ground the rack. My panels are black frame and ungrounded since I doubt the clamps penetrated the paint. Currently at 158v per string and with the higher voltage input requirements of the 80-600 soon to be 316v per string. Do I need to put ground straps on the panels and ground them to the frame? or do I want a separate ground stake for the frame and panels and see if it trips the GFI in the controller?

Panel rack frame is 80' from house ground.

mike95490 · April 2016

foolami said:

....... Does the 80-600 go over 80 amps for long periods so I can harvest and sell back to the grid? I don't mind some clipping but I'm trying to maximize my sold power in an effort to justify the solar system cost.

Whoa. If you are selling power to the grid, you should not be considering batteries, if you expect to save any $. The replacement expense of batteries will always run you into loosing $ territory.

WaterWheel · April 2016

mike95490 said:

foolami said:

....... Does the 80-600 go over 80 amps for long periods so I can harvest and sell back to the grid? I don't mind some clipping but I'm trying to maximize my sold power in an effort to justify the solar system cost.

Whoa. If you are selling power to the grid, you should not be considering batteries, if you expect to save any $. The replacement expense of batteries will always run you into loosing $ territory.

We lose power here fairly often for 2+ days at a time (5 days straight two years ago) so a battery bank makes sense, maybe not financially but is somewhat justifiable. As I mentioned earlier in this thread I've been using my batteries the last 6 months and now want to back off the battery bank and tie into the grid because I'm making a lot more energy than I'm using 9 days out of 10.

new2PV · April 2016

If you use a few mppt 60 150's keep in mind that you will benefit of multiple aux contacts, so you will be able to use that extra power your wasting, for load diversion, ie electric water heater, heat pumps etc. However the input volts can't go over 140 volts or it will shut down, so you need to look at your panel voltage at 3 panels in a string, to see if its safe.

WaterWheel · April 2016

The Conext 80-600 is on order but this will require higher voltage since the 80-600 requires at least a 195v input I'll be rewiring the panels a bit to make 318v at the combiner box. I'm currently using the Midnight solar 300v DC surge protector and may need to change to the 600v model but the 300v model seems to have a lot of wiggle room ( MCOC > 423v ) so do you think I can stay with my current 300v surge protector of do I have to buy a 600v DC surge protector?

MNSPD-300-300 spec sheet http://www.midnitesolar.com/pdfs/spd_frontBack_display_web.pdf

new2PV · April 2016

I would contact midnite solar but the documentation states nominal voltage 300v max.

Dave Angelini · April 2016

Good advice! The exact clamping voltage needs to be known. If it starts conducting in the middle of the night I would think you would be OK. In the day, not a good thing!

WaterWheel · April 2016

Midnight solar says changes the SPD to a 600v.

new2PV · April 2016

Great you can sell me your old spd............

WaterWheel · April 2016

$500 and it's yours although it may be a week or 2 before I change it out.

Dave Angelini · April 2016

I think your price is 6 times what they sell for new. Buying a used surge protector never sounds like a great decision.

new2PV · April 2016

I think he made a typo. $50 seems reasonable.

WaterWheel · April 2016

Oops, I was thinking for the PT-100 for $500. I haven't even considered selling the 300v DC SPD although I guess I could.

new2PV · April 2016

What other plans would you have for the SPD? You can use the money towards the new one.

new2PV · May 2016

Guess the SPD is not for sale?

WaterWheel · May 2016

My brother is buying the old controller and 300v DC SPDs.

At this time I'm just trying to get the system back up and running. It seems that the breakers I was using were rated for 150v and I had the panels wired for 156v and it worked fine. But when I bumped the panel voltage up to 312v I suspect that I've partially burned one of the breakers. The new Conext 600-80 controller shows receiving 277v but at only .2 amps and is putting out .7 amps to the partially discharged batteries. The panels are all testing fine putting out about 4 amps each and all connections have been double checked. I spent an hour on the phone with Conext checking that all wiring is correct but one of the breakers is very rough, almost locked up. A local solar guy suggested that if the panels were passing good amperage then I may have just enough connection somewhere to pass the voltage but not enough connection to pass any real amperage. Long story short I've got some higher voltage breakers on order and am praying that will do the trick.

I had never considered that the old breakers weren't up to the higher voltage.

Dave Angelini · May 2016

Maybe you should change your screen name?

Don't use the breakers until you get a new Disco, much more important to charge your batteries!!!
Most people just use the Square D 600vdc Disco. You don't have three strings right?

new2PV · May 2016

Your now using a 300 volt breaker at 312 volts? I would go with a higher rated breaker.It could burn up eventually too.

Photowhit · May 2016

Listen to Dave,

Connect 2 strings with out breakers, perfectly legal and safe! Then trouble shoot your charge controller issues.

Dave Angelini · May 2016

Thanks Photowhit!
Be careful also! Look at those warnings on the -80-600V and how death can follow! Does yours have the pix of guy lying on the ground
Cover the array or disconnect the MC4's
Turn-off the 48V breaker

Photowhit · May 2016

Yes, I should have said safe for the system....

WaterWheel · May 2016

Dave,    Yep,    If I knew how to change my screen name I suspect I would although the current screenname has a long and historic past.    I was using the breakers in the combiner box at the rack and MNPV4HV on the house as outside disconnects.     The replacement breakers that I've ordered are din mounted 1000v 20amp fused unless you guys have a better idea.

PhotoWhit,    If I had any of the heavy butt connectors that can be used temporarly or permanently like my local electrical shop has I'd temporarly bypass the breakers for testing but until the stores open on Tuesday that will have to wait.      While I've been dealing with this problem for a while the idea that it probably was the breakers only occurred to me on Friday.

Yea,    I'm super careful with this higher voltage.      But what really sux is that I had Conext exchange the controller (2 week delay because of this) and if I do find that the problem wasn't the controller (Conext tech service believed it was a bad controller) then I've created a lot of expence and wasted time for both Conext and myself.      Conext tech support was very knowlageble as we went through my system with my multi- meter for about an hour.

Photowhit · May 2016

Heck it's temporary, I'd bet you can get some split bolt connectors that would work for you at WalMart, but I'm sure you could get them at any hardware store, farm supply is likely to have them also. If you're sneaky and promise to put them back! You could borrow a couple off of a telephone pole. Most have a ground wire going from top to bottom any that have or have had a box of some sort connected will likely have a split-bolt connecting them...

WaterWheel · June 2016

After bring out a solar professional the letter I just sent to Conext customer service explains it best. Remember that their customer service has been great with me, very knowledgeable on the phone, and quickly sent me a replacement controller.

Hello XXXXXX,

An interesting update on this 2nd MPPT 80 600 charge controller. The 2nd controller you sent me preformed exactly the same as the original. With 8 panels (cloudy sky) the Conext SCP was showing 283v with .2 amps coming in and .9 amps at 48v going out; the same as the last 80 600 controller which I sent back. Separate meters matched what the Conext battery monitor and SCP were reporting. As you know this controller's spec sheet and installers manual show that this controller requires at least 230v to function at full output so we are well above that threshold voltage.

I didn't want to attempt to exchange the controller again without bringing out a solar professional (Mike Hoover with Greenpoint Wind and Solar) to double check my work. After much testing Mike tried adding 2 more panels (10 panels total) to the string and the controller suddenly started working at 323v input and putting 12.4amps at 49v into the partially discharged battery bank.

With 14 panels in the string the controller input was 408v at 2.3 amps (remember it's a cloudy day) and was putting 17 amps in the battery.

And just for fun we maxed the number of panels the controller can accept and stay under 600v in strong sun so...

15 panels on a cloudy day and the controller was receiving 445v and was putting 19.6 amps into the batteries.

Obviously these controllers require over the published 230v to operate. Unfortunately while I can get away with 15 panels during the hotter months with this arrangement I'd need to remove one panel in the winter to stay under the 600v maximum voltage this controller can accept. Mike suggested just keeping the controller but it would mean not using 2 of my panels.

Are you guys experiencing a batch of bad controllers or are the minimum voltage specs for these controllers wrong?

Spencer Boyd

WaterWheel · June 2016

Update,     Kept the 14 panels on 1 string and second controller worked for a total of 2 days before it stopped sending current to the partially discharged batteries.     The SPC showed that the controller was seeing over 400 v.

After 2 weeks of Conext looking at software version, wiring diagrams, and their tech department trying to replicate the problem I was having using controllers they had on hand running the same software version they decide to send me a 3rd controller.

This 3rd controller has at least one different component in it (earth ground bar is different).     I called Mike (local solar guy) and invited him to join me in the install but he declined saying he didn't see where he would do anything different than I had done on the previous install.       It wired up easily and worked so well I'm still wondering what went wrong with the two previous controllers.      This is day two and it is still functioning perfectly.

I find it hard to believe that I had received two defective units in a row but I (and Mike the local solar installer) can't find any fault to how my system is wired.      Tech support couldn't find any wiring problems from the wiring schematic either.
Either way I'm just happy to now be able to program the correct absorb and float voltages for my batteries.

Conext (Scheider) Tech support was quick to assist both by email and phone during this long process.     I still believe that Conext makes a great product and I somehow got 2 bad controllers.

Changing charge controllers

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