Need Help/Advice

[upnorth]

I checked my invoice and I have the MNPV3 combiner box. Would this have to be changed?

 

[GSXR1000]

When you are combining over 150V, you need the Midnite PV6-250 combiner to hold the higher voltage 300V breakers. He's probably referring to that. https://www.midnitesolar.com/produc...e=Combiners&productCat_ID=9&sortOrder=6&act=p

That would put the panels in parallel

 

[GSXR1000]

Here is an updated screenshot from right now. Still cloudy I guess.

you are MAXED out of solar charger the rest of your panels are being unused....

 

[SolarQueen]

Midnite confirmed you can share the existing negative wire, as long as it is properly sized to carry all the current. Since it was designed to do so with the strings combined, you should be good. That's good news, you only need to pull 1 wire. He also said if it were him, he'd turn off the breaker for the second string until you get it fixed, but you can get away without if you want the advantage of cloudy days getting more power. You'll just be stressing the controller a bit on sunny days.

I'm really mad at your supplier. He's got you running over 200V through breakers that are designed for 150V. Add that to the list to tell him to replace. You can get away with keeping the PV3, it's just the box, and you no longer need the finger bus bar that combines the strings (it is different in the 150V vs 250V unit, as the 300V breakers are double the width), but you need to replace the 150V breakers with 300V 15A breakers.

 

[SolarQueen]

That would put the panels in parallel

Exactly, which is how he currently has it, and we are working out how to change that. We're just figuring out what equipment he has, and what changes are needed.

 

[Hedges]

Here is an updated screenshot from right now. Still cloudy I guess.

Perfect.
800W, 61.7A at 13.4V. That's the most you can get. You're on a roll, just need 12 hours like that to fully recharge.

If you convert to a 24V inverter, you get twice as much power.

As SolarQueen said, if your breakers don't already have two-pole 150V breakers wired in series (for 300V), you need that because the PV panels are putting out 200V or more.

 

[upnorth]

I have been hoping for a full sun day but hasn't happen. I am just trying to decide the best route to take so wanted to confirm I understand what the options might be.....

1) Keep the 12V inverter and add another Midnite 250 charge controller. In this case I should get double what I am getting now but will be over-panelled. So approx. 1600 watts?

2) try to exchange for 24V inverter and with current set up (just one Midnite CC) the system will generate approx. 1700-1800 watts as per Hedges?

3) If I went with 24V inverter and another Midnite 250 CC what could I expect for Watts to be generated?? Would this boost it above the 1800 Watts?

A couple of questions. When talking about the size of breakers, do I just look in the combiner box and see what size of breakers are in there? Is it simply stamped on them?

If I did upgrade to 24V inverter, what size would I need in terms of Watts? Still 3000 Watt or smaller/larger?

Thanks everyone for their help and advice.

 

[Ryang]

I have been hoping for a full sun day but hasn't happen. I am just trying to decide the best route to take so wanted to confirm I understand what the options might be.....

1) Keep the 12V inverter and add another Midnite 250 charge controller. In this case I should get double what I am getting now but will be over-panelled. So approx. 1600 watts?

2) try to exchange for 24V inverter and with current set up (just one Midnite CC) the system will generate approx. 1700-1800 watts as per Hedges?

3) If I went with 24V inverter and another Midnite 250 CC what could I expect for Watts to be generated?? Would this boost it above the 1800 Watts?

A couple of questions. When talking about the size of breakers, do I just look in the combiner box and see what size of breakers are in there? Is it simply stamped on them?

If I did upgrade to 24V inverter, what size would I need in terms of Watts? Still 3000 Watt or smaller/larger?

Thanks everyone for their help and advice.

Ill answer question 3 and 4.

3. 24V inverter & midnite 250. Midnite can charge 62amps at 24v each. So if you had 2 of them you'd be producing 124amps total. 124ax24v = 2976w. So you would be using all of your panels power.

The inverter size it totally up to you. It depends how much power the cabin is drawing. You should do an energy audit to know what you need + a little leg room.

Really hope they trade in the inverter for you.

 

[Hedges]

A key problem to fix is that the inverter drained the battery too low. You need an inverter with suitable low battery shutdown, somewhere around 80% DoD.

 

[SolarQueen]

I'll answer the breaker question, I think Ryang did a good job with #3. If you have a Midnite PV3, you most likely have 150V breakers. They look like this. If they gave you 300V breakers, they will be double breakers, and end up looking like 4 breakers in a box designed for 3 breakers, so modification would have had to have been done. The 300V breakers look like this.

 

[GSXR1000]

why leave the inverter on when you are not there?

 

[upnorth]

Ok thanks for the info. To be honest just left the inverter on because I didn’t know to turn it off and didn’t realize it would drain the batteries.

 

[GSXR1000]

Ok thanks for the info. To be honest just left the inverter on because I didn’t know to turn it off and didn’t realize it would drain the batteries.

i would have thought the same. that is a lot of battery reserve.... at least it has shown the other design issues with this system

 

[Hedges]

I'll answer the breaker question, I think Ryang did a good job with #3. If you have a Midnite PV3, you most likely have 150V breakers. They look like this. If they gave you 300V breakers, they will be double breakers, and end up looking like 4 breakers in a box designed for 3 breakers, so modification would have had to have been done. The 300V breakers look like this.

How about low battery shutdown? I read spec for his model inverter as saying doesn't shut off until 10.2V.
Do you have a retrofit shutdown solution? Does Midnight charge controller have a signal which could be used to control inverter or a relay?

 

[SolarQueen]

How about low battery shutdown? I read spec for his model inverter as saying doesn't shut off until 10.2V.
Do you have a retrofit shutdown solution? Does Midnight charge controller have a signal which could be used to control inverter or a relay?

If we switch to a 24V system, the Victron BatteryProtect could do the trick. Available with or without Bluetooth. https://www.victronenergy.com/battery_protect/battery-protect

 

[Hedges]

If we switch to a 24V system, the Victron BatteryProtect could do the trick. Available with or without Bluetooth. https://www.victronenergy.com/battery_protect/battery-protect

Sounds good, except can't support an inverter/charger because only allows current in one direction.

Was hoping for a simple voltage setpoint controlling a power relay, or controlling a remote switch for the inverter.

I think his Midnight Classic has configurable ports which can switch based on state of charge or voltage, correct?

"AUX Function Definitions
VOLTS: Refers to the voltage threshold, or set point, or “At what voltage do you want to turn on/off the specified AUX port?”"

"AUX 1 Modes
SOC % Low
When State of Charge (SOC) reaches % LOW AUX 1 will turn OFF. As SOC goes up and reaches % HIGH, AUX 1 will turn ON. DELAY and HOLD can also be used to further control when AUX 1 will turn on/off.
SOC % High
When SOC reaches % LOW, AUX 1 will turn ON. As the SOC goes up and reaches % HIGH, AUX 1 will turn OFF. DELAY and HOLD can also be used to further control when AUX 1 will turn on/off."

 

[upnorth]

Anyone know what the wiz bang junior is for? This was with the package as well but it’s not hooked up because there was a part missing?

 

[Hedges]

Ammeter shunt with electronics. It lets current flow (perhaps also state of charge?) be accessed by other hardware.

Don't know if it would let the charge controller regulate current into battery while providing extra current needed by inverter. Would be ideal if it did, but haven't seen anything like that documented.

 

[upnorth]

If I change the system to a 24V is another midnite 250 going to be able to handle the full 3100 watt array? I have attached a form my Dad filled out with midnite and it seems to say I need a midnite 150 or 200 because they handle more power???

Solarqueen has been very helpful and mentioned the safety concern with the system as is but is it ok to leave like this for say the next few weeks until I have the system set up figured out? Or does one of the breakers need to be turned off?

I am hoping to get another mid nite 250 and swap the inverter for a 24V but just want to make sure the charge controller can handle it?
Thanks again to everyone for their help and comments.

 

[Hedges]

You can turn one breaker off. No harm in that.
Maybe in times of very little light, having both on would make more power.

The Midnight 250 can deliver 1700W into a 24V battery (at 28V, near full charge), so a second one would utilize all the panels.
The Midnight 200, and even more the 150, deliver more current and more watts than the 250. With lower Voc, of course.
The 150 will deliver 2300 to 2700W, depending on Vmp. That could fully utilize your array (because actual power generally peaks about 15% below STC)

If you give each series string of panels a different orientation, aimed at different time of day or different season, that will reduce peak power, fitting better within a given charge controller.