I have a Midnite classic 150 with 4x 350w panels, two pairs series then paralleled. I can confirm the output is at 20a 77.6v range so I’m pretty sure there isn’t a problem with the connection. My problem is the output to my battery isn’t getting my configure 84a, it’s bouncing all over the place. It does reach 71.5 once in a while but then goes back down. Today the sun is out and there are no clouds at all. Any thoughts on why the output amps are all over the place?
Hi Simonbr,
In full sun at solar noon, with the PVs at right angles to the sun, and no shade, you should expect as much as 1050 Watts from your four PVs.
What is your battery voltage?
If you have a 12 v battery, you could see Classic output currents in the 80 A range, under ideal conditions.
As you know, the Classic defaults to about 84 A Maximum, as a current Limit setting, if there is sufficient input power from PVs.
Vic
Thanks Vic.
I am not sure what the battery voltage is either.
Is that 20 amps to the battery and 77 volts input from the PV ? If so, then we would need the voltage at the battery to help determine what is going on.
77V and 71V is about right for a "48V nominal" PV array at times. Lower PV input voltage if it is hot out.
boB
Thanks for the reply. I am on a 12v system. I thought It would handle more then just 1050w and over panelling would help keep it at a more consistent max output amperage for charging. I have a total of 1600w so I am not sure why the amps where jumping all over the place.
Quote from: boB on June 18, 2022, 03:03:47 PM
Thanks Vic.
I am not sure what the battery voltage is either.
Is that 20 amps to the battery and 77 volts input from the PV ? If so, then we would need the voltage at the battery to help determine what is going on.
77V and 71V is about right for a "48V nominal" PV array at times. Lower PV input voltage if it is hot out.
boB
I’m using 12 volts, the 20 amps is what I measure coming from the pv and the 77 range was the open circuit voltage.
Simon,
PV module watt Vmp and Imp ratings are at Standard Test Conditions (STC). This is with 1,000 watts of illumination per square meter, and at a solar cell temperature of 25 degrees C (77F). When in the sun, the IR radiation from the sun (and losses in the cells), raises the cell temperature, this reduces the cell voltage, and, therefore the power that the cells/PV module can produce. The common derating value is nominally 77% of the STC power rating, at solar noon, with PVs at right angles to the sun, etc.
A certain amount of over-PVing on Classics is fine, within limits.
So, you said that you have 1600 watts of input into the Classic. Four of the 350 watt PVs, should yield an STC power of 1400 watts, nominal. So, do you have additional PVs, accounting for that additional 200 watts?
What are the Vmp, and Imp ratings of the 350s? What is the string configuration to the other 200 watts (of assumed PVs), and what are the Vmp and Imp of those/that PV/s?
Thanks for the added info, Vic
Thanks for explaining all this info. I only have a total of 4 panels. 2 in series paralleled to the other 2 in series
Second image
Hi Simon,
Thanks for the info.
Two strings of two of those 350s should be fine on your Classic, for a 12 V system.
I had guessed that you might have some additional PVs, which might not have been too compatible with the 350s, but this is not the case.
You might want to re-torque all of the cable connections on the PV side of the Classic, and on the battery side of the Classic. It is common for copper-compression connections to relax, after the initial torquing of these screw type connections. This can result in poor connections, especially when high currents are flowing in these cables. You should probably check all battery cable connections, and re-troque, as well.
Good Luck, Vic
Am thinking that there might be a bit of a loose connection somewhere.
I'm not sure what the problem is ?
20A at 77V should equate to around 100+ amps at the output to the 12V battery, LESS Classic efficiency, which should still put you up around the maximum output current/power at 12V.
What is your output current to the battery and the battery voltage ?
Or, power ?
Are you seeing current limiting from the Classic ? You very well may especially on edge of cloud events which can take the irradiance even higher than nameplate rating.
But you will rarely get nameplate rating in normal hot weather. Usually a bit less. Sometimes 20% less.
boB
Ok I think I get it now, so you can safely say that you only get 80% of what your pv can push on a nice day because of the heat, so for my 4x 350 watts panels that would be 20% of 1400w, 1120w. Using the formula a=p/e I can figure out what amperage I have while charging, so the closer I get to my bulk set point the amps will be lower. In my case I have it set at 14.4v so I would see an output of 77.7a once bulk is complete.
I also have the wiz bang shunt and have configure in the hidden menu to only allow 84a to the battery, not in the normal limits option on the classic. I did this because I have a dc fridge and an inverter running and didn’t want more then 84a going into the battery but knew that I might be stealing 10ish amps for the fridge and inverter. Last year this was fine because I only had 2x 6v 420aH batteries that only required 42a max amps. So the MPPT would push out closer to the 52a. This year I doubled the battery bank so I have 4x 6v series/paralleled to double to 12v 840aH. I can assume that my current setup doesn’t reach the top end of my 82a + 10ish amp.
So a couple questions with all this,
1. Does the wiz bang current limiting work the way I think? I don’t have anything connected after the shunt, the fridge and inverter are all connected before.
2. Would adding 2 more 350w panels, one to each series, be worth it? This would give me 2100w (1680w at 20% loss) with an opportunity of 116.6a, if the classic would handle it. Another option is I have an epever 40a MPPT I can use for the other 2 panels, allowing me the full 40a with the full 77.7a from the classic and just allowing the whiz bang to limit the end amps to the battery. This would allow me above the 96a classic threshold when needing the full 84a battery charging + current usage like fridge and inverter demands.
Quote from: Simonbr on June 19, 2022, 09:13:59 AM
... 2. Would adding 2 more 350w panels, one to each series, be worth it? This would give me 2100w (1680w at 20% loss) with an opportunity of 116.6a, if the classic would handle it. Another option is I have an epever 40a MPPT I can use for the other 2 panels, allowing me the full 40a with the full 77.7a from the classic and just allowing the whiz bang to limit the end amps to the battery. This would allow me above the 96a classic threshold when needing the full 84a battery charging + current usage like fridge and inverter demands.
Little time right now, but, you do NOT want to go to strings of three PVs, especially on a 12V system.
Strings of three of the 350W PVs, will raise the string Voc, into a rough territory, and even the operating string Vmp will add extra heating on any MPPT Charge Controller (CC), especially on a 12 V system. The greater the voltage difference between the battery voltage, and the string voltage, the less efficient is the CC, resulting in more heat, and some other details, like current and voltage Jitter, etc.
The operating Voc will vary, depending on cold WX temperatures for your location ...
More later, others will fill in, more detail. Good questions, though, Vic
Not sure what you mean about the fridge and other things being wired on the WB Jr. ?
One side of the WB Jr. should ONLY be connected to the battery negative terminal. Nothing else. Then on the other end of the WB Jr, all of the other negatives are connected.
The Classic will not put out more than 90 some amps before it self limits and can limit to a lower value if it gets too hot.
Also, at the end of Bulk charging, the Classic's output current and power will go DOWN because the batteries do not accept more current when the Classic is keeping the voltage regulated at the Absorb voltage.
And the other things that Vic said. Thank you Vic !
boB
Sorry i might of not explained it well. I am trying to push 84a to the batteries, I know the classic 150 can only do 96a max. I configured the Wizbang to limit the end amps to 84, so if my fridge and inverter are not running (they are connected on the opposite side of the shunt going to the battery) it will limit to 84a. If the fridge and inverter are running, they will get as much current the CC has up to 96a of course.
i do know the current goes down for the absorption stage, i as just using setpoint for my reference in the math.
Would it be a better idea to do one of the following;
1. Add 2 more serried panels paralleled the the other 2 series, bringing up my current to 30a and keeping the Voc 77v?
2. Adding the new 2 350w panels on the Epever 40a MPPT and connecting the negative before the Whizbang shunt (to have the shunt keep limiting the battery charge current)
Quote from: Vic on June 19, 2022, 01:34:55 PM
Quote from: Simonbr on June 19, 2022, 09:13:59 AM
... 2. Would adding 2 more 350w panels, one to each series, be worth it? This would give me 2100w (1680w at 20% loss) with an opportunity of 116.6a, if the classic would handle it. Another option is I have an epever 40a MPPT I can use for the other 2 panels, allowing me the full 40a with the full 77.7a from the classic and just allowing the whiz bang to limit the end amps to the battery. This would allow me above the 96a classic threshold when needing the full 84a battery charging + current usage like fridge and inverter demands.
Little time right now, but, you do NOT want to go to strings of three PVs, especially on a 12V system.
Strings of three of the 350W PVs, will raise the string Voc, into a rough territory, and even the operating string Vmp will add extra heating on any MPPT Charge Controller (CC), especially on a 12 V system. The greater the voltage difference between the battery voltage, and the string voltage, the less efficient is the CC, resulting in more heat, and some other details, like current and voltage Jitter, etc.
The operating Voc will vary, depending on cold WX temperatures for your location ...
More later, others will fill in, more detail. Good questions, though, Vic
Would it be a better idea to add the extra 2 panels as another paralleled series to my existing 2 strings? This would bring up my current to 30A, im not sure what the maximum the Midnite can handle. Another option is add the other 2 on my space 40a CC. What do you think?
Quote from: Simonbr on June 20, 2022, 09:43:47 PM
Quote from: Vic on June 19, 2022, 01:34:55 PM
Quote from: Simonbr on June 19, 2022, 09:13:59 AM
... 2. Would adding 2 more 350w panels, one to each series, be worth it? This would give me 2100w (1680w at 20% loss) with an opportunity of 116.6a, if the classic would handle it. Another option is I have an epever 40a MPPT I can use for the other 2 panels, allowing me the full 40a with the full 77.7a from the classic and just allowing the whiz bang to limit the end amps to the battery. This would allow me above the 96a classic threshold when needing the full 84a battery charging + current usage like fridge and inverter demands.
Little time right now, but, you do NOT want to go to strings of three PVs, especially on a 12V system.
Strings of three of the 350W PVs, will raise the string Voc, into a rough territory, and even the operating string Vmp will add extra heating on any MPPT Charge Controller (CC), especially on a 12 V system. The greater the voltage difference between the battery voltage, and the string voltage, the less efficient is the CC, resulting in more heat, and some other details, like current and voltage Jitter, etc.
The operating Voc will vary, depending on cold WX temperatures for your location ...
More later, others will fill in, more detail. Good questions, though, Vic
Would it be a better idea to add the extra 2 panels as another paralleled series to my existing 2 strings? This would bring up my current to 30A, im not sure what the maximum the Midnite can handle. Another option is add the other 2 on my space 40a CC. What do you think?
Hi Simon,
The most important current for most MPPT CCs, is the output current. Think that the 30 Amps that you are referring to, is input current.
If you go to a third string of PVs on the Classic, then, really, each string would need a combiner box, and a breaker for each string in that box. Also, you might see a bit too much time spent in Amp Limit with the Classic ... that depends on the ambient temps, etc.
Sorry, still too little time to think more about this, now ... Later, Vic
I've taken a look at the classic string sizing tool and realized that 24v would work much better for me. I was already planning on moving over to a 24v inverter, looking at the Aims 3000w inverter charger. My dc fridge works on 12v or 24v and I supply the shoreline of my camper trailer with the 120v from the inverter, so I don't foresee any issues. I can always add a 24v to 12v if needed.
It also looks from the sizing tool that it would allow me add a third string paralleled or add a third panel to both existing string and not have my CC run in the higher amps, I would only need 42a + 10ish instead of my original 84a + 10a at the 12v system.
What are your thoughts of going this route?
Hi Simon,
For the power levels that you are dealing with, YES, 24 V would be better.
If you were to add a third PV in each existing string, might push the Voc situation, a bit. STC Voc for three of your PVs pushes the rated string Voc, to about 123 volts. Depending on your location, and the coldest temps you might be pushing Hyper Voc. OR, more likely, the Classic 150 would always be operating with high-ish Vin, and run, less efficiently.
You have probably input the lowest temps for your location, when running the Sizer, so, that will tell you a lot about operating conditions, and recommendations.
Of course, adding a third string would necessitate a combiner, and breakers (or fuses), one, per string.\
Hitting the road today, good luck, others will help on this, Vic
This is only used during the summer months, so the coldest is about 0c. We close up camp during winter and I store the batteries.
Yes my plan for adding a third string would be getting a combiner box. Looking online I see there are 10a and 15a versions. Since mine are all 10a strings would the 10a version be cutting it too close?
Thank you for taking the time and answering my questions.
Hi Simon,
Here is a MN Combiner. This one has room for three string breakers, so no room for any expansion:
https://www.solar-electric.com/mnpv3.html
EDIT to include this mnpv6 Link, not too much more expensive, and room to grow, if needed:
https://www.solar-electric.com/mnpv6.html
Here is a breaker, rated for 15 A DC, IIRC, the max Fuse Size for your PVs is 20A:
https://www.solar-electric.com/midnite-solar-mnepv-15-amps-circuit-breaker.html
Later, Vic
Quote from: Vic on June 21, 2022, 11:49:13 AM
Hi Simon,
For the power levels that you are dealing with, YES, 24 V would be better.
If you were to add a third PV in each existing string, might push the Voc situation, a bit. STC Voc for three of your PVs pushes the rated string Voc, to about 123 volts. Depending on your location, and the coldest temps you might be pushing Hyper Voc. OR, more likely, the Classic 150 would always be operating with high-ish Vin, and run, less efficiently.
You have probably input the lowest temps for your location, when running the Sizer, so, that will tell you a lot about operating conditions, and recommendations.
Of course, adding a third string would necessitate a combiner, and breakers (or fuses), one, per string.\
Hitting the road today, good luck, others will help on this, Vic
I've had my 24v system up for over a weak now and starting to get the adjustments pretty good. My issue with not getting better wattage is still there though. i want to be able to get at least 50 to 60 amps reading at the Wb but I am not getting there, today the sun was out with no clouds and I hit the 40's a couple times but not consistent enough IMO. I've included a screen shot of the MM graph from 8am to about 7pm.
Any ideas why this is happening?
Simon, I just came into this conversation but first thing to ask is, are you running any other DC loads at all on the battery side ?
Of course, the Classic's amperage being reported might be slightly off. I would trust the WB Jr. on what is going into the battery though.
boB
Quote from: Simonbr on July 08, 2022, 09:27:22 PM
Quote from: Vic on June 21, 2022, 11:49:13 AM
Hi Simon,
For the power levels that you are dealing with, YES, 24 V would be better.
If you were to add a third PV in each existing string, might push the Voc situation, a bit. STC Voc for three of your PVs pushes the rated string Voc, to about 123 volts. Depending on your location, and the coldest temps you might be pushing Hyper Voc. OR, more likely, the Classic 150 would always be operating with high-ish Vin, and run, less efficiently.
You have probably input the lowest temps for your location, when running the Sizer, so, that will tell you a lot about operating conditions, and recommendations.
Of course, adding a third string would necessitate a combiner, and breakers (or fuses), one, per string.\
Hitting the road today, good luck, others will help on this, Vic
I've had my 24v system up for over a weak now and starting to get the adjustments pretty good. My issue with not getting better wattage is still there though. i want to be able to get at least 50 to 60 amps reading at the Wb but I am not getting there, today the sun was out with no clouds and I hit the 40's a couple times but not consistent enough IMO. I've included a screen shot of the MM graph from 8am to about 7pm.
Any ideas why this is happening?
Simon,
Can you redo that screenshot and include battery voltage as well.
Simon,
Looking back through this, You sure could add a 3rd string of these modules even on a 12v system.
From what I am seeing you are getting about what I would expect, Warm summer days drop output a LOT, A good example is the 340 watt modules on my barn, This time of year the micro inverters report around 260-270 watts on a good day, When its cool int he fall and winter I see closer to the 340 mark
Quote from: boB on July 09, 2022, 12:12:23 AM
Simon, I just came into this conversation but first thing to ask is, are you running any other DC loads at all on the battery side ?
Of course, the Classic's amperage being reported might be slightly off. I would trust the WB Jr. on what is going into the battery though.
boB
Hello Bob, I only have a DC fridge that is running, 24v 2.5a
I have both amps that I look at, the output from the classic and the Wb, they seem to be correct when using loads as I have another shunt that calculats all my loads.
Quote from: FNG on July 09, 2022, 06:08:52 AM
Quote from: Simonbr on July 08, 2022, 09:27:22 PM
Quote from: Vic on June 21, 2022, 11:49:13 AM
Hi Simon,
For the power levels that you are dealing with, YES, 24 V would be better.
If you were to add a third PV in each existing string, might push the Voc situation, a bit. STC Voc for three of your PVs pushes the rated string Voc, to about 123 volts. Depending on your location, and the coldest temps you might be pushing Hyper Voc. OR, more likely, the Classic 150 would always be operating with high-ish Vin, and run, less efficiently.
You have probably input the lowest temps for your location, when running the Sizer, so, that will tell you a lot about operating conditions, and recommendations.
Of course, adding a third string would necessitate a combiner, and breakers (or fuses), one, per string.\
Hitting the road today, good luck, others will help on this, Vic
I've had my 24v system up for over a weak now and starting to get the adjustments pretty good. My issue with not getting better wattage is still there though. i want to be able to get at least 50 to 60 amps reading at the Wb but I am not getting there, today the sun was out with no clouds and I hit the 40's a couple times but not consistent enough IMO. I've included a screen shot of the MM graph from 8am to about 7pm.
Any ideas why this is happening?
Simon,
Can you redo that screenshot and include battery voltage as well.
Here is the added voltage, 8am to about 9pm
Quote from: FNG on July 09, 2022, 06:14:19 AM
Simon,
Looking back through this, You sure could add a 3rd string of these modules even on a 12v system.
From what I am seeing you are getting about what I would expect, Warm summer days drop output a LOT, A good example is the 340 watt modules on my barn, This time of year the micro inverters report around 260-270 watts on a good day, When its cool int he fall and winter I see closer to the 340 mark
Im looking this morning and my input PV is about 61v and 15.5a. From the labels on the panels all 4 are about 40 Voc and 10a, ran in series paralleled to give me 80v per string. I know there is voltage drop with about 60 feet of cable but does going down to 50v to 60v seem normal? It fluctuates with the sun and clouds of course, just didn't think it would drop this much.
What is the wire gage to the PV, Simon ?
I’m using 10 awg
Hi Simon,
Many folks say, that in full sun, with PVs at right angles to the sun, and reasonable outside temps, that one can expect PVs to yield about 77% of rated (STC) power (Amorphous PVs would have a considerably lower output power).
In the specs for your PVs, there should be ratings for Normal Operating Cell Temperature (NOCT), which, generally is not a bad guide on what to expect for more typical sun/wind/temps, etc.
As you know, STC conditions are measured with cell temp at 25 C, and exactly 1kW per sq meter of flashtube illunimation.
Haze and humidity can reduce the illunimation, yet, often, the sun appears to be fully-bright, etc.
FWIW, people say ... Vic
Quote from: Vic on July 09, 2022, 05:10:03 PM
Hi Simon,
Many folks say, that in full sun, with PVs at right angles to the sun, and reasonable outside temps, that one can expect PVs to yield about 77% of rated (STC) power (Amorphous PVs would have a considerably lower output power).
In the specs for your PVs, there should be ratings for Normal Operating Cell Temperature (NOCT), which, generally is not a bad guide on what to expect for more typical sun/wind/temps, etc.
As you know, STC conditions are measured with cell temp at 25 C, and exactly 1kW per sq meter of flashtube illunimation.
Haze and humidity can reduce the illunimation, yet, often, the sun appears to be fully-bright, etc.
FWIW, people say ... Vic
So i guess its normal that you don't get full specs and also normal that it fluctuates depending on the sun and its angle.
I have one of the data sheets but it doesn't have anything about NOCT, it does have NMOT and the Vmpp that is at 33.27v, which makes sense for my 2 in series and the voltage drop with the length of PV cable I have. Does that make sense that this is the actual maximum voltage?
https://www.q-cells.us/dam/jcr:c622cdbc-dfce-4f64-ba84-82fc687b1118/Q_CELLS_Data_sheet_Q.PEAK_DUO_BLK-G8+_335-350_2020-07_Rev02_NA.pdf