2000k system only puts out 500 watt why?

[jflorey2]

What is your Opinion of this MPPT cc? Anyone ever use this one? Past experience appreciated! I can't find any warrenty info

Might work, but probably won't. Here's the troubling phrase:

"ACCEPT 18V TO 34V solar panel"

A real MPPT controller accepts higher voltages than that. If your highest array voltage is 18 volts you won't get any benefit from an MPPT controller on a 12 volt system, and if the highest voltage the thing can handle is 34 volts it won't even work with most 24 volt systems. (Open circuit voltage on a 24 volt array is around 40 volts.)

I suspect this is a standard PWM controller with fancy wording.

In general, you get what you pay for.

[sensij]

I just checked it is set to ONL. When you short press through the setting it's 27.0 off voltage first. 23.9 On voltage second. When the cc turns off the panel voltage climbs to 34v when the cc is on the panel voltage falls to 28v.

Ok, your understanding of ON and OFF is still not right, but the voltages are at least set in the correct order. The 27.0 volts is the ON voltage... when the relay turns ON, the solar panels are disconnected from the battery (and would be connected to the dump load, if you had one). Once the relay turns ON, since the battery is no longer getting charged, the voltage will gradually fall. Once it hits the OFF voltage of 23.9 V, the relay turns off again, reconnecting the array to the battery and allowing charging to begin again.

These voltages are definitely not ideal. By letting the voltage fall to 23.9 V before starting to charge, you are allowing the battery to regularly drop below 50% SOC. By ending the charge at 27.0 V, it is being prevented from ever fully charging, which would occur with several hours of topping off at something closer to 29 V. This combination is a recipe for early battery death. The default settings were pretty good... what motivated the change?

Some wild guesses.... The fact that you got rapid cycling between 23.9 V and 27.0 V is a bad sign, especially with an AGM battery that should probably have low internal resistance. It also might be a clue to explain how the solenoid burned up... it was probably intended to actuate the relay for short periods of time, normally, just the time it takes the battery to rest from 28.8 to 27.2 volts. By keeping the relay mostly on for the entire drop from 27.0 V to 23.9 V, during periods with no inverter load, the power consumption of the relay itself is all that will drive the battery voltage to the level at which charging can begin again (ignoring battery self consumption). That might lead to overheating of the relay, and premature failure.

The sky just finally cleared off at 2.51pm temp 70F to 72F panels peaked at 35.1volts with panels pointed directly at the sun but the full sun only lasted about 10 minutes before light clouds moved back in and out so the voltmeter reading is going from 35.8 to 34.3. The way it looks the sky might clear off in a few hours though. The only thing hooked to the 7 panels is the meter. I don't know if a voltmeter would cause the volts to fall from the panels. I just wish I could get a correct current reading.

A fluctuating Voc reading isn't a good thing. Voc isn't going to change with the amount of sunlight... another forum member proved that Voc could even be measured by moonlight. Voc is sensitive to cell temperature, but fluctuations like you described don't sound temp related. Bad measurement is always a possibility, but a high resistance leak could also explain it (meaning, the open circuit in Voc isn't truly open). If you really want to understand what is going on, you'll need to disconnect the panels from the combiner and measure the Voc of each individually. Measuring Isc when you have a trustworthy meter is a good idea too, although that measurement is very sensitive to sunlight and so you'll need to pay attention to the time and conditions at which the measurement is made.

[jflorey2]

Without a dump load, when the divert relay actuates, the PV circuit is just open, which shouldn't hurt anything.

Well, there's only the one relay there on the diagram. Are you thinking it has one set of NC contacts (connecting PV to battery) and one set of NO contacts? (connecting dump load to battery) Or am I missing another means of control?

[charles2,david000k]

Seems like there are a fair number of incentives for that right now.

But in the long run the utility has costs. They have powerlines, transformers and transmission lines to maintain. They have powerplants to build and maintain and fuel. And providing you with a free service to 'store' your electricity for you means that, in the long run, they go bankrupt (or they have to raise everyone else's rates.)

The new model seems to be a monthly fee that is basically a "storage" fee that goes towards maintaining their infrastructure. That seems pretty fair. For us it's $5 a month, and we get a lot for that money. APS just raised theirs to $21 a month, and there's been a lot of hoopla over that.

I do agree infracture does need to be kept up with and they did just have to come through and replace a good 80% of our poles and lines here but fuel cost would be next to nothing if every roof not in current use had at least 3k to 4k of panels on it. I think it would level out the fuel cost. An you are right you really can't do a even trade when they have to keep up the lines and all. Honestly I would be happy with a halfway point of .05 cent Kwh, keep electrical inspection fee, no application fee, a lower connection fee, and get rid of the $200 per year membership fee.


Speaking of inspection do you know of any UL approved MPPT charge controler in the 24 volt and 100 amp rang. I been looking but haven't found any yet and I know my electrical inspector will fail me on it he gave me a hard time when I did my rough in for going by 2015 nec code when we go by 03 or 04 code here it all came down to wire length 04 was 7 inches out the box and 2015 is 9 inches I think but I would have to dig out the nec book I got. Either way he made me cut 2 stinking inches off all my wires on the spot but I passed.

[sensij]

Well, there's only the one relay there on the diagram. Are you thinking it has one set of NC contacts (connecting PV to battery) and one set of NO contacts? (connecting dump load to battery) Or am I missing another means of control?

Yes, exactly. The two terminals on the sides are for the NO contact. The two terminals on the bottom are for the NC contact. Some of what I've written above is probably not perfectly correct, but doesn't change the functionality as installed. I had envisioned the generation source (PV or wind) on a common contact switching between the two outputs. However, another look at the drawing linked below suggests that the contacts are separate, perhaps to keep the exposed NO contact from being energized by the PV system (and a safety risk) when the dump load is not connected and the relay is active. When wired for diversion mode, the dump load is put in parallel with the battery, which makes more sense than a SPDT switch would.

http://www.mwands.com/images/controller/MW440ECCDIG_12V_Setup.jpg

[charles2,david000k]

Ok, your understanding of ON and OFF is still not right, but the voltages are at least set in the correct order. The 27.0 volts is the ON voltage... when the relay turns ON, the solar panels are disconnected from the battery (and would be connected to the dump load, if you had one). Once the relay turns ON, since the battery is no longer getting charged, the voltage will gradually fall. Once it hits the OFF voltage of 23.9 V, the relay turns off again, reconnecting the array to the battery and allowing charging to begin again.

These voltages are definitely not ideal. By letting the voltage fall to 23.9 V before starting to charge, you are allowing the battery to regularly drop below 50% SOC. By ending the charge at 27.0 V, it is being prevented from ever fully charging, which would occur with several hours of topping off at something closer to 29 V. This combination is a recipe for early battery death. The default settings were pretty good... what motivated the change?

Some wild guesses.... The fact that you got rapid cycling between 23.9 V and 27.0 V is a bad sign, especially with an AGM battery that should probably have low internal resistance. It also might be a clue to explain how the solenoid burned up... it was probably intended to actuate the relay for short periods of time, normally, just the time it takes the battery to rest from 28.8 to 27.2 volts. By keeping the relay mostly on for the entire drop from 27.0 V to 23.9 V, during periods with no inverter load, the power consumption of the relay itself is all that will drive the battery voltage to the level at which charging can begin again (ignoring battery self consumption). That might lead to overheating of the relay, and premature failure.



A fluctuating Voc reading isn't a good thing. Voc isn't going to change with the amount of sunlight... another forum member proved that Voc could even be measured by moonlight. Voc is sensitive to cell temperature, but fluctuations like you described don't sound temp related. Bad measurement is always a possibility, but a high resistance leak could also explain it (meaning, the open circuit in Voc isn't truly open). If you really want to understand what is going on, you'll need to disconnect the panels from the combiner and measure the Voc of each individually. Measuring Isc when you have a trustworthy meter is a good idea too, although that measurement is very sensitive to sunlight and so you'll need to pay attention to the time and conditions at which the measurement is made.

I changed the voltage becuase I came home one day and the entire building smelt of burnt batteries. When I checked the batteries they were so hot the plastic battery casing had started to melt. long story short my entire bank burnt up so I lowered the incoming voltage and replace batterys. I will change the 23.9 up to 24.5 and my 27.0 to 30.0 if that is any better I can't go past 32 though or I start blowing fuses.

It's not but should the negative side of my battery bank be grounded to earth?

I checked again to keep you all updated 33.2 to 33.6 on 6 panels and panel 7 is at 34.2 clear blue skies temp about 70F and sun almost straight up in the sky. All the panel were test by themselves disconnected from everything else reading were taken from panel mc-4 connectors .

[jflorey2]

I do agree infracture does need to be kept up with and they did just have to come through and replace a good 80% of our poles and lines here but fuel cost would be next to nothing if every roof not in current use had at least 3k to 4k of panels on it.

Problem is that the utility still has to provide peak power at a time (around 7pm) where there is no solar.

Speaking of inspection do you know of any UL approved MPPT charge controler in the 24 volt and 100 amp rang.

You could use a Magnum PT-100 for that. That's a PWM, but if the voltages you list are correct, you won't get much benefit out of an MPPT. MPPT's are great when your input voltage is significantly greater than your battery voltage, but with if you are really getting 32 volts from your array open circuit then you're going to be getting closer to 24-28 volts under load, which is what your battery needs anyway.

If you are dead set on MPPT, the Outback FM80 will give you 80 amps which will likely be enough for you. You'll peak shave a bit if your rated (STC) current is 100 amps, but only during perfect conditions (i.e. cloud lensing.)

[JoeBlow]

In use and working great.

Yes, exactly. The two terminals on the sides are for the NO contact. The two terminals on the bottom are for the NC contact. Some of what I've written above is probably not perfectly correct, but doesn't change the functionality as installed. I had envisioned the generation source (PV or wind) on a common contact switching between the two outputs. However, another look at the drawing linked below suggests that the contacts are separate, perhaps to keep the exposed NO contact from being energized by the PV system (and a safety risk) when the dump load is not connected and the relay is active. When wired for diversion mode, the dump load is put in parallel with the battery, which makes more sense than a SPDT switch would.

http://www.mwands.com/images/control..._12V_Setup.jpg

I just wanted to step in and defend this little solenoid charger. It is actually a decent charger and can handle 400amp. The instructions show that you install this item in a way that the charging battery bank never gets fully disconnected and the "dump" load just saps the power away from the battery. I realized this and tested the relay in a different way. The top lugs are simply a cutoff "to keep the on/off thing more simple" which in default setting it "makes a connection" all the time, then it will cut off the supply to the batteries. The lower lugs are supposed to be used for a system requiring a divert, which is "disconnected from" each other by default. On one lug the solar panels are connected and then it runs from there to the battery remaining always connected. The other lug goes to your divert system. This is the way the instructions tell you to do it.

Here's what I did.
I ran two wires from my panels fuse, one to a top lug, and the other to a lower lug. then I ran my "Primary bank" to the upper lug, and my divert to the lower lug. Now when my system diverts it is completely disconnected from one another when they are charging. I have found that this work perfectly and I get a great charge and use from my batteries. What I would suggest though is that a better charge controller is used, these solenoids can be used on any charger (I have seen them used with normal CC of all types. never tried) I am going to test that option too.

BTW I am at 600watts in panels and I can keep (with divert to second bank) 7 nearly charged by the end of the light period. The original poster needs a little more storage for his system. My first set of batteries were FRIED! because of my ignorance and I learned that I needed more. I would suggest double checking if not triple checking the batteries health with a battery tester. You can get one at Harbor freight cheap.

Lol, sounds like I predicted that one

[charles2,david000k]

Problem is that the utility still has to provide peak power at a time (around 7pm) where there is no solar.


You could use a Magnum PT-100 for that. That's a PWM, but if the voltages you list are correct, you won't get much benefit out of an MPPT. MPPT's are great when your input voltage is significantly greater than your battery voltage, but with if you are really getting 32 volts from your array open circuit then you're going to be getting closer to 24-28 volts under load, which is what your battery needs anyway.

If you are dead set on MPPT, the Outback FM80 will give you 80 amps which will likely be enough for you. You'll peak shave a bit if your rated (STC) current is 100 amps, but only during perfect conditions (i.e. cloud lensing.)

This whole 34 volt thing really bugs me. Is this really normal behavior for solar panels to drop off 4 volt's with in the first year? Granted I can not get a accurate reading on my current but when Missouri Wind and Solar tested the panels all they could get on current was 5 amps at 33 volts no higher on any of the panels and they told me the panels are still working properly and within warranty limits. I mean I don't know jack about solar compared to you guys but it just doesn't seem right. I know they drop off but from my understanding it's over a 25 year span at a slow decline not rapid drops. I mean who's right the licens tech who came out spent two days going over everything and told me the panels and cc are bad or the unlicensed salesmen. My gut tells me to listen to the guy who went to school but then again he could of slept through class. 34vX5a=175w That a 75 watt drop during peak time.

[charles2,david000k]

I just wanted to step in and defend this little solenoid charger. It is actually a decent charger and can handle 400amp. The instructions show that you install this item in a way that the charging battery bank never gets fully disconnected and the "dump" load just saps the power away from the battery. I realized this and tested the relay in a different way. The top lugs are simply a cutoff "to keep the on/off thing more simple" which in default setting it "makes a connection" all the time, then it will cut off the supply to the batteries. The lower lugs are supposed to be used for a system requiring a divert, which is "disconnected from" each other by default. On one lug the solar panels are connected and then it runs from there to the battery remaining always connected. The other lug goes to your divert system. This is the way the instructions tell you to do it.

Here's what I did.
I ran two wires from my panels fuse, one to a top lug, and the other to a lower lug. then I ran my "Primary bank" to the upper lug, and my divert to the lower lug. Now when my system diverts it is completely disconnected from one another when they are charging. I have found that this work perfectly and I get a great charge and use from my batteries. What I would suggest though is that a better charge controller is used, these solenoids can be used on any charger (I have seen them used with normal CC of all types. never tried) I am going to test that option too.

BTW I am at 600watts in panels and I can keep (with divert to second bank) 7 nearly charged by the end of the light period. The original poster needs a little more storage for his system. My first set of batteries were FRIED! because of my ignorance and I learned that I needed more. I would suggest double checking if not triple checking the batteries health with a battery tester. You can get one at Harbor freight cheap.

Lol, sounds like I predicted that one

Mine is set up in disconnect mode and the inverter monitors the bank power also if the bank falls to a certain voltage it uses grid power to feed the home and charge the batteries until the bank holds a proper voltage what those inverter set points are I have no clue at the moment but I do know the cc will read 28v at night when the bank goes dead and the inverter start to charge the bank it also has a desulfate setting which you have to manually activate. The inverter is picky when it comes to the battery that's another reason I had to swap out the batteries the first time.

add later. What are your peak charging amps/current going through the solenoid to your battery bank? I was told by the retailer not to feed no more than 200 amps to the solenoid with 4 AWG braided copper tin coated wire but that is just what I was told.

[sensij]

This whole 34 volt thing really bugs me. Is this really normal behavior for solar panels to drop off 4 volt's with in the first year? Granted I can not get a accurate reading on my current but when Missouri Wind and Solar tested the panels all they could get on current was 5 amps at 33 volts no higher on any of the panels and they told me the panels are still working properly and within warranty limits. I mean I don't know jack about solar compared to you guys but it just doesn't seem right. I know they drop off but from my understanding it's over a 25 year span at a slow decline not rapid drops. I mean who's right the licens tech who came out spent two days going over everything and told me the panels and cc are bad or the unlicensed salesmen. My gut tells me to listen to the guy who went to school but then again he could of slept through class. 34vX5a=175w That a 75 watt drop during peak time.

You are really hung up on the wrong thing. A properly functioning panel would never operate at 38 V or 34 V, unless it is extremely cold out. The panel produces maximum power at Vmp, which for your panels is 30.9 V. If they are warmer than 25 deg C, that value will drop. The panels in my grid tie array have a Vmp of 30.3, but on a hot summer day, they will drop down to around 25 V.

The only way to get a panel to operate consistently at Vmp is to have a charge controller (or grid-tie inverter) with an MPPT function. Without MPPT, you can sort of get close with 24 V panels that have a Vmp of 34-35 V... by the time you factor in temp corrections, the actual maximum operating voltage point should be close to the ideal charge voltage.

The fact you are measuring ~34 Voc on all the panels *could* be a sign of degradation. It could mean that your meter is pulling a bit more current than it should when it is making the measurement, and dragging the voltage down. Do the leads get warm at all? However, until you have a good way to measure operating voltage and current and be able to track it over time *and* have an mppt charge controller that is attempting to get the maximum power from the panels, it is almost impossible to prove that the system is or is not at warrantied performance. The only way I know how to do it is to track and plot that power over time, and compare it to what a PV modeling system would show the power to be under those conditions and with certain loss assumptions. Truly clear sky day-to-day comparisons can be powerful, once you understand the effects of temperature and solar position on the array's output.

[JoeBlow]

Mine is set up in disconnect mode and the inverter monitors the bank power also if the bank falls to a certain voltage it uses grid power to feed the home and charge the batteries until the bank holds a proper voltage what those inverter set points are I have no clue at the moment but I do know the cc will read 28v at night when the bank goes dead and the inverter start to charge the bank it also has a desulfate setting which you have to manually activate. The inverter is picky when it comes to the battery that's another reason I had to swap out the batteries the first time.

add later. What are your peak charging amps/current going through the solenoid to your battery bank? I was told by the retailer not to feed no more than 200 amps to the solenoid with 4 AWG braided copper tin coated wire but that is just what I was told.

I questioned the reliability of this solenoid for obvious reasons. They assured me it would support my future plans, which isn't nearly 400, more like below or at the 200 mark. I would imagine the 400amp would be a peak load, not sustainable. I notice heat build up in the solenoid which in my eyes it tells me that I am burning power, however most CC units will heat up. I have 100Ah running on my system now and they are charged by 2pm after 60% drain the night before. This is while the house is running on the inverter. I don't run major appliances on it right now because I need to expand. My point in this blah blah! lol, is if I can maintain and nearly over fill my 100ah storage in the afternoon while in use, I feel that your battery setup is too small for your needs. I am not a pro, I am about 5 months into a really smooth solar life. I installed everything and after I fried my first set of batteries I realized I needed more AH to back up what I took. Since then it has been an effortless system.

6 100W 12V Renogy Panels
100ah storage
I pull about 10amps with my inverter while my batteries slowly climb up.

Inverter is 2,000watt
I pull a little over 30amps during average day

[charles2,david000k]

You are really hung up on the wrong thing. A properly functioning panel would never operate at 38 V or 34 V, unless it is extremely cold out. The panel produces maximum power at Vmp, which for your panels is 30.9 V. If they are warmer than 25 deg C, that value will drop. The panels in my grid tie array have a Vmp of 30.3, but on a hot summer day, they will drop down to around 25 V.

The only way to get a panel to operate consistently at Vmp is to have a charge controller (or grid-tie inverter) with an MPPT function. Without MPPT, you can sort of get close with 24 V panels that have a Vmp of 34-35 V... by the time you factor in temp corrections, the actual maximum operating voltage point should be close to the ideal charge voltage.

The fact you are measuring ~34 Voc on all the panels *could* be a sign of degradation. It could mean that your meter is pulling a bit more current than it should when it is making the measurement, and dragging the voltage down. Do the leads get warm at all? However, until you have a good way to measure operating voltage and current and be able to track it over time *and* have an mppt charge controller that is attempting to get the maximum power from the panels, it is almost impossible to prove that the system is or is not at warrantied performance. The only way I know how to do it is to track and plot that power over time, and compare it to what a PV modeling system would show the power to be under those conditions and with certain loss assumptions. Truly clear sky day-to-day comparisons can be powerful, once you understand the effects of temperature and solar position on the array's output.

Just a thought but would a 1000 Watt high pressure sodium or metal halide grow light work to cut out the sun shading and angle problem?

[JoeBlow]

Just a thought but would a 1000 Watt high pressure sodium or metal halide grow light work to cut out the sun shading and angle problem?

lol, thats funny you said that. I just watched somebody hook a 100watt panel up under a 1,000 hps light and it actually started to charge the battery. I didnt see any amperage tests but it would be interesting to see what it would do. A factory that uses HID lighting could recoupe their power loss if you could establish a good amp flow.

[charles2,david000k]

lol, thats funny you said that. I just watched somebody hook a 100watt panel up under a 1,000 hps light and it actually started to charge the battery. I didnt see any amperage tests but it would be interesting to see what it would do. A factory that uses HID lighting could recoupe their power loss if you could establish a good amp flow.

you could never get back out what you put in and you would have to position the light directly over the panel I thought of it because I seen panels tested on a video in a solar panel manufacturing plant but I don't know if they are using 500W, 1000W, or two 1000W bulbs in different light spectrums.