Problems with output amps

[Vic]

   ...   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

[Simonbr]

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?

[Vic]

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

[Simonbr]

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.

[Vic]

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

[Simonbr]

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?

[boB]

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

[FNG]

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.

[FNG]

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

[Simonbr]

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.

[Simonbr]

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

[Simonbr]

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.

[boB]

What is the wire gage to the PV, Simon ?

[Simonbr]

I’m using 10 awg

[Vic]

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