Understanding Charge Controller Volts and Amps

[Dennis 1]

I'm having an issue understanding the volts and amps going to a CC.
Right now I have 4-100W Rich poly solar panels at 22.6VOC if I put 4 in series would be 4x22.6=90.4V and ISC is 5.86A
Then I have 2 HQST mono solar panels 21.6voc in series so 2x21.6=43.2V and ISC is 6.5A and 2 more at 21.3voc in series so 2x21.3=42.6V and ISC is 5.83A
They all run into a combiner box and on 3 - 15A fuses
Right now I have an HQST 150/60 CC when I add them together it comes to 176.2V which is larger than the 150V the CC can handle and 18.19A which seem to be fine. Even when the CC says it can handle 900w of panels.

 

[Rednecktek]

I'm having an issue understanding the volts and amps going to a CC.

OK, let's see if we can help straighten this all out a bit

Right now I have 4-100W Rich poly solar panels at 22.6VOC if I put 4 in series would be 4x22.6=90.4V and ISC is 5.86A

OK, sounds good. so 4s 100w panels then? 90.4v @ 5.86a

Then I have 2 HQST mono solar panels 21.6voc in series so 2x21.6=43.2V and ISC is 6.5A and 2 more at 21.3voc in series so 2x21.3=42.6V and ISC is 5.83A

So basically another 4s string that will put out 21.3*4= 85.2v at 5.83a (since mixing panels in series cuts everything to lowest common denominator).

They all run into a combiner box and on 3 - 15A fuses

That should put both strings in parallel and reduce the output voltage to 85.2v at 11.7a max

Right now I have an HQST 150/60 CC when I add them together it comes to 176.2V which is larger than the 150V the CC can handle and 18.19A which seem to be fine. Even when the CC says it can handle 900w of panels.

If you're getting that much voltage out of your combiner box there's something wrong. The combiner box should be paralleling the strings, not serial-ing them. You should see about 85v coming out of the combiner box. That's well within the limits of the SCC. Check that with a meter.

If you are getting 175v or so, then go with a Y-splitter and get out of the defective combiner box. With 2 strings you don't need fuses anyways.

 

[Ampster]

when I add them together it comes to 176.2V which is larger than the 150V the CC can handle

That could be an issue. The voltage specs are the importan ones not to exceed. You need to reconfigure to get voltage below the CC voltage. Also allow for the effect on low temperatures which will increase the voltage. The Wattage rating assumes voltage below the max and the CC will only pull the current it needs to serve the loads.
@Rednecktek explained it in more detail.

 

[sunshine_eggo]

I'm having an issue understanding the volts and amps going to a CC.
Right now I have 4-100W Rich poly solar panels at 22.6VOC if I put 4 in series would be 4x22.6=90.4V and ISC is 5.86A
Then I have 2 HQST mono solar panels 21.6voc in series so 2x21.6=43.2V and ISC is 6.5A and 2 more at 21.3voc in series so 2x21.3=42.6V and ISC is 5.83A
They all run into a combiner box and on 3 - 15A fuses
Right now I have an HQST 150/60 CC when I add them together it comes to 176.2V which is larger than the 150V the CC can handle and 18.19A which seem to be fine. Even when the CC says it can handle 900w of panels.

Limits are limits. Your 150/60 controller can handle a Voc maximum of 150V - including cold temperature voltage effects. It's also limited to 60A of OUTPUT AT battery voltage (60 * 14.5V = 870W for 12V, or 60 * 29V = 1740W for 24V, etc.).

There is also likely an unpublished PV input current limit. When it's not published, it's presumed to be the same as the output current limit.

Being able to output 900W doesn't mean you get to violate other limits to make that happen.

You've made a math error of some kind. Panels in series add voltage, current stays the same. Panels in parallel add amps, voltage stays the same.

So, #1 rule: NEVER break Voc limit. NEVER.

If you've actually done that, and the controller isn't fried, you're so so lucky.

Due to the difference between the two brands Isc, you shouldn't place the brands in series with each other - only themselves. Thus, you should arrange your panels in a 2S4P array 2S rich in parallel with 2S Rich in parallel with 2S HQST in parallel with the other 2S HQST.

This will result in a Voc of approximately 44V and an Isc of approximately 24A.

Alternatively, you can 4S the Rich and 4S the HQST and then put those two strings in parallel. The 2 HQST with higher current will be penalized about 10%.

Then you would have about 88V and 12A.

 

[Rednecktek]

Wow guys, all those responses in less than a minute? We need lives outside of here. ?

 

[sunshine_eggo]

Holiday weekend with no plans other than heavy auto maintenance and honey-dos.. I'd rather be in front of the computer even with today's cold front coming through... high of only 93!!!! Down 17° !!!!

 

[Rednecktek]

I'd rather be in front of the computer even with today's cold front coming through... high of only 93!!!! Down 17° !!!!

Man, I wish my boss would let me get away with that on the Persian Gulf runs... we honestly have no idea how hot the engine room is because the thermometer only goes to 50c/122f. It pegs in early May and stays there until mid November.

 

[Dennis 1]

OK, let's see if we can help straighten this all out a bit

OK, sounds good. so 4s 100w panels then? 90.4v @ 5.86a

So basically another 4s string that will put out 21.3*4= 85.2v at 5.83a (since mixing panels in series cuts everything to lowest common denominator).

That should put both strings in parallel and reduce the output voltage to 85.2v at 11.7a max

If you're getting that much voltage out of your combiner box there's something wrong. The combiner box should be paralleling the strings, not serial-ing them. You should see about 85v coming out of the combiner box. That's well within the limits of the SCC. Check that with a meter.

If you are getting 175v or so, then go with a Y-splitter and get out of the defective combiner box. With 2 strings you don't need fuses anyways.

Thats where I got the 175 by adding the 90 from the Rich panels and the 85 from the HQST. You say I should be seeing 85 coming out of the CC what happens to the 90 from the Rich panels. All 3 strings go to the Combiner Box and each has a 15A breaker. I just did this p and have shut it down in the house until I get it straightened out.

 

[Dennis 1]

Limits are limits. Your 150/60 controller can handle a Voc maximum of 150V - including cold temperature voltage effects. It's also limited to 60A of OUTPUT AT battery voltage (60 * 14.5V = 870W for 12V, or 60 * 29V = 1740W for 24V, etc.).

There is also likely an unpublished PV input current limit. When it's not published, it's presumed to be the same as the output current limit.

Being able to output 900W doesn't mean you get to violate other limits to make that happen.

You've made a math error of some kind. Panels in series add voltage, current stays the same. Panels in parallel add amps, voltage stays the same.

So, #1 rule: NEVER break Voc limit. NEVER.

If you've actually done that, and the controller isn't fried, you're so so lucky.

Due to the difference between the two brands Isc, you shouldn't place the brands in series with each other - only themselves. Thus, you should arrange your panels in a 2S4P array 2S rich in parallel with 2S Rich in parallel with 2S HQST in parallel with the other 2S HQST.

This will result in a Voc of approximately 44V and an Isc of approximately 24A.

Alternatively, you can 4S the Rich and 4S the HQST and then put those two strings in parallel. The 2 HQST with higher current will be penalized about 10%.

Then you would have about 88V and 12A.

So what you're saying is only 88V and 12A from the HQST panels and not the 90V from the 4 Rich panels get added together. Is that because the combiner box they end up in Parellel. I shut everything in the house down before I figured this out.

 

[Doggydogworld]

Thats where I got the 175 by adding the 90 from the Rich panels and the 85 from the HQST. You say I should be seeing 85 coming out of the CC what happens to the 90 from the Rich panels.

Series - add voltages, use the lower current
Parallel - add currents, use the lower voltage

All 3 strings go to the Combiner Box and each has a 15A breaker. I just did this p and have shut it down in the house until I get it straightened out.

3 strings? This is a problem. Your 42.6V string will pull the other two strings down to 42.6. Including your 4x100W Rich Solar string that wants to be at 90V.

You need 2 strings of 4 panels each. Put your two 21.6V HQSTs in series with the two 21.3V panels to get 85.8V. Not a perfect match for the 4x100W Rich Solar string, but close enough.

 

[sunshine_eggo]

So what you're saying is only 88V and 12A from the HQST panels and not the 90V from the 4 Rich panels get added together. Is that because the combiner box they end up in Parellel. I shut everything in the house down before I figured this out.

88V vs. 90V doesn't matter. They will actually always be at the same voltage - the lower of the two - because they are in parallel, and that will vary with cell temperature (lower temp = higher voltage). An array with 4S Rich in series in parallel with 4S HQST in series will be a 88-90V-ish array with about 11.6AIsc.

 

[Dennis 1]

Series - add voltages, use the lower current
Parallel - add currents, use the lower voltage


3 strings? This is a problem. Your 42.6V string will pull the other two strings down to 42.6. Including your 4x100W Rich Solar string that wants to be at 90V.

You need 2 strings of 4 panels each. Put your two 21.6V HQSTs in series with the two 21.3V panels to get 85.8V. Not a perfect match for the 4x100W Rich Solar string, but close enough.

Are you saying that I would get 85.8V instead of 90V andbe good enough for the 150V of the CC

 

[Dennis 1]

88V vs. 90V doesn't matter. They will actually always be at the same voltage - the lower of the two - because they are in parallel, and that will vary with cell temperature (lower temp = higher voltage). An array with 4S Rich in series in parallel with 4S HQST in series will be a 88-90V-ish array with about 11.6AIsc.

Thats what I didn't understand is you take the lowest voltage from the parellel string instead of adding all the voltages coming out of the combiner box going to the CC.

 

[Rednecktek]

Yup, when they parallel up the voltage will balance out to the lowest common voltage on the output. If you poke it with a meter you'll see in the 85v range and be good to go. If you're seeing lots more than that go back and look for shorts!

 

[TomC4306]

Thats what I didn't understand is you take the lowest voltage from the parellel string instead of adding all the voltages coming out of the combiner box going to the CC.

There should only be one voltage coming out of a combiner box. Thus the term combiner there shouldn't be multiple voltages coming out of a combiner box.

 

[TomC4306]

88V vs. 90V doesn't matter. They will actually always be at the same voltage - the lower of the two - because they are in parallel, and that will vary with cell temperature (lower temp = higher voltage). An array with 4S Rich in series in parallel with 4S HQST in series will be a 88-90V-ish array with about 11.6AIsc.

In addition, in the dynamic environment of a solar panel array with heat and breeze and cloud and birds and stuff the voltage is never never still.
Close-ish is good enough.

 

[CoolWill]

Wait... Wait... Did you measure the voltage at 170+ or did you just add the numbers together?

 

[daklein]

What voltage battery do you plan to charge? The CC will be most efficient with less voltage drop to the battery, but the solar panel voltage still needs to be somewhat above the battery voltage. 12V or 24V batt : do 4 strings in parallel of 2 panels each in series, VOC will be about 45v. 48V battery: do 4 panels series, 2 parallel strings, VOC will be about 90v. Either will still work for either battery voltage though. Dont' put all the 8 panels in series on one string, that will exceed the CC input voltage.

 

[sunshine_eggo]

Thats what I didn't understand is you take the lowest voltage from the parellel string instead of adding all the voltages coming out of the combiner box going to the CC.

You've made a math error of some kind. Panels in series add voltage, current stays the same. Panels in parallel add amps, voltage stays the same.

 

[Dennis 1]

Wait... Wait... Did you measure the voltage at 170+ or did you just add the numbers together?

Just added the numbers together