Different Solar Panels

billdean · December 2020

I have 3 solar panels. Two of them are exactly the same (200w, 24.335voc, 21.052vmp) the other is from a different manufacture (150w, 22.58voc, 17.85vmp). I am using a Morningstar TS_Mppt-60 CC. I don't understand what the best way to wire these to the controller. Would I series the 2 like panels to the combiner box and then just hook the odd panel in? Or would I be better off paralleling all 3 panels to the combiner box? Or series all 3 together to the combiner box? Too confusing and too much work climbing up and down to the roof. Anybody have any ideas how to correctly do this, if there is a correct way?

BB. · December 2020

It is more complicated than what you ask... Need to start from the beginning.

What is battery bank Voltage / AH rating / type (FLA, AGM, LiFePO4, etc.)?
What is the minimum temperature for your location (i.e., tropical island at 65F, or far north at -40F)?
Look up limits for controller: MPPT type (MorningStar has a PWM model that looks identical and named very similarly):

https://www.solar-electric.com/motr60ampmps.html

The TriStar TS-MPPT-60 MPPT is designed for off-grid PV systems as large as 3.0 kWp, and is rated for 60 amps at up to 150 volts PV open circuit. This product is extremely reliable since it has a robust thermal design, no internal cooling fan and no mechanical relays.

More or less, the input requirement of the TS MPPT controller is 150 VDC max (which works out to around 110 volts or less Vmp-array--Note we are looking for Vmp-array-cold to be less than 150 VDC (to not damage the controller).

Vmp-array minimum voltage is typically Vmp=17.5 volts @ 12 volt bak; Vmp-array=35 volts @ 24 volt bank; and Vmp-array=70 volts @ 48 volt bank.

Vmp-array "Optimum Voltage" is typically around 2x (roughly) Vbatt--I.e., 14.8 volts charging then 2x14.8v=29.6 volts Vmp-array optimum (up to Vmp-array~110 volts or so max for very cold climates). The controller works fine at any of those voltages, but is usually 1-2% or so less efficient closer to 110 Volts Vmp-array.

Your panels appear to be:

2x 200 Watts / 21.052 volts Vmp (are you sure? That is not a very standard voltage) = 9.5 Amps Imp
1x 150 Watts / 17.85 Volts Vmp = 8.4 amps Imp

At this point, waiting for your Battery bank voltage....

-Bill

billdean · December 2020

Thanks Bill for getting back with me. I have one 150 Vikram Eldora panel seen here: https://www.vikramsolar.com/wp-content/uploads/2016/04/ELDORA-150P-Micro-Series-1.pdf. and 2 x 200 watt Hightec solar panel seen here: https://www.continuousresources.com/collections/solar-panels-and-hardware/products/hightec-solar-200w-36-cell-12v-nominal-solar-panel-5-busbar

My battery bank is 4 T105 Trojan batteries for a total of 450 amp hours, I believe, and it is a 12 volt system. I have 2 TS-MPPT-60 Controllers. One controller has the set up above and the other has 3x 200 watt Hightec solar panels. This system is on an RV. Six months out of the year the RV gets used in the winter in Arizona. The other six months it is in storage in Michigan.

There is a huge difference on the output of the controllers. I have been trying different things but the bank with the 150 watt panel just does not preform well. I have a little bit of log data on the 2 banks. The left column is controller 1 and the right column is controller 2. My absorption rate is set to 14.82. This data is being logged in south western Arizona.

Date	Max Batt Voltage	Min Batt Voltage	Amp Hours	Watt Hours	Max Array Voltage	Max Array Watts	Minute Absorption	Minutes in Float	Time Equalize	Trimetic % Return	Weather Condition
12/11/2020	14.9_14.9	12.7_12.7	25.5_46.6	360_670	69.7_70.8	437_526	210_210	141_141		107	Mostly Cloudy
12/12/2020	15.5_15.5	11.9_11.9	59.4_79.1	860_1140	68.5_69.9	454_569	248_246	0_0	96_96	114 eq to 120	Sun Morning
12/15/2020	16.4_15	11.9_11.9	50.8_75.1	720_1070	69.7_70.9	487_642	205_209	0_0		107	Sunny
12/16/2020	15.5_15.5	12.1_12.1	62.4_106.4	890_1530	24.5_70.5	427_672	246_204	0_0		112	Sunny
12/17/2020	13.8/13.8	11.6_11.6	42.8_63.8	560_850	23.3_70.3	217_347	0_0	0_0		87%	Cloudy
12/18/2020	15.3_15.3	11.6_11.5	85.8_138.2	1190_1930	24.2_70.4	426_658	112_50	0_0		110%	Sunny
12/19/2020	15.3_15.4	11.8_11.8	71.2_107.3	1020_1530	65.9_70.3	427_659	246_247	0_0		120%	Sunny
12/20/2020	15.4_15.4	11.8_11.8	66.2_96.6	940_1400	69.1_70.2	582_642	317_259	0_0		116%	Sunny
12/21/2020	15.4_15.3	11.8_11.7	62_108.6	870_1570	68.3_69.4	613_652	294_243	0_0		112%	Sunny
12/22/2020	15_15	13.1_13.1	22.5_75.8	320_1110	67.3_69.6	626_668	89_152	188_0	Reset controller	118%	Pt Cloudy
12/23/2020	15.3_15.3	11.8_11.7	61.6_114.4	860_1650	70.1_70.6	642_720	259_187	0_0		111%	Pt Cloudy
12/24/2020

BB. · December 2020

Hi Bill, Starting from the paper design side... 5% to 10%-13% rate of charge:

450 AH * 14.5 volts charging * 1/0.77 panel+controller deraring * 0.05 rate of charge = 424 Watt array minimum (backup system/summer/sunny weather usage)
450 AH * 14.5 volts charging * 1/0.77 panel+controller deraring * 0.10 rate of charge = 847 Watt array nominal (full time off grid minimum suggested)
450 AH * 14.5 volts charging * 1/0.77 panel+controller deraring * 0.13 rate of charge = 1,102 Watt array "typical" cost effective maximum

And the minimum array voltage for a 12 volt bank is Vmp~17.5 volts... Minimum voltage for MPPT operation around 19.5 volts Vmp-array. Recommeneded "optimum" array Vmp~30 volts. And Vmp-array-max ~ 100 volts or so (need min-temperature for your location(s).

The Eldora panel is Vmp~17.85 volts per panel and Imp~8.41 amps.

Hytech is Vmp~21.052 volts (seems a bit high) and Imp~9.5 amps.

The controller 1 and controller 2 are reporting Vmp-array near 70 volts... That would seem to indicate that you have 3x panels (?) in series for each. Although, controller 1 indicates a couple days at ~24 volts max voltage... Does not make sense (bad panel/weird connections)?

I don't see how you are reaching those voltages with just 2x panels in series for both controllers... But that configuration (2x sets panels in series on 2x different controllers) is fine for now.

Battery votlage is a bit high... Typically around 14.75 volts @ 75F for absorb charging... >15.x volts is for Equalize charging... Although, it is possible for batteries to exceed 15.x volts for short periods of time as the MPPT controllers sweep to figure out Vmp/Imp for the array (guessing).

Your Trimetric numbers seem to be good... You are typically recharging >=110% (AH?) most every sunny day.

Low battery voltage is pretty low--Unless you have surge loads (typically want to avoid running below ~11.5 volts except for short periods of surge loads--Such as starting a pump/motor). You are pulling 100-200 AH per day (both controllers added together). Typically like to see ~25% for daily loads (0.25*450AH=125 AH per day) to 50% discharge for an RV/heavy loading... It seems to be that you are "using" your battery bank/solar harvest pretty well.

Things to check for... Controller 1 and 2 -- May be identical configuration/arrays--But they will probably not be in "sync"--Minor differences in voltage readings/accuracy of meters could make one go to float sooner/etc... Perfectly OK. The controller with the 'highest' effective charging voltage "wins".

I suggest that each controller be "home run" back to the battery bus ("star" wired--Each controller has its own wiring back to the battery bank). Suggest to not "daisy chain" from controller 1 to 2 to battery bank (one set of cables shared for both controllers to battery bank). Sharing the wiring can cause controllers to confuse each other.

The other thing to make sure... Always connect controllers to battery bank first, then to the (energized) solar array. And disconnect solar first, then battery bank. Some controllers can get "confused" when booted from the solar array first--Or even be damaged.

If you have a voltmeter--Measure the Vpanel and Vbatt terminal voltages of the controllers (under sun, hopefully charging). Would like to double check the Varray and Vbatt voltages at the controllers (you can also measure Vbatt bus at the same time--Vbatt controller and Vbatt bus should be very close).

Your numbers are a bit "erratic" for the solar charge controllers--But they do seem to be work pretty well (and confirmed with the Trimetric).

Your panels (voltage does not make sense)--But if you have 2x series panels on two different TS MPPT 60 controllers, that is fine too.

Checking voltage with a meter at various points (and times of day) to confirm operation... A hydrometer would be nice too (specific gravity)...

Is the system working (producing energy) the way you expect?

-Bill

billdean · December 2020

The controller 1 and controller 2 are reporting Vmp-array near 70 volts... That would seem to indicate that you have 3x panels (?) in series for each. Although, controller 1 indicates a couple days at ~24 volts max voltage... Does not make sense (bad panel/weird connections)?
You are correct 3 panels in series..The 24 volt max voltage days is when I series 2 200w hightec panels and just hooked the 150 Vikram into the combiner box. I believe in that type of installation the control would read the lower voltage panel.

Battery votlage is a bit high... Typically around 14.75 volts @ 75F for absorb charging... >15.x volts is for Equalize charging... Although, it is possible for batteries to exceed 15.x volts for short periods of time as the MPPT controllers sweep to figure out Vmp/Imp for the array (guessing).
I believe this is more about temperature compensation that anything else. My absorption set point is 14.82 volts compensated at .005 v/cell would easily put me over 15 volts on days below 25*c

Low battery voltage is pretty low--Unless you have surge loads (typically want to avoid running below ~11.5 volts except for short periods of surge loads--Such as starting a pump/motor). You are pulling 100-200 AH per day (both controllers added together). Typically like to see ~25% for daily loads (0.25*450AH=125 AH per day) to 50% discharge for an RV/heavy loading... It seems to be that you are "using" your battery bank/solar harvest pretty well.
It would be surge loads......I get up in the morning and have to have a cup of coffee. My coffee pot draws the voltage down but is recovers quickly. I use 20 to 30% of my battery capacity most nights as taken from my trimetric

Things to check for... Controller 1 and 2 -- May be identical configuration/arrays--But they will probably not be in "sync"--Minor differences in voltage readings/accuracy of meters could make one go to float sooner/etc... Perfectly OK. The controller with the 'highest' effective charging voltage "wins".
Interesting

I suggest that each controller be "home run" back to the battery bus ("star" wired--Each controller has its own wiring back to the battery bank). Suggest to not "daisy chain" from controller 1 to 2 to battery bank (one set of cables shared for both controllers to battery bank). Sharing the wiring can cause controllers to confuse each other.
Well Bill.......This may be some of my problem! As it stands now I do have one set of cables running to the battery bank. This is an easy fix I hope. The reason I have done this is the lack of termination space on the battery terminals. I will look at this today and try and make changes.

Your numbers are a bit "erratic" for the solar charge controllers--But they do seem to be work pretty well (and confirmed with the Trimetric).
I have made a lot of adjustments to the wiring of the combiner box to try and get the best output to the batteries. This would explain why the numbers are so erratic. I will get a weeks worth of data before I make any more changes

Your panels (voltage does not make sense)--But if you have 2x series panels on two different TS MPPT 60 controllers, that is fine too.
At present I have taken the odd 150 volt panel out of the mixture. I am running with 3 hightec panels in series to controller #1 and 2 hightec panels to controller #2. I will keep it this way for sometime to gain some logging data.

Is the system working (producing energy) the way you expect?

The system is working fairly well considering the shorten days. It does get back to 100% charge most everyday. The specific gravity is a little bit different in the cells on a daily basis I would like to see the trimetric return a bit more "return percentages" maybe 115% to 120% daily. I have been working a little on the temperature compensation to accomplish this. I do equalize about once every couple of months. For the most part I am happy with it. I believe I will leave that odd ball panel off. If I ever think I need more wattage I will get a another Hightec panel. Too many variables mixing different panels.
Thanks Bill for all this information!! Merry Christmas!

Different Solar Panels

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