lower solar input on sunny vs cloudy day

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LibbyLou
Forum Member
Posts: 6
Joined: Thu Oct 20, 2022 1:55 pm
My RE system: 24v system
Eight 160-watt each solar panels are wired in series and parallel config.
Four 12v AGM MK Batteries 8A8D 250 Amp 100 hour
Outback FlexMax 60
Mate 2
3000-watt Go Power Inverter with Xantrex remote and Link10

lower solar input on sunny vs cloudy day

Post by LibbyLou »

Recently installed Outback FlexMax 60 with Mate 2.
On completely overcast days pulled up to 41 amps
On full sun just hitting 31 amps.
My Solar installer did a basic setting free of charge, did not go into Advanced settings, and wanted to hear results on a sunny day vs cloudy. But is out of town at the moment. Thus I am using my Gen to charge up, more than with my PMW

My system setup
24 volt configuration
Eight 160 watt solar panels. wired in series and parallel
Four 8A8D 12 AGM 250 amp 100 hour
Go Power 3000 watt inverter with Xantrex remote and Link10

I think the batteries are wired like the panels

Thx, LibbyLou
raysun
Forum Emperor
Posts: 9024
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: lower solar input on sunny vs cloudy day

Post by raysun »

Not quite sure what to make of this. I assume the amp readings are from the FM60 front panel? Are they IN Amps (from solar array) or OUT Amps (to battery)?

FWIW, if the FM60 is the only Outback equipment in the system, the Mate isn't strictly necessary. Why was it installed?
LibbyLou
Forum Member
Posts: 6
Joined: Thu Oct 20, 2022 1:55 pm
My RE system: 24v system
Eight 160-watt each solar panels are wired in series and parallel config.
Four 12v AGM MK Batteries 8A8D 250 Amp 100 hour
Outback FlexMax 60
Mate 2
3000-watt Go Power Inverter with Xantrex remote and Link10

Re: lower solar input on sunny vs cloudy day

Post by LibbyLou »

in AMPs from solar.
raysun
Forum Emperor
Posts: 9024
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: lower solar input on sunny vs cloudy day

Post by raysun »

LibbyLou wrote: Thu Oct 27, 2022 3:29 pm in AMPs from solar.
OK. There's several variables that determine the charge controller's IN Amps.
The first and foremost is the solar array. A typical 160W solar panel has an open circuit voltage of about 20V, so would need to be arrayed 2 in series at minimum. With the FM60, 8 160W panels could be arrayed 2 parallel strings of 4 in series, or 4 parallel strings of 2 in series. Either would work. The 1280W rated output is within the controllers maximum rating for a 24V battery. If configured as above, the FM60 should operate properly with the correct basic parameter values for the battery type deployed. To confirm the above, it would be good for you to provide the solar panel model so the specs can be cross-referenced.
So why the unexpected behavior? The answer isn't evident from the information at hand, but there's a couple possibilities.
The first is related to panel physical behavior as relates to sunlight exposure. Our subjective estimation of solar energy reaching the panels in certain overcast conditions can be surprisingly off the mark. Likewise, our assumption that solar panels produce maximal output in clear, sunny conditions is also misleading. In both cases, the panels' behavior is influenced by more than photons striking silicon. Heat plays a big role. The hotter the solar panel, the lower its efficiency at converting sunlight to electrical current. The Standard Test Conditions (STC) at which solar panels are measured and rated, call for an ambient temperature of 77°F. On a sunny day, the panels can heat up considerably higher than that. Conversion losses can easily reach 25%-40%. It wouldn't be out of the ordinary for "full output" from a panel to be lower than its rating. Even more of a suprise, when the panels are cooler than STC, the conversion efficiency can be higher than rated, and in such conditions as high overcast with cool air temperatures solar arrays may perform better than expected. All that being said, it would be unlikely an array would consistently put out higher current on an overcast day relative to a sunny day.

Question: Were the IN Amps readings in the original post "one off" samples, or indicative of a consistent pattern of behavior? Did you see this once, or do you see it all the time?

A more likely reason for the seeming variation of IN Amps has to do with the battery charge cycle. The charger follows a multi-stage charge profile that will vary demand for charging current depending on the battery's state of charge, and on the charger's programming. The charging cycle follows a predictable pattern through its 3 stages: Bulk stage - in this first stage, the charger "wakes up" after sunrise, and feeds as much current to the battery as is available from the solar array; Absorb stage - when the battery fills, its voltage rises and reaches a point (at about 80% State of charge) where the charger's programmed Absorb Voltage is reached, and the charger switches to constant voltage mode which feeds a steadily declining charge current to the battery which in turn demands less current from the solar array; Float stage - when Bulk and Absorb phases have completed, the charger switches to a lower constant voltage, "floating" the battery at a steady state of charge where the current drawn from the solar array varies by the amount of current drawn from the battery by the loads. In all the above charging cycle, the demand for current is constantly changing. Performance of the system through the charge cycle requires analyzing the data for accumulated energy delivered to the battery. This is a value measured over time. Instead of looking at instantaneous Amps (e.g. IN Amps) it's more informative to look at the total daily Watt Hours fed to the battery. The FM60 logs this daily as kWH (kilowatt hours) and stores over 200 days of data. The log can be read on the FM60 screen by stepping through the daily entries using the menu system and front panel buttons.

The final piece of the puzzle is the charger values programmed into the FM60. They must be set properly for the battery type and capacity in accordance with the battery manufacturers specifications.
Question: Is the battery model the 8A8DLTP-DEKA brand? Is it another model/brand? Please list.

Finally, did your installer give you a listing of the charging parameters that were entered into the FM60?
LibbyLou
Forum Member
Posts: 6
Joined: Thu Oct 20, 2022 1:55 pm
My RE system: 24v system
Eight 160-watt each solar panels are wired in series and parallel config.
Four 12v AGM MK Batteries 8A8D 250 Amp 100 hour
Outback FlexMax 60
Mate 2
3000-watt Go Power Inverter with Xantrex remote and Link10

Re: lower solar input on sunny vs cloudy day

Post by LibbyLou »

wow thanks for the time you have taken, I am still reading it over again and will respond further.
raysun
Forum Emperor
Posts: 9024
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: lower solar input on sunny vs cloudy day

Post by raysun »

LibbyLou wrote: Thu Oct 27, 2022 10:56 pm wow thanks for the time you have taken, I am still reading it over again and will respond further.
There's a lot to unpack. Maybe more in the vein of asking the time, and getting told how to build a clock. 😉
If you can get info for the Questions: a clearer answer can be forthcoming.
LMK if u have ?
LibbyLou
Forum Member
Posts: 6
Joined: Thu Oct 20, 2022 1:55 pm
My RE system: 24v system
Eight 160-watt each solar panels are wired in series and parallel config.
Four 12v AGM MK Batteries 8A8D 250 Amp 100 hour
Outback FlexMax 60
Mate 2
3000-watt Go Power Inverter with Xantrex remote and Link10

Re: lower solar input on sunny vs cloudy day

Post by LibbyLou »

Please excuse my absence, I have a family medical matter I am currently dealing with. I really appreciate the time taken and the wealth of information shared.

These are “IN” amps from solar array on CC itself and on Mate
The CC is deep in basement of bus, the Mate is for easy access.

Batteries: Four (4) MK brand AGM 12 volt, rated 250 amps each (100hr) in 24 volt config. = 500 amp battery bank.
never go below 50% discharge, thus max 250 amps ever available. In reality 220 AMPs due to age of bank

Eight (8) GoPower 160 watt Solar Panels – 2 in series, four in parallel.

Charge Controller settings
Absorb 28.4
Float 27.2
Snooze: 0.6 amp
Wake up mode: VOC change
Wake up mode: 1.5v. Time 5 min

MPPT mode: Auto Track (did switch this setting back and forth several times. AMPs briefly jumped from 31 amps to 43amps, but quickly back to 31 amps once setting completed.)

Grid Tie: Non GT
Park: MPP 90%
MPP Range Limit % voc: minimum ½
MPP Range Limit % voc: Maximum 90%
Absorb time: 3 hours
Absorb End AMPs: 0A

Rebulk Voltage: 24.0 vdc (does the setting mean batteries are drained to half before charging begins?)

V Batt Calibration 27.2vdc
RTS Compensation: Wide
RTS Compensation: Upper limit 28.2vdc
RTS Compensation: Lower limit 26.4vdc
Auto Restart: Mode 0
AUX output polarity: Active High

I recently went through the logs and realized that something occurred when I moved my rig.
I spent a few days right after install in the same location which was overcast
After I relocated I was in sunny weather and noted the amperage intake drop.
Keep in mind I was plugged in at the same time the first couple days as well, then was boondocking after that.




.
raysun
Forum Emperor
Posts: 9024
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: lower solar input on sunny vs cloudy day

Post by raysun »

Batteries: Four (4) MK brand AGM 12 volt, rated 250 amps each (100hr) in 24 volt config. = 500 amp battery bank.
never go below 50% discharge, thus max 250 amps ever available. In reality 220 AMPs due to age of bank
MK/DEKA/East Penn Battery is a large domestic manufacturer. The battery that appears to meet the above spec is the 8A8DLTP-DEKA 12V AGM.

A fine point. Battery capacity is measured in Amp Hours (AH), so the battery blocks are rated 250AH at 100 Hour rate of discharge. Typically, the 20 Hour rare is used for capacity calculations, so 245AH when new. Judging capacity as a battery ages is a bit of a black art. Is there a battery monitor on the system?
Charge Controller settings
Absorb 28.4
Float 27.2
Snooze: 0.6 amp
Wake up mode: VOC change
Wake up mode: 1.5v. Time 5 min

MPPT mode: Auto Track (did switch this setting back and forth several times. AMPs briefly jumped from 31 amps to 43amps, but quickly back to 31 amps once setting completed.)

Grid Tie: Non GT
Park: MPP 90%
MPP Range Limit % voc: minimum ½
MPP Range Limit % voc: Maximum 90%
Absorb time: 3 hours
Absorb End AMPs: 0A
Absorb voltage is about middle of the specified range.
Float voltage is a bit high, if in a warm locale. 27.1V might be better.
The other settings can be left alone. (Exception - Absorb Time. More on this in a bit.)
Rebulk Voltage: 24.0 vdc (does the setting mean batteries are drained to half before charging begins?)
Using voltage to estimate battery state of charge (SoC) is a tricky proposition, especially under load. Rebulk Voltage is the point at which the charge controller would start a new charge cycle. However, once a charge cycle completes, the charger goes into Float until the sun goes down. If there's not enough solar energy to maintain float, the charger drops into bulk in any event. Also, when the charge controller "wakes up" in the morning, it automatically starts a new charge cycle irrespective of battery voltage.
V Batt Calibration 27.2vdc
RTS Compensation: Wide
RTS Compensation: Upper limit 28.2vdc
RTS Compensation: Lower limit 26.4vdc
Auto Restart: Mode 0
AUX output polarity: Active High
VBATT Calibration is used to calibrate the charge controller's internal voltmeter to the actual battery voltage as measured at the controller's BAT +/- terminals with an accurate external voltmeter. VBATT has a range of +0 5 to -0.5V. Leave it set at 0V (center) unless actually calibrating the FlexMax: viewtopic.php?t=15400

RTS (Remote Temperature Sense) uses an optional RTS cable connected to the FlexMax and attached to the battery. It enables Temperature Compensated Charging. (Useful for temperature sensitive batteries like AGM Lead Acid.)
raysun
Forum Emperor
Posts: 9024
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: lower solar input on sunny vs cloudy day

Post by raysun »

I don't see anything in the settings or system description that would account for the behavior described in the OP.
The most plausible guess is the charging current was being observed during the Bulk phase during those cloudy days, and the Absorb phase the sunny days.
During Bulk, the charger sends the maximum current to the battery. During Absorb, the charger maintains a constant voltage, and the charge current steadily declines.
On a sunny day, its likely the Bulk phase us relatively short, with the battery rapidly reaching Absorb Voltage. The 3 hour Absorb Time is a long window for the Absorb Phase, and 8f charging was observed within that window, the charge current would be relatively lower than in Bulk.
The Float phase would be similar to Absorb, but at a lower voltage and current yet again.
When checking, note the charge phase: Bulk, Absorb, Float.
LibbyLou
Forum Member
Posts: 6
Joined: Thu Oct 20, 2022 1:55 pm
My RE system: 24v system
Eight 160-watt each solar panels are wired in series and parallel config.
Four 12v AGM MK Batteries 8A8D 250 Amp 100 hour
Outback FlexMax 60
Mate 2
3000-watt Go Power Inverter with Xantrex remote and Link10

Re: lower solar input on sunny vs cloudy day

Post by LibbyLou »

Raysun, I have something stupid to admit. Those cloudy days.... so embarrassing...I forgot I was plugged in! I just remembered today. I am still having issues, hopefully, after you have had a nice eye roll and perhaps slapped your palm against your forehead, you will stick with me.

but....I am boondocking today at the beach, its very overcast. 8am 36 amp in, bulk. I will monitor it for bulk, absorb, float.

I have had my solar set up for several years, so I am comparing the performance of the Outback Flexmax 60 to my old Trace PWM. The PWM charged up my battery bank much more than the Flexmax 60 has thus far. So what one expects to gain by switching out a PWM to MPPT has so far been a dud. On average, during peak time the PWM pulled in 41amps...maybe irrelevant after your thorough explanation. However I ran my gen 3 or so hours before, now I am needing to run the gen a lot more. Comparing it in the same location, time of year, etc... Again really appreciate this thoughtful and educational information, its great! And I obviously need an education here.

Battery monitor. Xantrex Link
I run my gen in the morning, and on average I use 160 to 190 amps overnight (running oxygen concentrator etc...) I just recently noticed the monitor on two occasions will state, for example, that I am down 60 amps, I turn off the gen to allow my solar to charge the rest, a few minutes later the reading is zero or a positive 1 amps. So possible my monitor occasionally is giving a false picture.

I have an RTS installed.

The battery bank is old, but still going. My alarm goes off around 220, couple of years ago it went off at 250 but it's rare for me to push it beyond 190.

Float Voltage: Climate,- Currently High desert, winter dips to 30 degrees, day 50-60s. But mostly stay in warmer climates.

Rebulk Voltage: understand what you have explained. Thx.
VBatt: to clarify, suggest "zero" setting correct? Ideally hardware setting, but I think I won't take the plunge yet, as I am not as focused as I need to be. I am
my partner's caregiver and get very little sleep. But it would not be a task I would normally shy from.

Absorb time: what about setting it too 2 hours? or less/more?
My other to do is to pull the fuses and test one fuse at a time to see if there is an issue with the panels. though they are only 5 yrs old. Fuses themselves are all good from what I can tell.

I will pay attention to the charge phases and make notes.

Thank you!
raysun
Forum Emperor
Posts: 9024
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: lower solar input on sunny vs cloudy day

Post by raysun »

Absorb time: what about setting it too 2 hours? or less/more?
Absorb Time is a bit complex, and a fixed timer is always a compromise. I didn't see a time recommendation from the manufacturer, however a formula was provided.
Screenshot_20221107-073257.jpg
The recommendation is to Absorb (Constant voltage) charge until the change in charge current is less than 0.1A in an hour. That's a pretty difficult metric to "babysit". I'd use a 3% of C20 capacity rating as termination. When the Absorb current declines to about 12 - 14A, the battery should be fully charged.
LibbyLou
Forum Member
Posts: 6
Joined: Thu Oct 20, 2022 1:55 pm
My RE system: 24v system
Eight 160-watt each solar panels are wired in series and parallel config.
Four 12v AGM MK Batteries 8A8D 250 Amp 100 hour
Outback FlexMax 60
Mate 2
3000-watt Go Power Inverter with Xantrex remote and Link10

Re: lower solar input on sunny vs cloudy day

Post by LibbyLou »

thank you for finding that chart.
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