can array be bigger than charge controller

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can array be bigger than charge controller

Postby mr green on Mon Mar 06, 2017 5:38 pm

Hi
I have a outback flexmax 60 amp charge controller and have four 260 watts 24 volts panels and think 11 amps each
can I add more panels , say another two 260 watts panels, which would bring me over the 60 amps, and on cloudy days would help ,but don't want to damage the controller
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Re: can array be bigger than charge controller

Postby Mike Curran on Mon Mar 06, 2017 7:47 pm

mr green, check out Outback's string sizing tool: http://www.outbackpower.com/outback-sup ... izing-tool
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Re: can array be bigger than charge controller

Postby fred2258 on Mon Mar 20, 2017 6:20 am

Mike Curran wrote:mr green, check out Outback's string sizing tool: http://www.outbackpower.com/outback-sup ... izing-tool


This didn't answer the question. Mr Green asked if it would hurt the controller to have an array with more than the recommended watts. I am wondering this also. If the controller just doesn't use the extra watts on sunny days, but can use them on less than ideal days, this would make sense. So again what would happen if the wattage of the array was higher than the max rating of the controller?
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Re: can array be bigger than charge controller

Postby Mike Curran on Mon Mar 20, 2017 8:44 am

The manual says don't exceed 150VDC input or you'll damage the FM60, but doesn't address operating with array wattage exceeding OB's recommended 1600 watts. My guess would be the FM60 would limit output current to 60A, with possibly no ill effects, but someone from Outback would have to answer that.

Not helpful, I know :neutral:
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Re: can array be bigger than charge controller

Postby jguzman on Mon Mar 20, 2017 12:18 pm

For best practice the array should be 15% less than the maximum rating listed. Multiply the maximum rating by .85 to determine best array size for your battery bank/controller setup. Downsizing the array from the maximum rating allows for longer controller life, greater efficiency, and reduces the chance of nuisance breaker tripping. Multiple controllers can be paralleled on the same battery bank to meet system charging needs/handle all the PV power.

Technically speaking the controller will "soft limit" the output down to it's rated output ie. 80A for an FM80 controller, however this can cause the output battery breaker to trip since it can react faster than the limiting feature specially under low battery conditions. It will also work it's inner components harder and may fall outside the manufacture standard warranty.

For further reading check out this Application note:
http://outbackpower.com/downloads/docum ... p_note.pdf
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Re: can array be bigger than charge controller

Postby SandyP on Mon Mar 20, 2017 4:09 pm

mr green wrote:Hi
I have a outback flexmax 60 amp charge controller and have four 260 watts 24 volts panels and think 11 amps each
can I add more panels , say another two 260 watts panels, which would bring me over the 60 amps, and on cloudy days would help ,but don't want to damage the controller


Are the figures you are quoting at the panels rated SOC or the higher STC?

One way around maximizing solar input over a day without exceeding the CC amp limit is to have a larger solar panel array split with some panels facing east and some west. This will lower the maximum midday panel output but give you better panel output in the morning and afternoon.
With more panels you will still get more panel output with the split array on a cloudy day.
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Re: can array be bigger than charge controller

Postby mr green on Tue Mar 21, 2017 5:17 pm

thanks Sandy
I have installed 3 panels facing south and two panel at the west , so they are at 90 degree to each other
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Re: can array be bigger than charge controller

Postby SandyP on Tue Mar 21, 2017 6:38 pm

mr green wrote:thanks Sandy
I have installed 3 panels facing south and two panel at the west , so they are at 90 degree to each other


Your MyRE System info shows you have a 12V battery system - is this correct?

If so, with your initial 4 x 260W panels and de-rating these by 25% the CC on a 12V system would probably have already seen charging amps above 60A. Unless you re-orient your initial 4 panels you will have issues with extra panels.

With an additional 2 x 260W panels,even facing west, you will definitely see your CC charging amps exceed 60A.

It is the battery voltage and the panel Watts that are used to calculate the potential maximum CC output amps not the panel Volts or panel amps. Outback recommends a maximum 800W of panels for a 12V system using an FM60.
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Re: can array be bigger than charge controller

Postby fred2258 on Wed Mar 22, 2017 5:44 am

jguzman wrote:
Technically speaking the controller will "soft limit" the output down to it's rated output ie. 80A for an FM80 controller, however this can cause the output battery breaker to trip since it can react faster than the limiting feature specially under low battery conditions. It will also work it's inner components harder and may fall outside the manufacture standard warranty.

For further reading check out this Application note:
http://outbackpower.com/downloads/docum ... p_note.pdf


So... What happens if you limit the output? Like on a system I was going to install; 6 - Aquion 48 volt batteries, 20 REC 255 Watt modules (REC255PE). and 2 - FM80s. I would have had to limit the output of the FM80s to 120 amps for the batteries. Where does the extra power go, or would I have had to install less modules?
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Re: can array be bigger than charge controller

Postby EMCF on Wed Mar 22, 2017 4:36 pm

If the input PV voltage is below 150VDC, there will be no harm to the charge controller even if the PV system wattage exceeds the designed PV kw input, (at least in theory). Think of it as potential energy, the PV array has so much to offer but is being limited by the designed max charging current, which is 60A for FM60 and 80A for FM80. Yes, there will be wasted energy when this situation takes place, but theoretically, this energy stayed in the PV array and did not really reached the batteries.
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Re: can array be bigger than charge controller

Postby mr green on Wed Mar 22, 2017 6:10 pm

yes it is a 12volt system
I did put a breaker on both set of panels, one set with 3 - 260watts each for a total of 780 total and the other set at 2 - 260 watts panels total 520 watts, I as thinking of shutting off the set of 2 panels and only use them on cloudy days or if sun only come out in late afternoon.
what I did notice is when batteries were charging in the morning the amps was up to 40 amps but did drop to 10 amps once the batteries were charged even with all 5 panels on , it seems like the charge controller will only seed the amps the batteries need ,no matter how many panels are connected, is this correct
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Re: can array be bigger than charge controller

Postby blackswan555 on Thu Mar 23, 2017 1:46 am

I did notice is when batteries were charging in the morning the amps was up to 40 amps but did drop to 10 amps once the batteries were charged even with all 5 panels on , it seems like the charge controller will only seed the amps the batteries need ,no matter how many panels are connected, is this correct


Yes, Correct & what you describe above is "normal" charging.
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
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Re: can array be bigger than charge controller

Postby SandyP on Thu Mar 23, 2017 2:00 am

mr green wrote:thanks Sandy
I have installed 3 panels facing south and two panel at the west , so they are at 90 degree to each other


Sorry, I misread your post and thought you had retained your original 4 panel array and would add another 2 panels.
With a 3 panel array and another 2 facing west and using the breaker to limit the maximum panel input then you should be OK.
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Re: can array be bigger than charge controller

Postby blackswan555 on Thu Mar 23, 2017 4:56 am

From aplication note above, Notice the bit in bold,,
One other option does exist for site owners that have already installed their PV array where it would be
difficult or prohibitively expensive to rewire the array and add another charge controller. The solution
involves moving the OutBack 80A GFDI output breaker from the output of the charge controller to the
input side, and putting in 100A circuit breakers on the output. Additionally, with the GFDI on the input
side of the charge controller, there must be a separate disconnecting means between the combiner box
and the charge controller other than the GFDI, such as on the output of the combiner box. Otherwise,
opening the GFDI on the input side will “unground” the array which is not allowed by the NEC.
Putting 100A circuit breakers on the output of the FM80 may also require replacing the conductors
between the output of the charge controller and the DC bus or battery bank with 100A conductors. The
FM80 has its own internal current limit protection of 80A so the 100A external circuit breakers are really
there to protect the conductors, not the charge controller.

An electrical diagram of the 80A GFDI on the output of the charge controller as recommended for most
applications is shown below in Figure 1
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
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