MPP Maximum

Discussion about the FM100, FM80, and FM60 Charge Controllers

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alaskan
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MPP Maximum

Post by alaskan » Wed Mar 02, 2016 10:42 pm

Have a question on my FM80. What is the "MPP Maximum" setting? Is the number a max percentage? A max Vdc? If I set it to 99, does that mean it operates at max 99% output, or it can take a max 90 Vdc in? Or something else entirely????

Thanks.

SandyP
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My RE system: 8 x 190W 24V Suntech panels (4 strings of 2) July 2011
4 x 325W 24V Suntech panels (2 strings of 2) added Sept2018
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Outback FM60 MPPT (max output lowered to 55amps)
12 x 2V Hoppecke GEL 660 Ah C100 - 24V System
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Re: MPP Maximum

Post by SandyP » Fri Mar 04, 2016 12:52 am

Cannot give much guidance other than what is on Page 48 of the manual :

The Mpp Range Limit % Voc adjusts the upper Mpp limit of
the VOC. The default Charge Controller MPP voltage limit
is set at 90% of the VOC and is normally left alone for an
array. Setting min to 1/2 reduces the initial tracking time
on a high input voltage array and also tracks one-half the
VOC voltage.

The MPP adjustable Charge Controller limits are 80%,
85%, 90%, and 99% of the VOC. The min range limit setting
may be set to FULL if something other than a PV
array is connected to the input of the Charge Controller,
such as a micro-hydro generator (see page 58), but
the VOC cannot exceed 150 VDC at any time. Press the
<min> or <max> soft key to adjust the MPP range limit.

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tallgirl
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Re: MPP Maximum

Post by tallgirl » Sun Mar 06, 2016 4:56 am

alaskan wrote:Have a question on my FM80. What is the "MPP Maximum" setting? Is the number a max percentage? A max Vdc? If I set it to 99, does that mean it operates at max 99% output, or it can take a max 90 Vdc in? Or something else entirely????

Thanks.
It's the upper limit on the sweep voltage, as a percentage of the highest open-circuit (no load) voltage for the array since the last sweep. For most solar arrays the actual MPP voltage is around 75-80% of the open circuit voltage. Using a narrower range on a PV array will reduce the time the charge controller requires to find the correct voltage.

However, unless you know the actual ratio of Vmpp to Voc, selecting 90% (which I think is the default) is fine.
Julie in Texas

I ride bicycles. A lot.

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