FM80 Current Limit set to 77 yet caught it at 79+

Discussion about the FM100, FM80, and FM60 Charge Controllers

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Yoe
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My RE system: Flexpower One: VFXR3524, (2) FM80, MATE3s, FlexNetDC

REC310pv72 310 watt panels (4 strings @ 3 series, 2 strings per FM80)

FM80 Current Limit set to 77 yet caught it at 79+

Post by Yoe » Wed Feb 19, 2020 2:12 pm

I have a FP1 VFXR3524A system with 2 FM80's. Both FM80's have Current Limit set to 77 amps yet I caught one at 79.1 amps and shortly later the OutBack Ground Fault Detector-GFDI-80D tripped. I had the FM80's set to 77 amps because the GFDI-80D tripped earlier. I figured I wouldn't have to limit the current at all.

What could I be missing?

raysun
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My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
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Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: FM80 Current Limit set to 77 yet caught it at 79+

Post by raysun » Wed Feb 19, 2020 2:43 pm

The FM charge controllers don't seem to have "hard" current limiters, and seemingly can exceed their maximum rated current when the input is overdriven. The reaction time to limit current seems to be a function of recalculating (MPPT perhaps) and has a definite time lag under certain circumstances.

The two current limits: on the charge controller, and global charge limit set on the Mate, also seem to be impacted by a delay. The charge controller limit seems to be the "faster" of the two.

A few things I've found by experiment:

• Don't overdrive the input past its rated power.
• Leave some "headroom" in the current limit below the breaker rating.
• Use the local charge controller limit setting rather than the global setting.

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IanMcCluskey
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Re: FM80 Current Limit set to 77 yet caught it at 79+

Post by IanMcCluskey » Wed Feb 19, 2020 3:32 pm

Raysun is correct about the FM60 and the FM80.

Fortunately, the FM100 does not have this issue! Even tested to failure, it will limit current to no more than 100.5 amps output, including margin of error.

When installed with 7,000 W of PV or less, under warranty, it never exceeds 100.1 amps.
Ian McCluskey
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Alpha Technologies Inc. / OutBack Power Technologies
3767 Alpha Way Bellingham WA 98226 USA
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raysun
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My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: FM80 Current Limit set to 77 yet caught it at 79+

Post by raysun » Wed Feb 19, 2020 11:02 pm

X2 price for X1.2 output capacity. OK, a good chunk of it goes to bullet-proofing, and another chunk into increased power dynamic range - thats cool.

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IanMcCluskey
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Re: FM80 Current Limit set to 77 yet caught it at 79+

Post by IanMcCluskey » Thu Feb 20, 2020 8:17 am

And built in arc-fault detection and interruption, which can cost on the order of $1000 for an external device.
+ compatibility with multiple module-level rapid shutdown options
+ improved MPPT
Ian McCluskey
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Alpha Technologies Inc. / OutBack Power Technologies
3767 Alpha Way Bellingham WA 98226 USA
http://www.alpha.com

raysun
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Posts: 3019
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: FM80 Current Limit set to 77 yet caught it at 79+

Post by raysun » Thu Feb 20, 2020 9:03 am

IanMcCluskey wrote:
Thu Feb 20, 2020 8:17 am
And built in arc-fault detection and interruption, which can cost on the order of $1000 for an external device.
+ compatibility with multiple module-level rapid shutdown options
+ improved MPPT
Definitely the charge controller to get for a modern, code-compliant system.
Last edited by raysun on Thu Feb 20, 2020 9:59 am, edited 1 time in total.

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IanMcCluskey
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Re: FM80 Current Limit set to 77 yet caught it at 79+

Post by IanMcCluskey » Thu Feb 20, 2020 9:46 am

Indeed, the world most installers live in these days.
Ian McCluskey
Product Manager


Alpha Technologies Inc. / OutBack Power Technologies
3767 Alpha Way Bellingham WA 98226 USA
http://www.alpha.com

raysun
Forum Emperor
Posts: 3019
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: FM80 Current Limit set to 77 yet caught it at 79+

Post by raysun » Thu Feb 20, 2020 10:05 am

IanMcCluskey wrote:
Thu Feb 20, 2020 9:46 am
Indeed, the world most installers live in these days.
Out here in the Wild West, there's a lot of "don't ask, don't tell". As a consequence, the local fire department won't touch a house fire if solar panels are installed.

Having safe equipment is here, as everywhere, the first and best line of defense.

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