FM80 dropout at end of absorb

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provo
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My RE system: Sixteen Evergreen EC-120
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Location: Sierra foothills

FM80 dropout at end of absorb

Post by provo » Sun Jun 28, 2020 10:49 am

A strange thing happened yesterday as absorb ended and float began. I had dropped the grid feeding through the FXR with about 1h remaining on a 3h absorb, after verifying that the FM would be able to take over the absorb and loads. I assumed absorb would terminate after 3h and float would begin as usual, with the FM holding float and continuing to handle all the loads as usual, like this:

Typical.jpg

Instead I noticed (much later!) that when absorb had finished, the FM had gotten stuck in the “charged” state rather than going into float, and also didn’t provide any output to run loads. I turned on the grid input and the charger and did a Start Bulk, which woke up the FM for charging and also started the FXR charging and covering loads. Notice the gap in PV production in the 2:00p - 3:00p period:

PV Dropout.jpg

Why did the FM get hung up in the “charged” state rather than smoothly transitioning into float and continuing to cover loads as it usually does?

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EA6LE-ONE
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Re: FM80 dropout at end of absorb

Post by EA6LE-ONE » Sun Jun 28, 2020 11:02 am

Do you have the absorb on FXR 0.4V smaller than on FM? to give priority to sun generation the absorb voltage should be smaller on inverters than on CCs Also calibrate the inverter DC voltage when is getting in absorb.

provo
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Posts: 403
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Location: Sierra foothills

Re: FM80 dropout at end of absorb

Post by provo » Sun Jun 28, 2020 11:09 am

EA6LE-ONE wrote:
Sun Jun 28, 2020 11:02 am
Do you have the absorb on FXR 0.4V smaller than on FM? to give priority to sun generation the absorb voltage should be smaller on inverters than on CCs Also calibrate the inverter DC voltage when is getting in absorb.
I have a 24V system, so the FXR is set 0.2V lower, yes. The first image shows everything working properly and was only one day earlier with no changes since then. Maybe the FM had a glitch?

raysun
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Hyundai 355 watt panels (6 - 3 strings of 2 in series)
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Re: FM80 dropout at end of absorb

Post by raysun » Sun Jun 28, 2020 1:39 pm

provo wrote:
Sun Jun 28, 2020 11:09 am
EA6LE-ONE wrote:
Sun Jun 28, 2020 11:02 am
Do you have the absorb on FXR 0.4V smaller than on FM? to give priority to sun generation the absorb voltage should be smaller on inverters than on CCs Also calibrate the inverter DC voltage when is getting in absorb.
I have a 24V system, so the FXR is set 0.2V lower, yes. The first image shows everything working properly and was only one day earlier with no changes since then. Maybe the FM had a glitch?
The FM, as you expect, will remain in Float until the sun goes down, unless it thinks it has nothing to do because the battery voltage is above it's set Float voltage.

Some temporary situation perhaps? If so, what?

provo
Forum Guru
Posts: 403
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Location: Sierra foothills

Re: FM80 dropout at end of absorb

Post by provo » Sun Jun 28, 2020 2:03 pm

raysun wrote:
Sun Jun 28, 2020 1:39 pm

The FM, as you expect, will remain in Float until the sun goes down, unless it thinks it has nothing to do because the battery voltage is above it's set Float voltage.

Some temporary situation perhaps? If so, what?
That's a mystery! The only unusual factors yesterday were the heat (not that bad for around here, but the hottest yet this year), the battery temps. (pushing 95°F), and the high (for me) loads. I think at one point the A/C compressor was running (570W) at the same time as the fridge defrost cycle (400W). But the FM was putting out 1240W, so it shouldn't have been a strain.

By the time the FM got stuck in "charged" the charger had been off (FXR inverting only) for an hour. A gremlin? I'll be watching for a similar occurrence....

provo
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Posts: 403
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Location: Sierra foothills

Re: FM80 dropout at end of absorb

Post by provo » Sun Jun 28, 2020 2:46 pm

The plot thickens.....absorb recently finished and float has been going for 30m on FM alone -- no grid use at all today. I'm used to float holding a voltage somewhat less (26.5V now) than my set point (27.0V) on a warm day. That part is right, but I'm also used to float pushing around 0.5A into the battery. Ever since float started, both the FNDC and the Trimetric say 0.6A - 2.7A are being pulled OUT of the battery even though the FM claims to be floating.

The bigger the load, the more negative the shunt indicates. And the battery agrees -- its voltage drops (26.3 with the A/C on) and the SOC drops also, to 99%. The FM puts out more to cover larger loads, but never enough to get a positive current into the battery like it used to during float.

Is my FM dying?

raysun
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My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
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Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: FM80 dropout at end of absorb

Post by raysun » Sun Jun 28, 2020 3:31 pm

provo wrote:
Sun Jun 28, 2020 2:46 pm
The plot thickens.....absorb recently finished and float has been going for 30m on FM alone -- no grid use at all today. I'm used to float holding a voltage somewhat less (26.5V now) than my set point (27.0V) on a warm day. That part is right, but I'm also used to float pushing around 0.5A into the battery. Ever since float started, both the FNDC and the Trimetric say 0.6A - 2.7A are being pulled OUT of the battery even though the FM claims to be floating.

The bigger the load, the more negative the shunt indicates. And the battery agrees -- its voltage drops (26.3 with the A/C on) and the SOC drops also, to 99%. The FM puts out more to cover larger loads, but never enough to get a positive current into the battery like it used to during float.

Is my FM dying?
I wonder if the voltage calibration is off. Can you measure the voltage at the battery terminals, the BAT +/- at the FM80 terminals and compare to the OUT Volt reading on the display? All three should agree.

provo
Forum Guru
Posts: 403
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Location: Sierra foothills

Re: FM80 dropout at end of absorb

Post by provo » Sun Jun 28, 2020 3:50 pm

raysun wrote:
Sun Jun 28, 2020 3:31 pm

I wonder if the voltage calibration is off. Can you measure the voltage at the battery terminals, the BAT +/- at the FM80 terminals and compare to the OUT Volt reading on the display? All three should agree.
I'll check again, but I believe the agreement is good when not much current is going anywhere, and gets worse at larger currents, either into or out of the battery. I'll get some fresh measurements.

provo
Forum Guru
Posts: 403
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Location: Sierra foothills

Re: FM80 dropout at end of absorb

Post by provo » Mon Jun 29, 2020 12:35 pm

raysun wrote:
Sun Jun 28, 2020 3:31 pm

I wonder if the voltage calibration is off. Can you measure the voltage at the battery terminals, the BAT +/- at the FM80 terminals and compare to the OUT Volt reading on the display? All three should agree.
Here's what I saw this morning:

Voltages (early) at no net current in or out of the batteries:

battery terminals..........25.34
FM Batt terminals..........25.37
FM display Vout.............25.2
FNDC Batt Volts.............25.2


Voltages (later) at 34A charging from FM:

battery terminals..........28.26
FM Batt terminals..........28.49
FM display Vout.............28.4
FNDC Batt Volts.............28.2

Seems reasonably well calibrated...

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