Low Battery Cut-Off with FNDC

An area for discussing the OutBack FLEXnet DC product.

Moderators: OutBack, OutBack Moderator Team

Post Reply
raysun
Forum Emperor
Posts: 8601
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

Low Battery Cut-Off with FNDC

Post by raysun »

Lithium batteries are a challenge to integrate with FX class inverters due to the mismatch between Low Battery Cut-Off (LBCO) voltage required by many batteries and the LBCO voltage range settable in the Battery Protection parameters of the FX class inverters.

The FLEXnet DC battery monitor can be used in this case to track the LBCO voltage, and shut down the inverter output in the event the battery voltage is at or below LBCO.

A system with FX/FXR inverter, FLEXnet DC monitor, Mate, and Hub is required. Also a length of light gauge two conductor wire to connect the FNDC Aux relay to the Inverter / On-Off terminals on the FX.

Screenshot_20220603-172111_Word.jpg
Wire pair will connect to the Inverter On/Off terminals. The other ends will attach to the Aux terminals on the FNDC. There is no polarity to the wiring.

20220603_172626.jpg
The FNDC Aux will be programmed for LBCO by setting the (Voltage) Low parameter, (Voltage) High parameter, and Low Enable Delay.

Screenshot_20220603-175229_Firefox.jpg
Programming for a 48V nominal battery that requires a 50V Low Battery Cut-Out voltage, 52V Low Battery Cut-In voltage, and LBCO Delay of 10 minutes. Relay Mode = Auto

No other parameters are set.

NOTE: The FNDC Aux is a latching relay. In order for it to be enabled (contacts closed), the battery voltage must first be greater than or equal to (Voltage) High.
User avatar
SandyP
Forum Czar
Posts: 514
Joined: Tue Jun 21, 2011 4:44 am
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
Mate2
Outback FM60 MPPT (max output lowered to 55amps)
12 x 2V Hoppecke GEL 612 Ah C24 - 24V System (June 2011)
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset
Location: Victoria, Australia

Re: Low Battery Cut-Off with FNDC

Post by SandyP »

raysun wrote: Fri Jun 03, 2022 8:44 pm Lithium batteries are a challenge to integrate with FX class inverters due to the mismatch between Low Battery Cut-Off (LBCO) voltage required by many batteries and the LBCO voltage range settable in the Battery Protection parameters of the FX class inverters.

The FLEXnet DC battery monitor can be used in this case to track the LBCO voltage, and shut down the inverter output in the event the battery voltage is at or below LBCO.

A system with FX/FXR inverter, FLEXnet DC monitor, Mate, and Hub is required. Also a length of light gauge two conductor wire to connect the FNDC Aux relay to the Inverter / On-Off terminals on the FX.
Thanks for the write up on LBCO.

Do you feel that the Victron BMV's relay function (Low Battery Voltage and/or SoC) would also be an option for those with FX inverters but no Hub or FNDC?
-------------------------
http://spwebcam.myddns.me/
raysun
Forum Emperor
Posts: 8601
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: Low Battery Cut-Off with FNDC

Post by raysun »

Sure, the BMV series can provide LBCO Aux switching from a "stand alone" battery monitor.
User avatar
SandyP
Forum Czar
Posts: 514
Joined: Tue Jun 21, 2011 4:44 am
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
Mate2
Outback FM60 MPPT (max output lowered to 55amps)
12 x 2V Hoppecke GEL 612 Ah C24 - 24V System (June 2011)
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset
Location: Victoria, Australia

Re: Low Battery Cut-Off with FNDC

Post by SandyP »

Hmmm, looks like I will need to upgrade to the BMV-7## series as the earlier models have the relay normally open whilst the 7## series allow you to change that to normally closed.
-------------------------
http://spwebcam.myddns.me/
raysun
Forum Emperor
Posts: 8601
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: Low Battery Cut-Off with FNDC

Post by raysun »

SandyP wrote: Sun Jun 05, 2022 4:55 am Hmmm, looks like I will need to upgrade to the BMV-7## series as the earlier models have the relay normally open whilst the 7## series allow you to change that to normally closed.
The 600 series have both Low Voltage and High Voltage sensing logic, do they not? If the relay is NO, then perhaps the Relay High Voltage parameter can be set to LBCI voltage, and the Clear Relay High Voltage parameter set to the LBCO voltage.

FWIW, the FNDC relay is operating like that. It's NO, so the LBCI voltage must be reached first to energize the relay.
User avatar
SandyP
Forum Czar
Posts: 514
Joined: Tue Jun 21, 2011 4:44 am
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
Mate2
Outback FM60 MPPT (max output lowered to 55amps)
12 x 2V Hoppecke GEL 612 Ah C24 - 24V System (June 2011)
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset
Location: Victoria, Australia

Re: Low Battery Cut-Off with FNDC

Post by SandyP »

raysun wrote: Sun Jun 05, 2022 5:53 am
SandyP wrote: Sun Jun 05, 2022 4:55 am Hmmm, looks like I will need to upgrade to the BMV-7## series as the earlier models have the relay normally open whilst the 7## series allow you to change that to normally closed.
The 600 series have both Low Voltage and High Voltage sensing logic, do they not? If the relay is NO, then perhaps the Relay High Voltage parameter can be set to LBCI voltage, and the Clear Relay High Voltage parameter set to the LBCO voltage.

FWIW, the FNDC relay is operating like that. It's NO, so the LBCI voltage must be reached first to energize the relay.
Yep, it has both high and low settings and you are correct that, based on the manual, you could "trick" it by setting high as low and visa versa assuming they do not have any "hidden" logic that checks the relative values of each.

Rl: Relay low voltage. When the battery voltage falls below this value for more than
10 seconds the alarm relay will be activated.
Rlc: Clear relay low voltage. When the battery voltage rises above this value, the
relay will be de-activated. This value needs to be greater than or equal to Rl.
Rh: Relay high voltage. When the battery voltage rises above this value for more
than 10 seconds the relay will be activated.
Rhc: Clear relay high voltage. When the battery voltage falls below this value, the
relay will be de-activated. This value needs to be less than or equal to Rh.
-------------------------
http://spwebcam.myddns.me/
raysun
Forum Emperor
Posts: 8601
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: Low Battery Cut-Off with FNDC

Post by raysun »

It should be fairly easy to test on the next charge cycle.
Set Rh = Absorb Voltage - 0.2V
Set Rhc = Float Voltage + 0.2V

For testing, Ah and Ahc parameters could be set to the values above to have a really annoying audible (and visual) indication the programming is working.

Better for real life, set Al and Alc so the alarm is enabled during the LBCO event.
solartribe
Forum Expert
Posts: 52
Joined: Wed Jul 29, 2015 7:40 am
My RE system: 6 x 24v 235w poly
1 x FM80
1x GFX1312
4x 100A battleborn LFP batteries
Honda EU2000
Mate3s Optics. Hub 10.3
Note- I install many offgrid systems, so a post could be referring to a different setup- however I install exclusively Outback.

Re: Low Battery Cut-Off with FNDC

Post by solartribe »

raysun wrote: Fri Jun 03, 2022 8:44 pm Lithium batteries are a challenge to integrate with FX class inverters due to the mismatch between Low Battery Cut-Off (LBCO) voltage required by many batteries and the LBCO voltage range settable in the Battery Protection parameters of the FX class inverters.

The FLEXnet DC battery monitor can be used in this case to track the LBCO voltage, and shut down the inverter output in the event the battery voltage is at or below LBCO.

A system with FX/FXR inverter, FLEXnet DC monitor, Mate, and Hub is required. Also a length of light gauge two conductor wire to connect the FNDC Aux relay to the Inverter / On-Off terminals on the FX.

Wire pair will connect to the Inverter On/Off terminals. The other ends will attach to the Aux terminals on the FNDC. There is no polarity to the wiring.

The FNDC Aux will be programmed for LBCO by setting the (Voltage) Low parameter, (Voltage) High parameter, and Low Enable Delay.

Programming for a 48V nominal battery that requires a 50V Low Battery Cut-Out voltage, 52V Low Battery Cut-In voltage, and LBCO Delay of 10 minutes. Relay Mode = Auto

No other parameters are set.

NOTE: The FNDC Aux is a latching relay. In order for it to be enabled (contacts closed), the battery voltage must first be greater than or equal to (Voltage) High.
Curious if anyone who has installed and tested this setup has come across issues? For me, it does not work... my system: 12v Battleborn x4, Outback FXR2012, FNDC, FM80, MATE3s (FW1.4.7), HUB4.)
On my system, with the delays set to 0, L set to 13.0 and H set to 13.6 for testing, the relay will open as soon as battery voltage drops below the LVCO of 13.0V. As soon as battery voltage rises above 13.0, the relay closes. It NEVER has to reach the high voltage setpoint. I have repeated this several different ways with different voltages and different delays... it doesnt seem to matter.
What is particularly troublesome though is that occasionally if the battery voltage changes too quickly, the relay wont catch it. I.e. voltage goes below the LVCO, inverter turns off, voltage bounces back above the LVCO, and inverter turns back immediately pushing the voltage back below the LVCO. In this case the relay doesnt always open. The MATE3S will say that the relay is AUTO OFF, but its like the FNDC never received the signal from the Mate3s, or perhaps the FNDC was too busy processing the last signal that it never received the latest signal to turn off. Raising voltage above the LVCO and then slowly lowering it resets the relay and all works correctly again. Even with the delays set to 1 min, this still seems to happen... though I am not sure why. Notably though, the High voltage setting doesnt have to be met in any of these cases.
MJSullivan56
Forum Guru
Posts: 203
Joined: Fri Aug 13, 2021 4:35 pm
My RE system: BOM
(12) REC alpha-series 370W solar panels (4.4kW)
(12) Tigo TS4-A-O optimizers
(1) Tigo CCA outdoor kit
(1) Outback Radian FPR-4048A-300AFCI pre-wired inverter/charger
(3) Fortress eFlex 5.4kWh batteries (16.2kWh)
(1) Outback RSI
(3) MidNite Solar surge protectors
(1) Midnite MNPV6-250 combiner
(12) Tamarack racking kits
(2) QBox Junction Boxes
Location: Boston MA

Re: Low Battery Cut-Off with FNDC

Post by MJSullivan56 »

raysun wrote: Fri Jun 03, 2022 8:44 pm Lithium batteries are a challenge to integrate with FX class inverters due to the mismatch between Low Battery Cut-Off (LBCO) voltage required by many batteries and the LBCO voltage range settable in the Battery Protection parameters of the FX class inverters.

The FLEXnet DC battery monitor can be used in this case to track the LBCO voltage, and shut down the inverter output in the event the battery voltage is at or below LBCO.

A system with FX/FXR inverter, FLEXnet DC monitor, Mate, and Hub is required. Also a length of light gauge two conductor wire to connect the FNDC Aux relay to the Inverter / On-Off terminals on the FX.
Thanks for this. However, most systems with RSI (including mine) already make use of these pins for rapid shutdown.
Probably would still work together in tandem -- thoughts?

M
raysun
Forum Emperor
Posts: 8601
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: Low Battery Cut-Off with FNDC

Post by raysun »

Curious if anyone who has installed and tested this setup has come across issues? For me, it does not work... my system: 12v Battleborn x4, Outback FXR2012, FNDC, FM80, MATE3s (FW1.4.7), HUB4.)
On my system, with the delays set to 0, L set to 13.0 and H set to 13.6 for testing, the relay will open as soon as battery voltage drops below the LVCO of 13.0V. As soon as battery voltage rises above 13.0, the relay closes. It NEVER has to reach the high voltage setpoint. I have repeated this several different ways with different voltages and different delays... it doesnt seem to matter.
I tested it under multiple scenarios (LBCO, HBCO) and it work as described in the OP. The only obvious differences were a 48V (vs 12V) battery, and a wider "delta" between Voltage High and Voltage Low setpoints.
raysun
Forum Emperor
Posts: 8601
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: Low Battery Cut-Off with FNDC

Post by raysun »

Thanks for this. However, most systems with RSI (including mine) already make use of these pins for rapid shutdown.
Probably would still work together in tandem -- thoughts?
The FNDC Aux relay provides a set of dry contacts rated (IIRC) 36V @ 5A max. These can feed an external, properly powered, circuit that could drive any number of functions, as long as they all work from the same threshold points.
Post Reply