WIDE or LIMIT? RTS Compensation

Discussion about the FM100, FM80, and FM60 Charge Controllers

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JeffinthePeace
Forum Guru
Posts: 102
Joined: Mon Oct 01, 2018 8:20 pm
My RE system: VFX3524 Inverter/Charger.
2 x FM80 Charge Controllers.
12 Trina PV panels: 365W, 48.0Voc, 9.3A Imp.
Total 4380W PV.
Midnight Sun Combiner Boxes.
Mate (Original) and Hub4.
TriMetric 2020 Battery Monitor.
1065 Ah Yuasa 85T-21 FLA 24V battery bank (10 yrs old).
10kW 120/240VAC Kubota/Stamford diesel generator.
PSX-240 Auto Transformer for generator charging.
No Utility Grid available.
Location: Peace Country, British Columbia

WIDE or LIMIT? RTS Compensation

Post by JeffinthePeace » Sun Mar 17, 2019 2:08 pm

Hello All -
I have been wondering why my batteries have been Absorbing at such a low voltage (28.2V) and NOT at the Absorb setpoint (29.6V).
In the Advanced menu, I see the RTS Compensation setting, either Wide or Limit.
By default my Charge ControllerÔÇÖs were set to Limit, which (apparently) limited the Absorbing voltage to 28.2V by default?!
But, I am using an RTS (plugged into the Inverter, which is plugged into Port 1 of the Hub) so should I be using the Wide setting??
Or should I use the Limit function, in which case:
Upper = 29.6V (that is, equal to my Absorb setpoint)
Lower = 27.0V (that is, equal to my Float setpoint)

In general, I think I could use some advice with the setpoints on the charge controllers, versus the setpoints on the mate/inverter.

Mike Curran
Forum Emperor
Posts: 1788
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: WIDE or LIMIT? RTS Compensation

Post by Mike Curran » Sun Mar 17, 2019 5:30 pm

The FM80 manual offers an explanation of when to use the limit settings:
- During cold weather, a battery often requires a higher charging voltage. Some inverters might not accommodate these higher voltages and can shut down during charging, cutting off power to their loads.
- During hot weather, limiting the RTS Compensation values assures the voltage stays high enough to charge the batteries instead of dropping too low in reaction to a higher ambient temperature.
- Battery manufacturer specifications indicate not to exceed a certain voltage or battery damage could occur. In all cases, the batteries should be monitored to ensure they are being charged according to the battery manufacturerÔÇÖs recommendations. RTS Compensation has two options available. -
WIDE allows the RTS full control over charging. This option uses the default values for the RTS.
- LIMIT sets the minimum and maximum voltages for the RTS.
In general, I think I could use some advice with the setpoints on the charge controllers, versus the setpoints on the mate/inverter.
I can't remember where I read it but I seem to recall a recommendation that the voltage settings (float, absorb, equalize) on the charge controller should be set higher than those on the inverter/charger. IIRC, for a 24 volt system, all settings should be 0.2 volts higher, and on a 48 volt system, 0.4 volts higher. The reasoning was to keep the charge controllers working (using PV) if/when the inverter/charger is also trying to reach the charging targets. Otherwise the FM80'S might slack off when the sun's out and you're using the grid or a genny to charge. Not sure this answers your question but hope it's helpful.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

JeffinthePeace
Forum Guru
Posts: 102
Joined: Mon Oct 01, 2018 8:20 pm
My RE system: VFX3524 Inverter/Charger.
2 x FM80 Charge Controllers.
12 Trina PV panels: 365W, 48.0Voc, 9.3A Imp.
Total 4380W PV.
Midnight Sun Combiner Boxes.
Mate (Original) and Hub4.
TriMetric 2020 Battery Monitor.
1065 Ah Yuasa 85T-21 FLA 24V battery bank (10 yrs old).
10kW 120/240VAC Kubota/Stamford diesel generator.
PSX-240 Auto Transformer for generator charging.
No Utility Grid available.
Location: Peace Country, British Columbia

Re: WIDE or LIMIT? RTS Compensation

Post by JeffinthePeace » Sun Mar 17, 2019 6:02 pm

Hm OK
What is your recommended setpoint for:
Absorbing: I am at 29.6V
Float: 27.0V
ReBulk Voltage? I am at 24.0V
*RTS Compensation? I have mine set to Wide: A 29.5V & F 26.8V
Absorb Time: 4hrs
Absorb Rnd Amps: 40A (2% of Ah capacity of battery)
*It is mostly the RTS Compensation settings I am concerned about. It just seems there is a lot of juice pumping into the battery - which is awesome - but maybe too much.
And the system will go from Bulk, To Absorb, but then back to Bulk again later in the day?

Mike Curran
Forum Emperor
Posts: 1788
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: WIDE or LIMIT? RTS Compensation

Post by Mike Curran » Sun Mar 17, 2019 6:18 pm

My FM80 settings are pretty close to yours:
Screenshot_20190317-211153.jpg
RTS Compensation? I have mine set to Wide: A 29.5V & F 26.8V
My limited understanding is that these settings only apply when RTS is set for limit. "Wide" allows full voltage range for temperature comp.
And the system will go from Bulk, To Absorb, but then back to Bulk again later in the day?
Strange to be sure. It would help to see what your battery voltage graph looks like while this is happening.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

petertearai
Forum Guru
Posts: 397
Joined: Fri Aug 06, 2010 4:35 pm
My RE system: 2220 watt pv, fm80, outback fxr 2000 watt inverter. Shoto 12 times 2 volt exc400 lead carbon batterys 24 volt system victron battery moniter. optics RE
Location: NewZealand North Island

Re: WIDE or LIMIT? RTS Compensation

Post by petertearai » Sun Mar 17, 2019 11:05 pm

the limit is especially usefull on sealed agm type battery's that can be damaged by high voltage . I have my upper limit set .2 volts below the maximum recommend by battery manufacturer .
On my older battery's , that were flooded, i set it to wide . Flooded aren't so particular if they get an over voltage
2220 pv. fm80. 12 times 2 volt exc shoto lead carbon 450 AH 24 volts. victron battery monitor. outback fxr 2000 watt inverter

JeffinthePeace
Forum Guru
Posts: 102
Joined: Mon Oct 01, 2018 8:20 pm
My RE system: VFX3524 Inverter/Charger.
2 x FM80 Charge Controllers.
12 Trina PV panels: 365W, 48.0Voc, 9.3A Imp.
Total 4380W PV.
Midnight Sun Combiner Boxes.
Mate (Original) and Hub4.
TriMetric 2020 Battery Monitor.
1065 Ah Yuasa 85T-21 FLA 24V battery bank (10 yrs old).
10kW 120/240VAC Kubota/Stamford diesel generator.
PSX-240 Auto Transformer for generator charging.
No Utility Grid available.
Location: Peace Country, British Columbia

Re: WIDE or LIMIT? RTS Compensation

Post by JeffinthePeace » Mon Mar 18, 2019 8:09 am

OK...it sounds like I should be using the WIDE settings, and the parameters are automatically set according to the Absorb and Float settings in the CHARGER MENU settings.
Thanks Gents, much appreciated!
J

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