Batteries charging at lower voltage than set voltage

Discussion about the OutBack Energy Cell Batteries
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mevenable
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Joined: Mon Mar 12, 2018 1:04 pm
My RE system: GS 8048 inverter, FM80 charge controller, 2 strings of 4 NC200 batteries, soon to be 3, 15 panels 270W each (4 kW), Mate3s

Batteries charging at lower voltage than set voltage

Post by mevenable » Sun Mar 18, 2018 4:22 pm

I have 2 strings of four NC106 batteries (48 V) and have a temperature sensor cable. I have Absorption set for 57.6 V and flotation for 54.4 V. The Mate3 shows the un-compensated voltage, which matches what I measure with a voltmeter very well. Then if you dig back into the inverter menus you can find the temperature compensated voltage, which matches what is specified in the manual quite well for the temperature my batteries are at in any given moment. The thing is, for the typical range of battery temperature here of 31-33 C, which should require compensating by about 1 V or less, my batteries are absorbing at 56 V and floating at 52.8 V, and the temperature compensated values are 56.8 and 53.6 V respectively, according to Mate 3. Why is it not absorbing and floating at the set voltages? 3 months ago when the batteries were first installed, they did in fact do so, and they have been gradually going down. Please advise if there is something I need to set differently. I see some calibration settings, but they are more cosmetic than actual, they seem to be for example to make the uncompensated voltage on the Mate3 match the measured voltage on the batteries

Mike Curran
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My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one MX60 (2007)
- 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 (2x7) Talesun 275W
- 2 SimpliPhi 3.8 batteries, 48V, 150Ah total
- future AC coupled input from both rows of Westinghouse AC modules*
- future AC coupled input from 14 Talesun 275W, Enphase M215 modules*
* waiting for firmware update from OB

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

Re: Batteries charging at lower voltage than set voltage

Post by Mike Curran » Mon Mar 19, 2018 8:35 am

mevenable wrote:I have 2 strings of four NC106 batteries (48 V) and have a temperature sensor cable. I have Absorption set for 57.6 V and flotation for 54.4 V..... The thing is, for the typical range of battery temperature here of 31-33 C, which should require compensating by about 1 V or less, my batteries are absorbing at 56 V and floating at 52.8 V, and the temperature compensated values are 56.8 and 53.6 V respectively, according to Mate 3.
Your setpoint voltages for absorb and float are based on a battery temperature of 25°C. Since your batteries are at about 32°C, the temperature-compensated voltages for these would be adjusted by (32-25)×0.005mV/cell×24cells = 0.84 volts.

So subtract 0.84 from the setpoints. For absorb, you get 57.6 - 0.84 = 56.76, which is pretty close to your observed TC value of 56.8.

And for float, you get 54.4 - 0.84 = 53.56, pretty close to your TC value of 53.6. Unless I'm missing something, I think your system is working as it should. - Mike
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

mevenable
Forum Member
Posts: 20
Joined: Mon Mar 12, 2018 1:04 pm
My RE system: GS 8048 inverter, FM80 charge controller, 2 strings of 4 NC200 batteries, soon to be 3, 15 panels 270W each (4 kW), Mate3s

Re: Batteries charging at lower voltage than set voltage

Post by mevenable » Mon Mar 19, 2018 8:50 am

thanks mike, that matches my calculations, but that is the problem - the temperature corrected value is 56.8 and the "raw" value is 56 V - it should be a corrected value of 57.6V and a "raw" (and measured) value of 56.8 V, no?

Mike Curran
Forum Emperor
Posts: 1217
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one MX60 (2007)
- 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 (2x7) Talesun 275W
- 2 SimpliPhi 3.8 batteries, 48V, 150Ah total
- future AC coupled input from both rows of Westinghouse AC modules*
- future AC coupled input from 14 Talesun 275W, Enphase M215 modules*
* waiting for firmware update from OB

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

Re: Batteries charging at lower voltage than set voltage

Post by Mike Curran » Mon Mar 19, 2018 9:27 am

mevenable wrote:thanks mike, that matches my calculations, but that is the problem - the temperature corrected value is 56.8 and the "raw" value is 56 V - it should be a corrected value of 57.6V and a "raw" (and measured) value of 56.8 V, no?
Good question... maybe I'm looking at it "backwards", in which case I don't have an answer :???:
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

gtarolli
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Posts: 290
Joined: Thu Dec 21, 2017 11:39 am
My RE system: Outback: off-grid
- 1 GS8048A, Mate3, FlexNetDC, Hub10.3
- 2 FLEXmax 80
- 24 (8x3) 300w panels (7200w total)
- 6 SimpliPhi 3.4 kWh LI batteries (400ah , 20kWh)
- 1 Honda 3000 generator + one spare
Location: Wainiha, Kauai, HI

Re: Batteries charging at lower voltage than set voltage

Post by gtarolli » Mon Mar 19, 2018 10:46 am

I always recommend looking at the target voltage on the FM80 to double check things - that is in the Misc menu, 2 screen in (next, next). This displays the target voltage the FM80 is aiming for, it is temp. corrected. If you are in Bulk or Absorb mode, it should be the temp adjusted absorb voltage. Given your data, it seems like .8v below your set point is about right, i.e 56.8. Why you seeing observing 56.0 I don't know. Each device has a voltage reading - what are the voltages displayed on each of the FM80, inverter, FNDC? The FM80 should match its current target unless you are drawing a large load. If the FM80 target is 56 , then you have to figure out where that is coming from, e.g. if you (accidentally) have limited temp. compensation mode enabled (instead of wide), it will clamp your voltages to that range. So you can check this in the FM80 advanced menu or in opticsre

Are you on the grid? I am wondering if your inverter is perhaps charging the batteries and might be set different than the FM80? I noticed some strangeness in my system (off-grid), going in/out of Absorb/Bulk mode, so I set the inverter's charger set points to match my two FM80s, even though it never charges. I was worried that charge controller coordination might have been trying to keep all 3 charges in sync or something.

p.s. note the inverter's temp. corrected voltage should be .8v ABOVE the actual voltage.

mevenable
Forum Member
Posts: 20
Joined: Mon Mar 12, 2018 1:04 pm
My RE system: GS 8048 inverter, FM80 charge controller, 2 strings of 4 NC200 batteries, soon to be 3, 15 panels 270W each (4 kW), Mate3s

Re: Batteries charging at lower voltage than set voltage

Post by mevenable » Mon Mar 19, 2018 11:01 am

I did set the inverter at the same settings as the FM80, although I am not using it for battery charging, is in HBX, and disabled,
I did check - is set at wide for T-comp
I am not sure it totally matters? If charging at lower V, would it just take longer?

gtarolli
Forum Guru
Posts: 290
Joined: Thu Dec 21, 2017 11:39 am
My RE system: Outback: off-grid
- 1 GS8048A, Mate3, FlexNetDC, Hub10.3
- 2 FLEXmax 80
- 24 (8x3) 300w panels (7200w total)
- 6 SimpliPhi 3.4 kWh LI batteries (400ah , 20kWh)
- 1 Honda 3000 generator + one spare
Location: Wainiha, Kauai, HI

Re: Batteries charging at lower voltage than set voltage

Post by gtarolli » Mon Mar 19, 2018 11:15 am

Not sure about charging at a lower voltage ....
can you check the Target Voltage on your FM80? (page 45 in the FM80 manual)? if it is 56 then that explains it, but then you need to figure out why it is 56.

mevenable
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Posts: 20
Joined: Mon Mar 12, 2018 1:04 pm
My RE system: GS 8048 inverter, FM80 charge controller, 2 strings of 4 NC200 batteries, soon to be 3, 15 panels 270W each (4 kW), Mate3s

Re: Batteries charging at lower voltage than set voltage

Post by mevenable » Mon Mar 19, 2018 11:28 am

wow, for sure, the misc menu does list right now 53.6 as a target voltage, it is floating at a "raw" voltage of 52.8, which is just right with the temperature compensation. But, there is no way I can see there to change that target voltage. Like you say, we have to figure out why . . . unless, of course, the target voltage of 53.6 is temperature compensated, in which case we are still just low.

gtarolli
Forum Guru
Posts: 290
Joined: Thu Dec 21, 2017 11:39 am
My RE system: Outback: off-grid
- 1 GS8048A, Mate3, FlexNetDC, Hub10.3
- 2 FLEXmax 80
- 24 (8x3) 300w panels (7200w total)
- 6 SimpliPhi 3.4 kWh LI batteries (400ah , 20kWh)
- 1 Honda 3000 generator + one spare
Location: Wainiha, Kauai, HI

Re: Batteries charging at lower voltage than set voltage

Post by gtarolli » Mon Mar 19, 2018 12:10 pm

The target voltage is not settable - it is what the FM80 is using and it is temp. compensated. So 53.6 = 54.4v -.8v and the FM80 target voltage is correct for what you want. That should be the actual voltage, but it looks almost like there is double compensation or something going on? Are you sure the inverter actual voltage is not 53.6 which should match the FM80 output voltage? I would expect 53.6v for the actual inverter voltage and the temp. compensated (target) voltage as reported by the inverter is 53.6 + .8v or 54.5.

Are your charge amps limits high enough? perhaps those are too low and the charger can't feed enough amps to maintain the voltage under the loads? in which case you should see the voltage slowly drop though, which doesn't sound like your observation.

p.s. I assume your have no large load, and your PV array is large enough and it is sunny enough to maintain the float voltage? you can always test this by forcing bulk mode for a few minutes and then force float mode (on the FM80 menus).

mevenable
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Posts: 20
Joined: Mon Mar 12, 2018 1:04 pm
My RE system: GS 8048 inverter, FM80 charge controller, 2 strings of 4 NC200 batteries, soon to be 3, 15 panels 270W each (4 kW), Mate3s

Re: Batteries charging at lower voltage than set voltage

Post by mevenable » Mon Mar 19, 2018 12:13 pm

yes, there is plenty of pv to go around, and charge amp limits are set high and all that

sigh.

gtarolli
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Posts: 290
Joined: Thu Dec 21, 2017 11:39 am
My RE system: Outback: off-grid
- 1 GS8048A, Mate3, FlexNetDC, Hub10.3
- 2 FLEXmax 80
- 24 (8x3) 300w panels (7200w total)
- 6 SimpliPhi 3.4 kWh LI batteries (400ah , 20kWh)
- 1 Honda 3000 generator + one spare
Location: Wainiha, Kauai, HI

Re: Batteries charging at lower voltage than set voltage

Post by gtarolli » Mon Mar 19, 2018 1:15 pm

Stumped here as well ... you mention this lower voltage has gradually decreased over time, from the correct temp. comp. voltage down another .8v? If that is the case, then it doesn't seem like it is a setting - as that would not gradually decrease. The only thing I can think of is that the batteries are absorbing all the current. Do they go through the full absorb cycle at the expected temp. comp. voltage? i.e. before going into float mode? When was the last time they were equalized?

mevenable
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Posts: 20
Joined: Mon Mar 12, 2018 1:04 pm
My RE system: GS 8048 inverter, FM80 charge controller, 2 strings of 4 NC200 batteries, soon to be 3, 15 panels 270W each (4 kW), Mate3s

Re: Batteries charging at lower voltage than set voltage

Post by mevenable » Wed Mar 21, 2018 11:42 am

supposedly these batteries should never be equalized. There is a "refresh charge". They go through absorption at the (too low) temperature compensated voltage of 56.8 these days, and get to the point where they are only needing 3 amps (1.5% of the total amp hours of the bank) and then go to flotation

mevenable
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Posts: 20
Joined: Mon Mar 12, 2018 1:04 pm
My RE system: GS 8048 inverter, FM80 charge controller, 2 strings of 4 NC200 batteries, soon to be 3, 15 panels 270W each (4 kW), Mate3s

Re: Batteries charging at lower voltage than set voltage

Post by mevenable » Sat Mar 24, 2018 8:36 am

ok, I am onto something I think! The misc menu on the charge controller gives a target voltage that is simply a temperature compensated version of the set voltage - for example, in the morning when it is not too hot it says it is aiming to absorb at 57.2, or 0.4 C below the 57.6 setting, due to the temperature correction. As the day heats up, it changes to 57.2, or a temperature correction of 0.8 C, all as it should be. Meanwhile, the Inverter shows a temperature corrected voltage that is equal to the already temperature corrected target voltage, and an uncorrected voltage that is even lower still. In short, somehow the system is double dipping, the inverter and the charge controller are both correcting for temperature. I have to figure out how this is happening and correct it, have not yet worked it out. Any thoughts, guys?

gtarolli
Forum Guru
Posts: 290
Joined: Thu Dec 21, 2017 11:39 am
My RE system: Outback: off-grid
- 1 GS8048A, Mate3, FlexNetDC, Hub10.3
- 2 FLEXmax 80
- 24 (8x3) 300w panels (7200w total)
- 6 SimpliPhi 3.4 kWh LI batteries (400ah , 20kWh)
- 1 Honda 3000 generator + one spare
Location: Wainiha, Kauai, HI

Re: Batteries charging at lower voltage than set voltage

Post by gtarolli » Sat Mar 24, 2018 11:35 am

The uncorrected or actual voltage from the inverter is the battery voltage, not the set point. The temp corrected target voltage is not really the target voltage, it is merely the temp corrected voltage (and remember this is in the opposite direction of adjusting set points or target voltages, it is VERY confusing I agree). So it should be higher by the same delta as the FM80 adjustment but in the opposite direction.

If the inverter charging is disabled, then its settings should not matter, neither the target settings for absorb and float, or the temp adjusted battery voltage. The actual voltage on the inverter (not the temp compensated voltage) should equal the battery voltage readings on the FM80s or within .1 or .2v. If not then you need to calibrate your voltages. Once you are in absorb or float mode and you have enough PV power to sustain that voltage, the inverter actual voltage should equal the FM80 battery voltage which should equal the FM80 target voltage on the Misc menu.

Perhaps you should list the following voltages when you are in absorb mode and have enough PV power, i.e. the FM80 is throttling back its output

FM80 battery voltage
FM80 target voltage (from the Misc menu)
FNDC battery voltage
Mate3 battery voltage
Inverter actual voltage
inverter temp compensated (target) voltage

It is true the inverter and CC both compensate for temp, but in opposite directions because one is adjusting the target set point and the other is adjusting the battery voltage and leaving the set point alone. But that is fine as they do their comparisons independently.

mevenable
Forum Member
Posts: 20
Joined: Mon Mar 12, 2018 1:04 pm
My RE system: GS 8048 inverter, FM80 charge controller, 2 strings of 4 NC200 batteries, soon to be 3, 15 panels 270W each (4 kW), Mate3s

Re: Batteries charging at lower voltage than set voltage

Post by mevenable » Sat Mar 24, 2018 5:29 pm

oooo - kay. I will chew on all that. I did notice that the actual voltage on the charge controller this morning did not match the actual voltage on the batteries. I made the largest calibration I could for the CC, -0.5 V, and this seemed to make things better today, the measured voltage on the batteries plus a temperature correction that matched the battery temperature did in fact, for the first time in a long while, seem to be very close to the settings (57.6 for abs, 54.4 for float) I am getting less and less sure what anything means so I am reading the voltage on the batteries with a volt meter and adding on my own temperature correction based on 0.12 V per degree C (0.03x4 batteries). My goal is to have that match what it is supposed to be. I will look at all the voltages in all the categories as you recommend tomorrow, since I would like to understand it all better. I do not have a flexnet - I desperately wanted it, but the local company tried to install one twice, and each time managed to burn out the hub somehow (it stopped working) so we gave up. Anyhow, thanks very much for all that help.

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