What Sell Voltage setting for Grid-Tie 24v Battery Bank

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What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby foo on Thu May 18, 2017 9:12 am

VFXR3524A Inverter
24V Battery Bank @ 210AH
Mate3

Do I set the sell point at the 100% Full rating for the batteries which is 25.2V
or at the Float Voltage rating of the batteries which is 27.2V?

Thanks in advance.
foo
OutBack Whiz
 
Posts: 44
Joined: Thu Jun 30, 2016 1:25 pm
My RE system: VFXR3524A Inverter
3.5kW Solar Array @48V
24V Battery Bank - 210AH (4x105AH @12V) -FLA
Mate3
Renogy Tracer 4210 40 Amp MPPT Charge Controllers x 3, 12/24V 100VDC Input
Outback Power FLEXmax FM80 MPPT Solar Charge Controller

Re: What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby Sandra Herrera on Fri May 19, 2017 3:13 pm

What type of batteries? Why is float voltage so high?
Usually SELL voltage depend on the type batteries and the application, a good rule of thumb used in the industry is float voltage.
I would recommend you check with battery manufacturer on your float voltage
Sandra Herrera
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Sandra Herrera
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Re: What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby foo on Fri May 19, 2017 5:15 pm

FLA

Thank you for making me double check that. I thought I had grabbed that off of the pdf but it seems I grabbed it off a scale I found long ago on the net.

I will promptly change the float voltage; but I do have a question:
How do I know which voltage in the range specified is right for my bank?
http://www2.exide.com/Media/files/Location%20Data/Battery%20Charging%20%26%20Storage%20Specs%20%2011_13_15.pdf

The range is 26.4V to 26.8V
What I will set for right now is 26.8V for float and 26.4V for Sell.

Thanks again for the catch.
foo
OutBack Whiz
 
Posts: 44
Joined: Thu Jun 30, 2016 1:25 pm
My RE system: VFXR3524A Inverter
3.5kW Solar Array @48V
24V Battery Bank - 210AH (4x105AH @12V) -FLA
Mate3
Renogy Tracer 4210 40 Amp MPPT Charge Controllers x 3, 12/24V 100VDC Input
Outback Power FLEXmax FM80 MPPT Solar Charge Controller

Re: What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby foo on Mon Nov 20, 2017 8:39 pm

Sandra Herrera wrote:What type of batteries? Why is float voltage so high?
Usually SELL voltage depend on the type batteries and the application, a good rule of thumb used in the industry is float voltage.
I would recommend you check with battery manufacturer on your float voltage


I'm revisiting this because I just installed a hub and I'm configuring the Mate3 for the attached Flexmax 80.

I've been using the float voltage for the Selling setting.

I still question what I should use as the float voltage setting. Should the Float Voltage setting AND the Sell Voltage setting be the same, a decimal or two apart? Will being so close cause issues?

Thanks in advance for any info.
foo
OutBack Whiz
 
Posts: 44
Joined: Thu Jun 30, 2016 1:25 pm
My RE system: VFXR3524A Inverter
3.5kW Solar Array @48V
24V Battery Bank - 210AH (4x105AH @12V) -FLA
Mate3
Renogy Tracer 4210 40 Amp MPPT Charge Controllers x 3, 12/24V 100VDC Input
Outback Power FLEXmax FM80 MPPT Solar Charge Controller

Re: What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby Mike Curran on Tue Nov 21, 2017 9:21 am

My experience has been that when you set them too close my system would go into float mode on a bright sunny day when it should be selling. I set sell voltage to my desired float setting. Float a bit higher - for me it's not important, my charge controllers are set up to drive toward absorb but are limited by the sell setting.

I believe I read a recommendation somewhere that float should be set 0.2 volts higher but be careful, sell voltage is not a temperature compensated value while float voltage is. If you're using an RTS then on a bright, sunny, cold day when battery voltage would like to go higher, your sell setting would prevent it and you'd be undercharging your batteries. Note this is only a factor to consider if your battery is in an unheated space.
Mike Curran
OutBack Guru
 
Posts: 339
Joined: Sat Aug 28, 2004 6:28 pm
Location: Chagrin Falls, Ohio
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60
- 6 (2×3) ALEO S79-300's into one FM80
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC
- 12 Surrette/Rolls 2V x 1766Ah
- Hub10.3, Mate3, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

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

Re: What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby foo on Tue Nov 21, 2017 5:02 pm

Those are good points. I do have RTS on the inverter and the CC.

I'm thinking I'll have to have one setpoint at a .2v diff for float for 9 months of the year and then during those bitter cold 3 months, have a larger margin.

Thanks for the feedback.

I am wondering why Sell voltage isn't temp compensated in any case that there is temp compensation. Wondering if anyone is running into that issue or what solution may exist.
foo
OutBack Whiz
 
Posts: 44
Joined: Thu Jun 30, 2016 1:25 pm
My RE system: VFXR3524A Inverter
3.5kW Solar Array @48V
24V Battery Bank - 210AH (4x105AH @12V) -FLA
Mate3
Renogy Tracer 4210 40 Amp MPPT Charge Controllers x 3, 12/24V 100VDC Input
Outback Power FLEXmax FM80 MPPT Solar Charge Controller

Re: What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby Mike Curran on Tue Nov 21, 2017 6:11 pm

I used to seasonally adjust my sell voltage (as you're planning), but now my battery box is heated so it's no longer an issue :wink: .

Battery heating system.jpg
Mike Curran
OutBack Guru
 
Posts: 339
Joined: Sat Aug 28, 2004 6:28 pm
Location: Chagrin Falls, Ohio
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60
- 6 (2×3) ALEO S79-300's into one FM80
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC
- 12 Surrette/Rolls 2V x 1766Ah
- Hub10.3, Mate3, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

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

Re: What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby foo on Tue Nov 21, 2017 6:17 pm

Ok, that looks amazing.

How does that work? Are you letting hot water from showers and such do the work somehow?
foo
OutBack Whiz
 
Posts: 44
Joined: Thu Jun 30, 2016 1:25 pm
My RE system: VFXR3524A Inverter
3.5kW Solar Array @48V
24V Battery Bank - 210AH (4x105AH @12V) -FLA
Mate3
Renogy Tracer 4210 40 Amp MPPT Charge Controllers x 3, 12/24V 100VDC Input
Outback Power FLEXmax FM80 MPPT Solar Charge Controller

Re: What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby Mike Curran on Tue Nov 21, 2017 6:24 pm

Glad you asked! I've got an outdoor woodburning furnace that circulates hot water to the house for heat. Last winter I tapped into it for the battery boxes. There's a thermostat set for 15C that opens a motor-operated valve and starts a 12V pump. Since we also have an indoor woodburning stove, we could spare the tapped hot water for this purpose. There are some brass fittings in there so over time I'll have to keep an eye on things, but so far works good. Garage sometimes gets below freezing but battery stays toasty.
Mike Curran
OutBack Guru
 
Posts: 339
Joined: Sat Aug 28, 2004 6:28 pm
Location: Chagrin Falls, Ohio
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60
- 6 (2×3) ALEO S79-300's into one FM80
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC
- 12 Surrette/Rolls 2V x 1766Ah
- Hub10.3, Mate3, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

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

Re: What Sell Voltage setting for Grid-Tie 24v Battery Bank

Postby foo on Wed Nov 22, 2017 1:16 pm

That is awesome. I love it. Good job.
foo
OutBack Whiz
 
Posts: 44
Joined: Thu Jun 30, 2016 1:25 pm
My RE system: VFXR3524A Inverter
3.5kW Solar Array @48V
24V Battery Bank - 210AH (4x105AH @12V) -FLA
Mate3
Renogy Tracer 4210 40 Amp MPPT Charge Controllers x 3, 12/24V 100VDC Input
Outback Power FLEXmax FM80 MPPT Solar Charge Controller


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