2 FM80s showing different battery voltage

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2 FM80s showing different battery voltage

Postby Boonys on Tue Dec 04, 2018 9:58 am

I have two FM80s float controlled thru a Mate3. If I go into the charge controller logs in the Mate3 and toggle between the two ports the FM80s are in, I get two different "min. bat." voltages.

How is that possible. All the wiring between the charge controllers and batteries is identical. If I hit the minus and go back in days, one one day one FM80 is higher, go back another day and the other charge controller is higher. There is no pattern to it. It's completely random. Yesterday it showed the minimum battery voltage of port 1 FM80 was 50.6 volts and the port 3 FM80 was 50.1 volts. That may not seem like much difference, but I'm trying to solve an issue that may be caused by this difference. I can go back several days and they all read different voltages as compared between the two charge controllers. The FNDC is in port 2, as the installation manual states in much be in port 2 or higher.

Thanks.
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Re: 2 FM80s showing different battery voltage

Postby Mike Curran on Tue Dec 04, 2018 11:27 am

Maybe a dumb question, but since you didn't mention it, I must ask: Have you calibrated them?
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
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Re: 2 FM80s showing different battery voltage

Postby Boonys on Tue Dec 04, 2018 2:09 pm

Yes, they're calibrated.

I'm on batteries only at night so I won't be back here till tomorrow.

Any suggestion or questions are appreciated!
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Re: 2 FM80s showing different battery voltage

Postby blackswan555 on Wed Dec 05, 2018 3:56 am

Yes, they're calibrated
When did you calibrate them ? what stage of charging ? EG, if you calibrate when at full charging capacity, That will be right, If you calibrate near your low voltage, that will be right, But always seems a little discrepancy one situation to the other,

Tim
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Re: 2 FM80s showing different battery voltage

Postby Boonys on Wed Dec 05, 2018 12:11 pm

They are well calibrated. I have compared the voltages many times.

Here's what I'm getting in the mate3 charge controller log going back 6 days:

Port 1 Port 3

min. max. min. max.

50.0 60.9 50.0 60.9
50.1 60.6 50.6 60.6
50.2 60.5 50.1 60.5
50.3 60.2 50.1 50.7*
50.3 60.2 50.1 60.5
50.4 50.8* 50.3 60.1

Notice on the 4th and 6th day back where I've placed an asterisk.

This is the problem that I'm trying to solve.
On the 4th and 6th day back, after my system absorbed completely, later in the day the one of the charge controllers resets to 0 absorb and starts the absorb cycle all over again. I've got the Mate3 set properly to coordinate the two controllers and it stops absorbing both when one reaches full absorb. Then later, one will start all over again.


Thanks! Any info is appreciated.
Last edited by Boonys on Thu Dec 06, 2018 1:53 pm, edited 1 time in total.
Boonys
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Re: 2 FM80s showing different battery voltage

Postby Boonys on Thu Dec 06, 2018 1:52 pm

It seems to me the only way these numbers could occur, is they are being recorded at different times.

The voltages are never further apart than about half a tenth. The only time you see that is when the voltage in raising or lowering. Then occationally one will go up a tenth of a volt, the other one will raise a tiny bit later...less then a second. That's the only time the voltages are different.
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Re: 2 FM80s showing different battery voltage

Postby Kurt Lundquist on Fri Dec 07, 2018 8:51 am

Boonys wrote:The FNDC is in port 2, as the installation manual states in much be in port 2 or higher


If you have VFX3648 inverters they should be in ports 1 and 2 of the Hub. If you have VFXR the second inverter would be in port 7 if you have a 120/240V system. I know this doesn't address your question but I thought I should mention it.

Personally, I wouldn't bat an eye on seeing .4 of a volt difference on the battery MIN between two controllers.

Do all the controllers have the same firmware version?

-Kurt
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Re: 2 FM80s showing different battery voltage

Postby Boonys on Fri Dec 07, 2018 11:05 am

.
.Yes, same firmware.

Yes, last year I configured my system as such:

port 1, VFXR3648
port 2, FNDC
port 3, FM80 #1
port 4, FM80 #2

I had the same problem, that one of the FM80s would reset the absorb back to 0 and start absorbing all over again. Toward the end of the day...4-5pm.

I found a bigger problem tho, going into winter.

I sometimes go from 4pm till 8:30am the next morning, without generating any power from the solar panels, and when it dropped below freezing, I had to get up in the middle of the night and turn off the inverter to keep the battery voltage from dropping too low and freezing. I just don't use it much in the winter as a result. It's off and not even connected to the Mate3.

At the moment, I'm using an inverter that draw 10 watts, no load power and my batteries bottom out at 50 volts on the coldest, longest nights.

I know the RTS must be plugged into whatever equipment is in port 1 and the FNDC in port 2, so that why I've got it as:
port 1, FM80 #1
port 2, FNDC
port 3, FM80 #2.

It is typical that the #2 FM80 has been the one that restarts absorb, even tho the rebulk is at 48 and the system is floating 54 to 55.2 volts (depending on the temp) when it restart the absorb cycle.

I have tried a few configurations with the same results.

I appreciate your input.
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My RE system: 2)FM80s-1)FM60, 2)3648 Inverters.....

Re: 2 FM80s showing different battery voltage

Postby Mike Curran on Sat Dec 08, 2018 4:44 pm

Boonys wrote:I sometimes go from 4pm till 8:30am the next morning, without generating any power from the solar panels, and when it dropped below freezing, I had to get up in the middle of the night and turn off the inverter to keep the battery voltage from dropping too low and freezing. I just don't use it much in the winter as a result. It's off and not even connected to the Mate3

This is kind of peripheral to your main question, but why aren't you setting the Low Battery Cutout (LBCO) so your system shuts off the inverter for you? One less thing you have to do...
Screenshot_20181208-183604.jpg
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
Mike Curran
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Posts: 861
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: 2 FM80s showing different battery voltage

Postby Boonys on Sun Dec 09, 2018 8:16 am

Mike Curran wrote:This is kind of peripheral to your main question, but why aren't you setting the Low Battery Cutout (LBCO) so your system shuts off the inverter for you? One less thing you have to do...


I looked at that. I wanted it to shut down at 49.9 volts, but the setting doesn't go that high. With the other inverter, I generally don't see lower than 50.0....that keeps the batteries above 80%. The batteries last longer.
Boonys
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My RE system: 2)FM80s-1)FM60, 2)3648 Inverters.....


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