FNDC Charge Termination and FM80

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FNDC Charge Termination and FM80

Postby herodotus on Wed Jun 08, 2016 11:35 am

Hi All,

Over the last couple of weeks I've been putting together a solar installation for our off-grid house in the Spanish mountains (details in sig). By the end of the week I hope to be starting the commissioning processes and configuring everything. I've been doing a lot of reading to try and make sure I do things properly. One thing that puzzles me is exactly how the FNDC fits in to the charging process once the system is fully configured. AIUI, the FNDC provides the most accurate measurement of current flowing into the batteries in the system, since it can compensate for any loads being drawn by the inverter. As such it would seem to make sense to use an "end amps" threshold measured by the FNDC to end the absorb phase of charging and move into float.

Unfortunately, it is not at all clear from the Outback manuals (or indeed, anything else I've managed to find online) whether this actually works, and if it does, what the relationship is to the settings available for the FM80 itself. I can configure "Return Amps" for the FNDC (and calibrate it against SG readings/actual live current readings over a few cycles). According to the Mate3 manual, I can also enable "Charge Termination Control" for the FNDC, which will allow the FNDC to stop charging when the parameters are met. So far so good. The problem is that the description of this feature in the Mate3 manual is
allows the battery charging to be stopped for all inverters on the system, once the charging parameters of the Flexnet DC have been met
(emphasis mine) . This implies that the setting only implies to inverters. Interestingly, however, a friend who has been helping me pointed out that the Mate2 manual explicitly says that this feature terminates the charge cycle for both inverters and charge controllers. So I'm wondering if this is just some bad wording/a typo in the Mate3 manual?

Either way, I'm also not clear how this setting relates to the "Absorb End Amps" setting on the FM80 itself. Will the charge cycle stop if end amps drops below either the value in the FM80 config OR the FNDC charge parameters are met? Or does the FM80 somehow use the end amps value from the FNDC? Or does setting the FNDC charge termination disable the FM80 control somehow? It's all a bit unclear, can anyone shed any light on this for me?

Many thanks!
15 x Munchen 250W MSP250AS-30.EU, FM80, FlexNet DC, VFX3048E, HUB10, MATE3, 2x FWSHUNT-500, 8 x Rolls S605
herodotus
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My RE system: 15 x Munchen 250W MSP250AS-30.EU, FM80, FlexNet DC, VFX3048E, HUB10, MATE3, 2x FWSHUNT-500

Re: FNDC Charge Termination and FM80

Postby blackswan555 on Thu Jun 09, 2016 3:24 am

End amps is not normally used, Too unreliable due to temp and load fluctuation for most applications, The FNDC takes a LOT of setting up and as you have new batteries they will take time to "run in" ( around 70 x 50% DOD cycles) so it is not recommended to use it to until you "know" your batteries well, it will then drift over time, So recalibrate it to SG's often to start, Do not let it take control untill you are satisfied "it" corresponds to SG'S, ( SG's are right, FNDC is an educated guess, only as good as it was set up,,,, :smile: )
Initial setup is best done with timed absorb cross referenced to SG's,

bat commissioning, I guess you have read below ? pay special attention to the commissioning section
INITIAL CHARGE
A battery may not be fully charged when received. An initial charge brings the battery to
an operational state. Before charging, electrolyte level in each cell should be checked.
Please ensure the electrolyte (liquid) covers the plates completely. It is normal for
electrolyte levels to lower as the battery case will bulge slightly after filling. If the plates
are exposed, add distilled water until all are just submerged. It is important not to overfill
each cell as the electrolyte level will rise during the charging process. Charge voltages
are indicated in Table 2.
The specific gravity of electolyte in a battery is the most accurate measurement to
determine if the cells are in fact, fully charged. The specific gravity should be constant
for 3 hours for an accurate full charge reading. Check the state of charge as related to
specific gravity. Initial charging may take 10 hours. Once the battery is fully charged,
verify the electrolyte level in the cell once more. The fluid should be 1/4” – 1/2”
below the vent tube on each cell as shown in Figure 8. Carefully add distilled water
to adjust the level if needed.
The jist of it being, They must be fully charged on first "run" It is also a good time to do EQ :smile: It is also critical that the batteries to be full when you first connect FNDC, it defaults to 100%

Have a good one
Tim

rolls manual http://rollsbattery.com/uploads/pdfs/do ... Manual.pdf
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
blackswan555
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My RE system: Other peoples, VFX "E" versions, FLA`s, Generators.

Re: FNDC Charge Termination and FM80

Postby herodotus on Thu Jun 09, 2016 3:33 am

blackswan555 wrote:End amps is not normally used, Too unreliable due to temp and load fluctuation for most applications, The FNDC takes a LOT of setting up and as you have new batteries they will take time to "run in" ( around 70 x 50% DOD cycles) so it is not recommended to use it to until you "know" your batteries well, it will then drift over time, So recalibrate it to SG's often to start, Do not let it take control untill you are satisfied "it" corresponds to SG'S, ( SG's are right, FNDC is an educated guess, only as good as it was set up,,,, :smile: )
Initial setup is best done with timed absorb cross referenced to SG's,


Hi,
Yeah, I've read enough stuff on here to realise that I need to be careful about getting things calibrated before I let the FNDC take control. I'm intending to charge the batteries manually initially and cross-reference to SG readings in order to calibrate everything, then equalise and recheck as you suggest.

When you say "End amps is not normally used" I assume you are referring to the setting on the FM80 itself, rather than the return amps + charge termination on the FNDC? Do I take it from this that I should set the FM80 End amps setting to zero so that it has no effect? I'd really like to know what the formal relationship is between all these related settings so that I can be sure I configure things right (after it's all calibrated, of course).

Cheers,
15 x Munchen 250W MSP250AS-30.EU, FM80, FlexNet DC, VFX3048E, HUB10, MATE3, 2x FWSHUNT-500, 8 x Rolls S605
herodotus
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Posts: 17
Joined: Wed Jun 08, 2016 12:23 am
My RE system: 15 x Munchen 250W MSP250AS-30.EU, FM80, FlexNet DC, VFX3048E, HUB10, MATE3, 2x FWSHUNT-500

Re: FNDC Charge Termination and FM80

Postby blackswan555 on Thu Jun 09, 2016 4:12 am

When you say "End amps is not normally used" I assume you are referring to the setting on the FM80 itself, rather than the return amps + charge termination on the FNDC? Do I take it from this that I should set the FM80 End amps setting to zero so that it has no effect?
Both, set them to "0" Problem with end amps is that it does not take into consideration temp or load, so EG if you set it to 10 amps & it is "right" that day, tomorrow if the Mrs has the TV on it will not drop below due to TV load, & the opposite on other days, the other thing is temp, That will also change end amps,, Not consistent,


I need to be careful about getting things calibrated before I let the FNDC take control
:grin: Very,,,,, it may be a while,,, if at all #-o Get it running "nice" on timed absorb, you will be somewhere around 3 1/2 TO 4 hrs on solar, a little long is not a problem as long as water usage is not too high & can be monitored regularly, It will reduce need for EQ, (no I do not like them :smile: )

Tim

ps Can not see them but I presume you have temp sensing on all charge sources ? ( sorry, my pet "bug")
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
blackswan555
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Posts: 2567
Joined: Sat Aug 30, 2008 5:50 am
Location: Ibiza Spain,
My RE system: Other peoples, VFX "E" versions, FLA`s, Generators.

Re: FNDC Charge Termination and FM80

Postby herodotus on Thu Jun 09, 2016 9:52 am

blackswan555 wrote: Both, set them to "0" Problem with end amps is that it does not take into consideration temp or load, so EG if you set it to 10 amps & it is "right" that day, tomorrow if the Mrs has the TV on it will not drop below due to TV load, & the opposite on other days, the other thing is temp, That will also change end amps,, Not consistent,


Ok, now I'm really confused. I thought one of the major reasons for using an FNDC with two shunts in the first place was precisely that it can discount the load coming out via the inverter shunt when looking at what is going into the batteries from the CC. The temperature thing I understand, but our batteries are in a reasonably well insulated room to start with, so temperature variation should not be *too* dramatic. There are others I've spoken to who swear by Return Amps as the right way to configure absorption ending, so I'm guessing this is an area where there are competing schools of thought...

blackswan555 wrote:ps Can not see them but I presume you have temp sensing on all charge sources ? ( sorry, my pet "bug")


I have an RTS plugged into the inverter. AIUI, since the inverter and everything else is networked together via the Hub10, that's all I need, because they share the information from the single RTS.
15 x Munchen 250W MSP250AS-30.EU, FM80, FlexNet DC, VFX3048E, HUB10, MATE3, 2x FWSHUNT-500, 8 x Rolls S605
herodotus
Forum Member
 
Posts: 17
Joined: Wed Jun 08, 2016 12:23 am
My RE system: 15 x Munchen 250W MSP250AS-30.EU, FM80, FlexNet DC, VFX3048E, HUB10, MATE3, 2x FWSHUNT-500

Re: FNDC Charge Termination and FM80

Postby blackswan555 on Thu Jun 09, 2016 1:33 pm

Ok, now I'm really confused. I thought one of the major reasons for using an FNDC with two shunts in the first place was precisely that it can discount the load coming out via the inverter shunt when looking at what is going into the batteries from the CC.

Have a look at https://en.wikipedia.org/wiki/Peukert%27s_law vs capacity tables, it is near on impossible to calculate amps in & out accurately, I do not mind admitting I do not like FNDC as is does tend to give a false sense of security,It is as good as it is set up and will drift over time, But there is nothing better on the market, use it as a battery monitor & calibrate often against SG's, It is a good tool, ( do not forget, any battery monitor does not know you or your loads etc and they will change, it is a monitor, "it" does not know the internal condition / charge,) SG SG and more SG ! :smile:

Tim
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
blackswan555
Forum Emperor
 
Posts: 2567
Joined: Sat Aug 30, 2008 5:50 am
Location: Ibiza Spain,
My RE system: Other peoples, VFX "E" versions, FLA`s, Generators.


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