Outback FM80 End Amps vs FlexNet Return Amps

herodotus · June 2016

Hi All,

I'm just in the process of building/installing my new solar system and before I start commissioning everything I want to make sure I've understand sensible starting values for it. One thing in particular that has me puzzled is the methods of ending the absorb phase of the charge. I've forked out for the whole 9 yards - Mate3, FlexNet DC, Hub and two shunts - so I'm hoping that I can set the thing up to behave relatively intelligently. Ideally, I'd like to have it end the absorb stage based on the end amps measured by the FlexNet DC - which hopefully compensates for what is being pulled out via the inverter, if I understand correctly. I get that this won't be perfect, but hopefully it would be slightly less of a crapshoot than just putting a time limit in.

Unfortunately, nothing that i've found so far in the manuals explains the relationship (if any) between the "return amps" that you configure for the FlexNet and the End Amps value that you set for the CC itself. Is there a way to make the CC go into float based off the value from the FlexNet? Or am I just stuck with trying to approximate the background load and/or putting a time limit in?

Cheers,

Lucian

Dave Angelini · June 2016

I think that Outback end amps is good but it has been a long time for me. I know Schneider measures it accurately. Get a clamp-on meter and measure it near the end of absorption. That is the only accurate way besides the measuring SG.

vtmaps · June 2016

The outback controller can use end amps (return amps). There are two ways... if you have a flexnet DC you can base the end amps on the actual battery current (best way). If you don't have the flexnet, the controller can use its output as a measure of end amps, but the controller output is not the same as the battery input unless there are no loads and no other charging sources.

--vtMaps

herodotus · June 2016

Hi Guys,

Thanks for the responses, I understand that the FlexNet DC can measure the actual battery current - what I was looking for was some Outback-specific guidance on the correct configuration to make sure that the FM80 uses the value measured by the FlexNet to terminate charging rather than its own current measurement. At the moment I can't find anything conclusive in the manuals. There's an advanced setting for the FlexNet called "Enable Charge Termination Control", but the description says "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). Not sure if this is just bad wording or whether this setting really does only apply to inverters and not charge controllers.

Do I need to head over to the Outback forums to get an answer to this?

Cheers,

vtmaps · June 2016

herodotus said:
Do I need to head over to the Outback forums to get an answer to this?

That would be a good idea. Their forums contain voluminous material on the flexnet. There is a way to get all the controllers and inverters to go to float, but I don't have a flexnet and can't guide you. Have you seen this document (attached)?

--vtMaps

herodotus · June 2016

vtmaps said:
That would be a good idea. Their forums contain voluminous material on the flexnet. There is a way to get all the controllers and inverters to go to float, but I don't have a flexnet and can't guide you. Have you seen this document (attached)?

--vtMaps

Yeah, I've seen that document and I'm intending on following it - the only thing I was really looking for was clarity on whether the FNDC can really control the transition from absorb->float on the FM80 given the wording of the manual which somewhat suggests otherwise. I've found various topics skirting around the subject on the outback forums but nothing conclusive. Waiting for my registration to be approved there so I can ask directly....

Cheers!

Dave Angelini · June 2016

Sounds like you have AGM batteries? I would be very concerned with them! Make sure if there are multiple controllers that they all are networked so that the absorb voltage does not spike above the set-point.

herodotus · June 2016

No, I have Rolls S605 flooded lead acid batteries, and only one FM80. I'm keen to get the absorb timing running based on the end amps reading from the FLEXnet DC, and I believe that this *should* work, it's just that the wording of the manual has me a little worried. I'm aware that I'll need to calibrate this by comparing the SG readings and making sure it's still actually charging the batteries fully, but it seems like it would be a more accurate way of setting the absorb time than just putting a time limit on it that takes no account of the actual charge state of the batteries.

Vic · June 2016

Hi Lucian,

Am certain that you have seen the FNDC Topic on the OB Forum. There does appear to be some general disappointment with the functionality of the FNDC, there. Just in case, here is a Link:
http://www.outbackpower.com/forum/viewforum.php?f=28

I Agree, that EA is a very good way of ending Absorb, and have used EA, for over a decade on all systems here -- first with the OB MX-60s, and now with MidNite Classics and the WBjr current monitor, paired with the Classics. Just needed to tweak the Vabs and EA settings, quite recently, due to battery aging.

Good Luck, Vic

Dave Angelini · June 2016

herodotus said:

No, I have Rolls S605 flooded lead acid batteries, and only one FM80. I'm keen to get the absorb timing running based on the end amps reading from the FLEXnet DC, and I believe that this *should* work, it's just that the wording of the manual has me a little worried. I'm aware that I'll need to calibrate this by comparing the SG readings and making sure it's still actually charging the batteries fully, but it seems like it would be a more accurate way of setting the absorb time than just putting a time limit on it that takes no account of the actual charge state of the batteries.

Ok Flooded, you are overthinking this then. Even if you are off on the exact time for the battery to finish charging it is not a big deal.
I am not saying that this is something to gloss over but it is the biggest advantage of flooded! You can measure SG and slight overcharges of voltage and time are not going to be a problem. Keep water above the plates, do your EQ's and keep the tops clean and you will be in the cat birds seat for many years.

Outback FM80 End Amps vs FlexNet Return Amps

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