Q for the Outback Tech's: FM80's Terminal AMP Ratings?

Discussion about the FM100, FM80, and FM60 Charge Controllers

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Surfpath
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My RE system: Outback Flexpower-1-6 system (VFX3048e, FM80, 48v, 50hz, 240v), 2,750w of PV (4 series of 3 panels/ea, 100v max-combiner to controller), 370amp/hr L16REB battery bank. Honda 2k briefcase generator. 100% offgrid.

Q for the Outback Tech's: FM80's Terminal AMP Ratings?

Post by Surfpath » Fri Jan 30, 2015 7:54 am

I have a quick tech related question.

I am trying to determine if my current combiner to FM80 wire run is appropriately sized for a proposed PV expansion. My current run of #6 AWG ANCOR Boat Cable with (105 degree C insulation), technically can carry higher current than typical #6 AWG (rated at 60 degrees C). However that seems to be dependent on IF the terminal connectors in a) my Midnite combiner box and b) my FM80 are also rated at a higher temperature than the usual 60 degree C connector.

So my question is for the Outback Tech Team, what is the termination temperature rating for the FM80 PV + & - in terminations). Are they 60 degrees C or 75 degrees C rated, or something different??

This technical bulletin from Cooper Bussman explains exactly what I am referring to:
http://www.cooperindustries.com/content ... cities.pdf
Thanks!

ps. I'll ask Midnite the same questions. let's see who answers first.:-)

Vic
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Re: Q for the Outback Tech's: FM80's Terminal AMP Ratings?

Post by Vic » Fri Jan 30, 2015 9:01 am

Hi Surf..,

Generally the limiting factor in current carrying capability are the terminals on circuit breakers, and perhaps fuses.

Cannot speak directly about the thermal rating of the FM CC input and output terminals, but almost all circuit breakers have a maximum rating of 75 C for connections, and this is often the limiting factor, even if the cable used is rated at 90 or 105 C.

Am not an OB Tech person, the above is just what I have read. FWIW, Vic
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Kurt Lundquist
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Re: Q for the Outback Tech's: FM80's Terminal AMP Ratings?

Post by Kurt Lundquist » Tue Feb 03, 2015 7:32 am

The FM manual says you should use copper wire rated at 75┬░C or higher. I think you can safely assume at least a 75┬░C rating for the FM80 terminals. Controller accepts up to 2 AWG. FM80 maximum ISC input is 64 amps at STC. I am not sure if "ANCOR Boat Cable" is listed for PV applications so I cannot comment on that. Since you have a 48 volt battery bank I'd be surprised if you were able to parallel an array that would come close to the 64 amps ISC input rating. You will need at least 2 (72 cell) but more likely 3 (60 cell) modules in series in order to get the proper input voltage to the controller (for a 48 volt battery the PV VMP should be >70 and <125 as a general rule of thumb). If you have proper over current protection in place the main input wiring issue will be voltage drop.

Here is a link to the FM manual http://www.outbackpower.com/downloads/d ... manual.pdf
I found the info quoted above on pages 7 & 10. The sticker on the side of the FM lists this info as well.

-Kurt
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Surfpath
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My RE system: Outback Flexpower-1-6 system (VFX3048e, FM80, 48v, 50hz, 240v), 2,750w of PV (4 series of 3 panels/ea, 100v max-combiner to controller), 370amp/hr L16REB battery bank. Honda 2k briefcase generator. 100% offgrid.

Re: Q for the Outback Tech's: FM80's Terminal AMP Ratings?

Post by Surfpath » Tue Feb 10, 2015 3:59 pm

klundquist wrote:The FM manual says you should use copper wire rated at 75┬░C or higher. I think you can safely assume at least a 75┬░C rating for the FM80 terminals. ...but more likely 3 (60 cell) modules in series in order to get the proper input voltage to the controller (for a 48 volt battery the PV VMP should be >70 and <125 as a general rule of thumb). If you have proper over current protection in place the main input wiring issue will be voltage drop.
Hi Kurt,
Many thanks for that bit of research. By the way I do have a "three 60 cell panel" set up (three strings of these presently, 9 in total). I'm about to add a 4th string in a month, & wondering if I can add a 5th in the future.

With the 3 strings now I see a typical max of ~35 amps on the FM80 (sunny day). With the new string I'll expect to see 47 amps, and with a fifth string ~59.

I am pretty confident now that my fourth string will be fine, current-wise. The terminals on my Midnite combiner box are rated at 90 degrees, the Ancor boat wire 105 degrees, and (like you mention) the Outback FM80 terminals will be rated at 75┬░C. So this should confer a slightly higher ampacity that the typical 60┬░C wire max rating of 55amps. I'll see later about the 5th string :grin:

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Re: Q for the Outback Tech's: FM80's Terminal AMP Ratings?

Post by gww » Tue Feb 10, 2015 4:59 pm

surf path,
You must have a fairly short run with 6awg wire, every time you ad more amps you voltage drop will be greater. I don't know if there is a point of diminishing returns on how far you can go. The amps you gave for your strings now are, I am assuming, Your cc output amps and not what is running on your wire. I currently have a simular syatem with four simular strings, at some point I intend to put 2 more. I think the cc is good for about 4000 watts and I will have about 4200 watts. It is the output amps that can only go to 80 amps and the cc will start limiting, if it gets hot it may limit below its rating. I would say panel wise 5 strings is no problim but if I were you I would check my 6 awg wire with the panels acumulative amps voltage, not the cc's output voltage, with a volt drop caculator.
gww

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