Solar Outback FlexMax 80 SHUNT?

[Pelagic]

I already have a Victron Shunt installed for my Victron smart monitor that provides me with all the data I need on the 24v house bank.

My FlexMax 80 solar controller did not come supplied with its own Shunt and the online manual is vague about its need

Same with the Outback Forums on Shunts. Some say no need, some say yes for additional Data for the controller.

Thier simple drawing shows a Shunt but not a smart monitor

So, can I assume that I can connect without the dedicated Shunt shown if I am using the Victron smart monitor.
(My last question before connecting)

[44'cruisingcat]

I have a Flexmax 80, no shunt.

[Pelagic]

Thanks 44cruisingcat.

This is my first Solar, so its a bit confusing as I was trying to figure out how it knows the current flow to the battery without one?

Do you get all the Data of performance without using one?

Trying to understsnd......Is it fair to say that the Outback is just like some fancy programmable "regulator" that converts the PV power to your battery specs and internally calculates output to batteries.

What is confusing me....I would have thought if it needed its own shunt, they would have supplied one?

[a64pilot]

I had my flexmax 80 for a year or two with no shunt. Although I admit I haven’t gotten into the data much.
However there is I assume an internal shunt, or other device to measure current, or how does it know output current?

[motion30]

The outback controller gives quite the volume of data. I'm just curious what more information would you like to have From a controller ?

[Zil]

Looking at your diagram, if the controller needed the shunt, there would be a feed back circuit from the shunt to the controller. they show the shunt to instruct about where to tie the controller negative.

[noelex 77]

The FlexMax 80 does not need an external shunt.

However, it will terminate the absorption phase more accurately if it knows the net current into the batteries. To do this it needs another black box called the Flexnet DC together with a shunt. I think it also needs a display (called a “Mate”) for the system to work.

The shunt will not function on its own. At least that is my recollection, check with Outback before you buy anything.

The FlexMax, Flexnet DC and Mate together form a sophisticated system that is overkill for most boat owners, but it very adjustable and will charge the batteries very accurately. It also works well as a battery monitor.

[a64pilot]

Interesting.
I have a Mate remote control. Is it possible to use my existing shunt with the Flexnet DC. I assume you wouldn’t want two shunts in series.

Just looked it up, it’s not cheap and doesn’t really seem to add all that much data that you don’t already get with the Mate.
What I would be looking for is a device that would hold absorption voltage until a user adjustable set point is reached, then drop to float.

[noelex 77]

Shunts in series are OK, but if the resistance of the existing shunt matches the Outback model (sometimes different resistances are programmable) you can use the existing shunt. Shunts are not expensive. Most of the cost is in the black boxes that convert the shunt measurements into meaningful data.

[mvmojo]

Been using the Outback Flexmax 80 for several years now - no shunt. It has been working great. 10 6v GC batteries for the house bank & 1,000 watts of panels. Left the boat for 6 months this winter, set the absorption to 13.4 v for 2 hrs & float at 12.6 v. When we came back to the boat, the batteries were 100% charged and didn't need a drop of water in any of the 30 cells! Batteries are 8 yrs old and still going strong thanks to the "gentle" nature of solar charging!

[Pelagic]

Originally Posted by noelex 77

The FlexMax 80 does not need an external shunt.

However, it will terminate the absorption phase more accurately if it knows the net current into the batteries. To do this it needs another black box called the Flexnet DC together with a shunt. I think it also needs a display (called a “Mate”) for the system to work.

The shunt will not function on its own. At least that is my recollection, check with Outback before you buy anything.

The FlexMax, Flexnet DC and Mate together form a sophisticated system that is overkill for most boat owners, but it very adjustable and will charge the batteries very accurately. It also works well as a battery monitor.

Thanks all for confirming that the shunt is not necessary.

What I researched on Outback Forums, only confused me further as they were for more sophisticared house installations with the added Flex equipment, Nolex notes.

Even the RV ones seemed to require morr


Thanks Nolex for simplifying for me. I can now make final connections today as i move onboard in June.

FYI, I mounted the Outback in plain view in the pilot house so that I can monitor performance
Not sure how noisy it is, but it is beside the drawer fridge whose compressor makes a bit of noise anyway.

[a64pilot]

I have never heard mine, but it’s mounted behind a Settee cushion, reason I got the Mate. Mate is stupid easy to install, just a phone plug. But I don’t know what else it gives has I never used my Outback 80 without it. I think it’s not much more than a remote screen

[BruceS]

On my boat the Mate is needed to read and adjust anything on the Outback inverter/charger. (at the helm) There are no controls or knobs on the inverter at all.
My solar controller is a separate unit that has it's own readout/controls/adjustments.
It's a Schneider Conext MPPT 60 150.
Both the inverter & the solar controller have their own battery temp monitor.

[mitiempo]

Originally Posted by mvmojo

Been using the Outback Flexmax 80 for several years now - no shunt. It has been working great. 10 6v GC batteries for the house bank & 1,000 watts of panels. Left the boat for 6 months this winter, set the absorption to 13.4 v for 2 hrs & float at 12.6 v. When we came back to the boat, the batteries were 100% charged and didn't need a drop of water in any of the 30 cells! Batteries are 8 yrs old and still going strong thanks to the "gentle" nature of solar charging!

Off topic but 13.4 absorption and 12.6 float are the strangest voltages I have heard of.

[44'cruisingcat]

Originally Posted by Pelagic

Thanks all for confirming that the shunt is not necessary.

What I researched on Outback Forums, only confused me further as they were for more sophisticared house installations with the added Flex equipment, Nolex notes.

Even the RV ones seemed to require morrAttachment 169614
Attachment 169615

Thanks Nolex for simplifying for me. I can now make final connections today as i move onboard in June.

FYI, I mounted the Outback in plain view in the pilot house so that I can monitor performance
Not sure how noisy it is, but it is beside the drawer fridge whose compressor makes a bit of noise anyway.Attachment 169616

The FM80 is completely silent unless the fan kicks in. With our solar panels configured to 24 volts, this rarely happens. When they were set up for 48 volts, the fan would run quite often on warm days.

The fan is a bit loud, similar to a hair dryer.