Shunt, do I need one ?

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Shunt, do I need one ?

Postby Noah on Sun Mar 04, 2018 9:44 am

Hi everyone,
Since I'm new at this I have a new question. So for our RV system we bought an Outback Flexmax 60 controller. I read more and more on shunts, even on the owner manual there is one on the skematic but doesn't show where to hook it up.
I know that they get connected on the negative side but where on the controller ?, I'm I missing something here ?, Thanks
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Re: Shunt, do I need one ?

Postby jguzman on Sun Mar 04, 2018 12:08 pm

Shunts are typically used to measure current flow from dc sources / loads or used a common point of connection for multiple DC sources.
Here is a video that explains the use of shunts:

Noah wrote:I know that they get connected on the negative side but where on the controller ?

In this case it will connect to the BAT NEG or charge controller battery output terminal.

Jorge Guzman
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Watch easy to follow video tutorials:
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Re: Shunt, do I need one ?

Postby Mike Curran on Sun Mar 04, 2018 3:05 pm

I ran my first system, an MX60 connected to 1.44kw of PV, with 2 gvfx3524 grid-tied inverters and 1766Ah, 24V battery, for 10 years without any shunts in the system. In 2016 I added a Flexnet DC to realize some of its charge controlling and grid connection permissive features, and at that point I added 2 shunts, one for my MX60 and one for my 2 inverters. The FNDC needs shunts measuring current to function, as Jorge points out. And an FNDC also requires an Outback Mate controller to program and display. There are other makers of battery monitors similar to the FNDC that work without additional equipment. One that comes to mind is by Bogart Engineering called the Trimetric.

Here are links to both these devices: ... trics.html ... flexnet-dc Reading these should give you an idea about how the data from shunts might be useful to you.

But short answer is, you don't need a shunt for your system to operate. But if you install one you will need additional equipment to realize any benefits from the shunt(s).

- Mike
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Re: Shunt, do I need one ?

Postby SandyP on Mon Mar 05, 2018 7:07 am

On an RV I would think that some sort of battery bank monitor would be helpful.
We have used the Victron BMV-702 ( for a while now and find that when you have it set up properly it gives you a reasonably good idea of how much charge your battery bank has, and you can hook a second wire up to your vehicle starter battery and it will show its Voltage as well.
The Victron comes with a shunt which is required to "count" the charge amperes in and discharge out of the battery bank.
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