WhizBang Jr and Another Shunt Occupying Same Battery Cable

[finalman]

OK so I'm wanting to know if two shunts can occupy the same battery - cable without causing inaccuracies to each others readouts.

Reason I ask is I have the WBJr which I want to use to end the absorb cycle of the classics and the other shunt NOT a WBJr to monitor the battery health and capacity.

So I want the other brand shunt located nearest the battery - terminal on the cable and the WBJr before the loads at the other end of the cable.

I'm assuming this wouldn't create issues but just thought I'll ask just encase it does.

[dgd]

Most battery monitors use the standard Deltec 500amp 50mv shunt, the same one the WBjr uses.
For example the industry standard Bogart Engineering BMs use this same shunt.
As posted in other threads you can use the same shunt for both the WBjr and to connect the sense leads to another monitor

Personally I do not see the need for a separate BM as all the expected BM functions are provided by the WBjr and reported on the Classic screen, such as State or Charge% (Soc), Amp hours remaining, Net Amp hours, battery voltage (Classic measures this quite accurately)

dgd

[Cniemand]

I agree with DGD. The WBjr does all of that and seemlessly works with the Classic and the Local app to show all of that data. Also, it allows the Classic to see all that data and be able to upload it to the MyMidnite website for logging your data to be broken down later.

A second BM wouldn't give anything additional to your overall system

Cloud

[zoneblue]

And in case the obvious needs saying, you definately dont want to put two shunts in parallel, as that will alter the resistance of the shunt, and make both monitors read wrong. Also two shunts in series unnecesarily increases the the combined resistance of the shunts. But its not tragic, one deltec 500A shunt is about equal in resistance to one foot of 0 AWG. As dgd said one shunt is best so long as they are both 500A 50mV shunts. You may need an extra washer or two to make the extra terminals fit, but both devices are reading high impedence voltage only, and you could have 10 monitors on the same shunt happily enough.

[finalman]

OK guess I'll just use the MidNite shunt only then.

Here's my setup so far but still a long way from being done though:

Solar Board:


WBJr and Battery Cable Entry and Fuse Block:

[zoneblue]

Looks like your having a lot of fun putting that together.  Many of us did something similar initially, but with the benefit of hindsight the MNDC can save a lot of fuss: http://www.midnitesolar.com/productPhoto.php?product_ID=75&productCatName=&productCat_ID=8&sortOrder=4&act=p

[Cniemand]

Zoneblue : I have the MNDC175. works great. It is nice having a clean box with all your breakers.

[zoneblue]

Especially when you realise the awsome fault current potential of your typical off grid battery bank. Thousands of amps is not something you will ever get from your mains AC.

[Cniemand]

Exactly. Lithiums will happily dump all that embodied potential up if you ask it. :-D

[zoneblue]

Yep! Better ask nicely, or not at all.

[BobWhite]

I think that some nice work you've got going there!