Cheap Battery monitor.

[megatexture]

I would concur with Megatexture's reply. 30A doesn't leave a lot of leeway once a few things are switched on ..... but of course it depends what accessories you have (or may add in the future).

MT, there is a pic of the shunt in the ad linked to in the OP.

Same seller also has similar rated to 200A if required, but 100A would suit most camping set ups.

Thanks mate ill have another look must have missed that pic

[sooty_10]

Not that I am aware of. If you were planning to run a winch off the battery(s) being monitored going for the 500amp one would save having to bypass/reset the monitor as I have to do with my 100A monitor.

My aux battery is earthed to the chassis and also has a direct earth to the start battery, with this shunt on the negative side would it simply display the complete vehicle battery (ie. both batteries) capacity?

I also have 6 B&S twin core going from the aux batt to the rear of the vehicle to a distribution fuse block and earthed to my rear drawers with a stud for easy earthing of rear accessories. I'm just trying to get my head around where the best spot for the shunt would be, and if it actually makes a difference to what it reads/sees in terms of amps etc.

If I put the shunt inline with the 6 B&S negative, it would be pointless having a higher amp shunt than the capacity of the cable?
Or do you simply place the shunt in the biggest negative cable attached to the battery, such as chassis earth cable?

[Cuppa]

My aux battery is earthed to the chassis and also has a direct earth to the start battery, with this shunt on the negative side would it simply display the complete vehicle battery (ie. both batteries) capacity?

I also have 6 B&S twin core going from the aux batt to the rear of the vehicle to a distribution fuse block and earthed to my rear drawers with a stud for easy earthing of rear accessories. I'm just trying to get my head around where the best spot for the shunt would be, and if it actually makes a difference to what it reads/sees in terms of amps etc.

If I put the shunt inline with the 6 B&S negative, it would be pointless having a higher amp shunt than the capacity of the cable?
Or do you simply place the shunt in the biggest negative cable attached to the battery, such as chassis earth cable?

Firstly, this is testing my level of understanding so don’t take what I say as 100% gospel.
Secondly without seeing a wiring diagram of your setup giving answers to your question is difficult for me. Others more knowledgeable may be clearer.

However:
I think that if all the negatives to aux battery are connected to one side of the shunt , with the other side of the shunt connected to the Aux battery neg terminal, then the battery monitor could function fully (ie. show real time voltage, amps in & amps out, plus State of Charge % for just the aux battery. This assumes that you have nothing which draws current from directly both batteries. (i.e. a positive cable to the same accessory from both batteries - highly unlikely).

In terms of what amperage monitor to get....... it should be enough to cover the combined amperage of everything that is powered off the aux battery which could be used at the same time. Thus you need to know the max current draw of each accessory.

If anyone can confirm or correct what I’ve said I’d appreciate it.

[megatexture]

And also Included in the accessories on the aux batt would be the alternator amps if using an isolator or max Amps output of your dc dc charger, but for the price just go the 500amp unit.

I've just ordered a 100a one also but this is only for the camper so the larger unit isn't necessary.

[sooty_10]

Wiring diagram.jpg

Not sure if that pic works but this is a basic layout of my vehicles current wiring setup. I have most of my accessories currently running off the rear fuse block, but have a couple to go on the engine bay one. Where would be the best spot for the shunt? Or do I need to isolate the earths for the Aux battery from the chassis, and have all accessories only earth to the battery? My Winch is running from the main battery with the winch solenoid pack power coming from the aux batt fuse block, I would like to setup an override for the DBI to enable the winch to use both batteries, and for jump starting but that is another whole kettle of fish.

[sooty_10]

I've just done some googling and trying to understand the shunts I'm assuming they are a directional device? ie, there is a specific direction they need to be installed in with a load side and a battery side? If so with my above setup I believe if I install it directly on the negative of the battery and have all earths then come from the shunt, including the chassis earth it should work? My only other query is if all else is correct is would I need to remove/isolate the accessories earths, or can they still utilise chassis earthing?

[sooty_10]

Firstly, this is testing my level of understanding so don’t take what I say as 100% gospel.
Secondly without seeing a wiring diagram of your setup giving answers to your question is difficult for me. Others more knowledgeable may be clearer.

However:
I think that if all the negatives to aux battery are connected to one side of the shunt , with the other side of the shunt connected to the Aux battery neg terminal, then the battery monitor could function fully (ie. show real time voltage, amps in & amps out, plus State of Charge % for just the aux battery. This assumes that you have nothing which draws current from directly both batteries. (i.e. a positive cable to the same accessory from both batteries - highly unlikely).

In terms of what amperage monitor to get....... it should be enough to cover the combined amperage of everything that is powered off the aux battery which could be used at the same time. Thus you need to know the max current draw of each accessory.

If anyone can confirm or correct what I’ve said I’d appreciate it.

Cuppa thanks heaps. I read your post and didn't quite put two and two together then after I did some googling and drew my diagram I happened to re-read your above comments and it all made sense. I need to put the shunt on the negative of the battery I want to monitor and have all earths come from the shunt. Time to order.....

[Cuppa]

I think you’ve got it Sooty. I would do as MT suggests.

Seems there are different types of shunt for different purposes just to confuse things, but in our case we are talking about a shunt for measuring current.

An ammeter shunt allows the measurement of current values too large to be directly measured by a particular ammeter. In this case the shunt, a manganinresistor of accurately known resistance, is placed in series with the load so that all of the current to be measured will flow through it. In order not to disrupt thecircuit, the resistance of the shunt is normally very small. The voltage drop across the shunt is proportional to the current flowing through it and since its resistance is known, a voltmeter connected across the shunt can be scaled to directly display the current value.

from http://en.wikipedia.org/wiki/Shunt_(...rent_measuring

A diagram from my Nasa BM1 ‘Compact’ Manual, showing the shunt installation.

screenshot_159.png

Your diagram + shunt

[sooty_10]

The monitor display unit.
image-1258715294.jpg

The shunt (500A) is huge, bigger than I was expecting.
image-3787965957.jpg

image-2407775442.jpg
The instruction diagrams, it also came with a little booklet.
image-2765282366.jpg

[MuddyTroll]

Wow is massive! Think I'll go the 100A..