Cheap Battery monitor.

http://www.ebay.com.au/itm/180957166...84.m1423.l2649

These look like a useful bit of gear. Monitors that do what this one does usually cost $200 to $400.

Comes with the shunt & shows voltage, amps in & amps out, battery percentage (State of Charge), time to full charge (at current charging rate) & more.
In fact it does all that my NASA BM1 ‘Compact’ monitor does which I bought at a bargain price of $140 (usually closer to $240).

I have no direct experience of these units but do know of one person who is using one successfully & he is not someone likely to accept rubbish.

Worth a punt at that price...

Well spotted Cuppa. Since i'm doing my dual battery system as I type this, I was after something like this. Hmmm Buy button is.... tempting.

Thanks Cuppa would this unit be able to monitor both batteries? Would it be as simple as adding a switch if it doesn't?

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Originally Posted by Hodge

Well spotted Cuppa. Since i'm doing my dual battery system as I type this, I was after something like this. Hmmm Buy button is.... tempting.

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Do it mate one of us has to be the Guinea pig lol I'll be curious to see how it goes

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Originally Posted by Family4x4Fun

Thanks Cuppa would this unit be able to monitor both batteries? Would it be as simple as adding a switch if it doesn't?

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The switch would probably depend on if when switching the unit between batteries it turns the unit off then you will have to reset the ah capacity of the batteries loosing your current place but it looks like there are two pos inputs so one may be for the amps reading and power and the other volt reading.

I think it would work looking at it closer.. But maybe put a momentary switch on the pos powering the shunt so you don't forget to switch it back..

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Originally Posted by Family4x4Fun

Thanks Cuppa would this unit be able to monitor both batteries? Would it be as simple as adding a switch if it doesn't?

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Not really. The way that these monitors are able to be used as a ‘Battery fuel gauge’ is by first the capacity of the battery being set by the owner. Eg. 100Ah. When the battery is full (determined by voltage) any usage draws Ah’s from it. The monitor can then tell how much of the capacity, as a percentage, has been used. Likewise it can add Ah’s when being charged.
They are smart enough to recognise charging & usage at the same time. It is not uncommon for my monitor to show +ve amps from the solar whilst the fridge is running for example, because there is more coming in than is going out.

The problem with switching between two different batteries is that each battery capacity would likely be different, meaning the monitor would need to be reset. Even if they were exactly the same it would still take a little while for the monitor to suss out the other battery’s SoC. So not really practical. Besides I can see no point monitoring a start battery in this way. As long as it has sufficient voltage to start the vehicle that is all that is needed, & most dual battery systems have a means of protecting against draining the start battery.

For setups with more than one aux batteries, this meter could monitor both if they were connected to each other (would see them as one large battery). If it is desired to not connect them together then a separate monitor for each battery would do the job.

It would be able to switch for volts

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Originally Posted by megatexture

I would be able to switch for volts

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Yes you could switch just for a reading of voltage & real time amps in or out, but could also achieve this with a simple volt/ ammeter. The same seller has such combo meters too.(& they are cheaper).

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Originally Posted by Family4x4Fun

Thanks Cuppa would this unit be able to monitor both batteries? Would it be as simple as adding a switch if it doesn't?

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What were you trying to achieve? Car dual battery or a camper setup ?

I'm tempted to get one just to see what its like lol . HMmmm

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Originally Posted by megatexture

What were you trying to achieve? Car dual battery or a camper setup ?

I'm tempted to get one just to see what its like lol . HMmmm

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Car dual battery. I have just started the install. I would be interested in something like this to be able to monitor the cars batteries.

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Originally Posted by Cuppa

Not really. The way that these monitors are able to be used as a 'Battery fuel gauge' is by first the capacity of the battery being set by the owner. Eg. 100Ah. When the battery is full (determined by voltage) any usage draws Ah's from it. The monitor can then tell how much of the capacity, as a percentage, has been used. Likewise it can add Ah's when being charged. They are smart enough to recognise charging & usage at the same time. It is not uncommon for my monitor to show +ve amps from the solar whilst the fridge is running for example, because there is more coming in than is going out. The problem with switching between two different batteries is that each battery capacity would likely be different, meaning the monitor would need to be reset. Even if they were exactly the same it would still take a little while for the monitor to suss out the other battery's SoC. So not really practical. Besides I can see no point monitoring a start battery in this way. As long as it has sufficient voltage to start the vehicle that is all that is needed, & most dual battery systems have a means of protecting against draining the start battery. For setups with more than one aux batteries, this meter could monitor both if they were connected to each other (would see them as one large battery). If it is desired to not connect them together then a separate monitor for each battery would do the job.

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My question about these is does the charge current from the alternator need to go through this meter (shunt?) to maintain the charged % etc as well as the items drawing power? If so not the best for dual batteries, ideal for portable power pack though.

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Originally Posted by Bloodyaussie

Worth a punt at that price...

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Yes it is... I have ordered one to put in my camper. We'll see what its like when it arrives...

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Originally Posted by MuddyTroll

My question about these is does the charge current from the alternator need to go through this meter (shunt?) to maintain the charged % etc as well as the items drawing power?

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Yes. Shunt is on the negative.

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Originally Posted by mudski

Yes it is... I have ordered one to put in my camper. We'll see what its like when it arrives...

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Will look forward to getting your feedback.

http://www.ebay.com.au/itm/DC-120V25...item27d29d0d45

This one looks the same as the OP posted, but it is cheaper with free postage. However it doesn't have an external shunt included, it does state that it has an internal shunt? Thoughts Cuppa.....

they are all from China

Only 30A, It wouldn't be suitable for heavy power uses, but I would like to see the shunt that comes with the link cuppa posted when you get it mudski:smiley_thumbs_up:

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Originally Posted by sooty_10

http://www.ebay.com.au/itm/DC-120V25A-Volt-Amp-Battery-Capacity-AH-Power-Combo-Meter-Charge-Discharge-Timer-/171037232453?pt=AU_B_I_Electrical_Test_Equipment&h ash=item27d29d0d45

This one looks the same as the OP posted, but it is cheaper with free postage. However it doesn't have an external shunt included, it does state that it has an internal shunt? Thoughts Cuppa.....

they are all from China

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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.

Yeah fair enough on the 30A internal shunt. I just realised that the ones I'm looking at are actually the same seller you posted up Cuppa :) He has them in 50A, 100A, 200A, 300A and 500A. All for about an extra dollar dearer than the last one. Is there any downside to going a larger, say 200A or 300A shunt?

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Originally Posted by sooty_10

Is there any downside to going a larger, say 200A or 300A shunt?

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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.

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Originally Posted by Cuppa

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.

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Thanks mate ill have another look must have missed that pic

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Originally Posted by Cuppa

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.

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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?

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Originally Posted by sooty_10

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?

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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.

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.

Attachment 47457

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.

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?

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Originally Posted by Cuppa

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.

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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.....

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.

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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.

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

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

Attachment 47464

Your diagram + shunt

The monitor display unit.
Attachment 47734

The shunt (500A) is huge, bigger than I was expecting.
Attachment 47735

Attachment 47736
The instruction diagrams, it also came with a little booklet.
Attachment 47738

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

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Originally Posted by MuddyTroll

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

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Yeah I'll see how I go fitting it up, but they do have shunts separately as well so might downsize if there is significant size difference and its difficult to fit up. From the pics on eBay it simply looked like the higher amps shunt had more black bars.

Testing the meter displaying volts and amps. Engel is on max temp empty, compressor running.
Attachment 47767

Shunt installed, excuse the very temporary wiring.
Attachment 47768

And with arb compressor and fridge both running full.
Attachment 47769

Showing volts and batt %
Attachment 47770

Got my 100 amp in the mail today :smiley_thumbs_up: can't wait to hook it up,has anyone tested how voltage drop would affect the unit? I'm looking at mounting the display about 4m away from the shunt.... I might have to do some testing if not

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Originally Posted by megatexture

Got my 100 amp in the mail today :smiley_thumbs_up: can't wait to hook it up,has anyone tested how voltage drop would affect the unit? I'm looking at mounting the display about 4m away from the shunt.... I might have to do some testing if not

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I was wondering this too, if I was going to rear mount my gauge in the cargo area. I guess it depends on the quality of wire used. How big does the 100A shunt compare to the pic I put up of the 500A?

Quite a difference lol I imagine yours is just 5 of mine same length and size yours is just taller as the black bars are mounted vertical mine are horizontal.

Looks like they are easy enough to connect up. Am looking forward to reports on user friendliness & accuracy (plus long term reliability down the track). Compared to the cost of alternatives they really do look like a bargain, & may even be the beginning of bringing down the price of the brand name alternatives.

Got mine but it won't be putting it in anytime soon. Plus I have to work out how to fit it.:)

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Originally Posted by Cuppa

Looks like they are easy enough to connect up. Am looking forward to reports on user friendliness & accuracy (plus long term reliability down the track). Compared to the cost of alternatives they really do look like a bargain, & may even be the beginning of bringing down the price of the brand name alternatives.

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As for user friendliness I have no idea about this stuff, and managed to follow the instructions and input the battery AH and set it all up. Accuracy I have no idea, I managed to set it so there was 0 amps been drawn with everything off, and then when I turned on the fridge I got 2.5A which is what Engel list as their maximum current draw, I had the fridge on max and it was warm inside when I started. Also when I switched on my compressor it was showing similar Amps to what ARB claim as well. I don't have an ammeter that I can double check against.

Fitted my shunt just now, a bit annoying but that's only because of my existing setup on the camper.

Too effing cold to go outside and play on my car or camper. Whats your thoughts megatexture on the kit? Good for the money?