Cheap Battery monitor.

[Cuppa]

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.

[Bloodyaussie]

Worth a punt at that price...

[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.

[Family4x4]

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

[megatexture]

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.

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

[megatexture]

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

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..

[Cuppa]

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

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.

[megatexture]

It would be able to switch for volts

[Cuppa]

I would be able to switch for volts

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).

[megatexture]

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

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