Dual Battery Monitoring

Submitted: Thursday, Apr 24, 2014 at 15:52
ThreadID: 107438 Views:2320 Replies:5 FollowUps:6
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Hi there, just wondering if anyone can give some advice on battery monitoring ? I have a dual battery set up in my Prado, using a Sure Power Battery Separator. This seems to do the job well . I run usually an engel and lights on the system. However I have no idea how much is left in the axillary battery until the engel stops working.
Recently I used a solar panel whilst camping at Ningaloo. Worked well , except I was guessing as to how the batteries were travelling.
Is there a monitor I can set up to know exactly how much charge the batteries have?

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Reply By: Mick O - Thursday, Apr 24, 2014 at 16:18

Thursday, Apr 24, 2014 at 16:18
Mike the options are endless. From a simple digitale volt meter from Jaycar for $14 through to multi function amps/volt metres from Autron, VDO etc.

Have a look at some of Derek Bester's stuff at ABR Sidewinder. He is a business member on the site. There will be something fit for purpose there that will not break the bank.

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AnswerID: 531120

Follow Up By: Member - PJR (NSW) - Thursday, Apr 24, 2014 at 17:42

Thursday, Apr 24, 2014 at 17:42
As Mick O said maybe a simple digital monitor.

We have two Engel fridges and I have setup one of these on each. I got into the circuit board and picked a suitable 12 V line that gave me the input voltage to the fridge. After all isn't that the most important one.

This meter also comes with a clock (dunno why) and a temperature sensor. Wired one to each fridge and stuck them on the outside of the fridge where I could easily see them from the outside of the car. Each cost $4.19 and postage was $6.


Digital meter on ebay.

FollowupID: 814144

Follow Up By: Gnomey - Thursday, Apr 24, 2014 at 18:57

Thursday, Apr 24, 2014 at 18:57
Phil. A question if I may. Do know if these things have an internal battery? The blurb wasn't too clear. My reason for asking is I'm looking for something like to monitor temperature in a coffee machine and I'd rather not have to muck about with a 12v power source.

FollowupID: 814150

Follow Up By: Member - PJR (NSW) - Thursday, Apr 24, 2014 at 21:11

Thursday, Apr 24, 2014 at 21:11
They need 12V mate. Actually I think that bthey work on a 5 to 30VDC supply.

This one works on LR44 batteries at a low 1.5V and would last for ages.

There will be more. Try searching for "digital thermometer"

eBay Digital Thermometer.


FollowupID: 814159

Follow Up By: Gnomey - Thursday, Apr 24, 2014 at 22:28

Thursday, Apr 24, 2014 at 22:28
Thanks mate. Shame about the 12v. I've seen a few like the one you linked to but in the way of these things what I want seems to be a unusual range ie up 100c - not a common temp in fish tanks and reptile cabinets. :)) Will keep on looking. Thanks again.

FollowupID: 814163

Reply By: Bludge - Thursday, Apr 24, 2014 at 16:23

Thursday, Apr 24, 2014 at 16:23
There are heaps of monitors out there, have a look at ABR Sidewinder, there is a good stock of meters, guages and battery monitors available.
AnswerID: 531121

Reply By: Robin Miller - Thursday, Apr 24, 2014 at 20:43

Thursday, Apr 24, 2014 at 20:43
Hi Mike as per other replies lots of option including quite complex ones , but I tend to reccomend simple plug in cig socket voltmeters as good value for money.

There are a number of items out there some similar to this item , some on ebay and some from $3.

I reccomend this one because I have measured there accuracy over a temperature range and know that they give repeatable results.

Note - Itmes like this should take there feed from close to battery so that the voltage read doesn't change a lot under load.


Jaycar CAT. NO. QP2220

RRP $19.95

Cigarette Lighter Battery Monitor
Check the voltage output of your car's battery quickly and easily. Simply plug this handy voltmeter into the cigarette lighter socket and get an instant readout of the electrical system's voltage.Specifications:Display resolution: 0.1VAccuracy: +/- 2%Operating voltage: 8 - 28VDC more...

1+ $19.95
5+ $17.70
10+ $15.70
Enter Quantity -

Robin Miller

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AnswerID: 531135

Follow Up By: ABR - SIDEWINDER - Friday, Apr 25, 2014 at 08:52

Friday, Apr 25, 2014 at 08:52

On special this week. : Newsletter-ABR

FollowupID: 814169

Reply By: Member - Chris_K - Thursday, Apr 24, 2014 at 22:24

Thursday, Apr 24, 2014 at 22:24
...or you could check out one of these. Not cheap (couple of hundred $'s) but they work well. We have one in the camper trailer...takes the guess work out completely:



AnswerID: 531141

Follow Up By: Echucan Bob - Thursday, May 01, 2014 at 15:41

Thursday, May 01, 2014 at 15:41
Yes I'll vouch for Nasa. I have the Clipper battery monitor.
FollowupID: 814619

Reply By: The Bantam - Thursday, Apr 24, 2014 at 22:27

Thursday, Apr 24, 2014 at 22:27
Mike there is no such thing as a monitot that will tell you exactly how much is left in your battery.....some will try and tell you otherwise, but that is BS.

Batteries simply do not work like that....they are not a tank or a bucket.

How much energy that can be drawn from a lead acid battery varies greatly depending on a number of factors.
There is no device that can sucsessfully keep track of all those variables.

variables such as
How well the battery has been charged...there is an over simplistic view of that alone.....you could occupy a whole thread about this matter alone.

The age and condition of the battery..including its recent charge / discharge history.

Temperature can produce wild variations in battery performance.

The amount of current drawn varies the capacity available.

Yes there are monitor systems that make some attempt at tracking capacity and use.......and there are a lot of people that believe they are accurate..they are mistaken.

BY far the best option is a digital volt meter...it wont give you an exact remaining capacity but it will give you a charge indcation....and that is about the best you can hope for.

AnswerID: 531142

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