Dual battery Voltage Meter

I use a Jaycar meter, lcd readout, does the temperature too. Provides alarms when the voltage is over or under a pre-set range. I've wired it to the 2nd battery, but 10seconds after starting they are running in parallel and therefore both batteries have the same voltage. Jaycar have a good range of meters available, all at good prices. Mine was about $35.

Cheers
Andrew

Just installed in the cab the device that Andrew describes above with a switch to flick between the two batteries.

In the back of the ute I have a little wooden junction box which includes a fuse box inside and have installed a LCD panel meter available for $10 from Dick Smith. You'll need to be handy with a soldering iron as it involves installing two onboard resistors and soldering a jumper wire. It can't power from the supply it is measuring without adding further electronics but can be powered from a 9 volt battery, draws only 1ma so it will last a long time. Then it's just a matter of calibrating the device. This option may or may not be for you.

DSE cat no is Q222O

Jaycar have a LCD panel meter that is all setup as a volt meter out of the box. I think it was between $30 and $40... I didn't take this route as the previous was cheaper for me.

Dear Alan
I added a 3 LCD display to the T-Van showing current into / out of
the battery, battery voltage and car battery voltage.
I will post a photo If someone can suggest where It can be placed.
I has turned out well and the digital display makes it much
easier to keep track of what's happening with the batteries.
It was constructed to with 3 digital panel meters from Dick Smith,
scrap aluminium and teak.
I will post a photo If someone can suggest where It can be placed.

Cheers John

Alan,

I use one of the Jaycar jobbies. Only reads one voltage though.
Unit comes with a ciggy style plug. As I have a socket in the cab from my second battery to run the GPS etc. from, all I do is swap the plug from one socket (main battery) to the other (second battery) as required, to monitor one or the other.

I don't usually bother with the main battery while traveling as I trust the isolator to do its job, but the option is there anyway.

I mounted the meter to the console using adhesive backed velcro so I can remove it if I desire.

I bought one of those 12V battery testers from Dick Smith ~$19, which has 5 different coloured LEDS that show the state of charge. It comes with aligator clips. I cut these off & installed a small slider DPDT switch into the unit. Then I wired both batteries to the unit. I just move the slider switch between Main & Aux battery. I mounted the unit under on the ventilation ducting.
Sparky

Alan,

We use the Jaycar voltmeter/clock/indoor-outdoor thermometer referred to by others above. I bought in online from Jaycar for about $40. It's a great little gadget and apart from monitoring your batteries, the thermometer provides a bit of interest as it not only gives current indoor and outdoor temp, it also stores max and mins for previous 24hrs so you can see exactly how hot or cold it got.

The gadget is really designed for monitoring your main battery through a ciggy lighter plug. Following the suggestion of many others on this forum, we cut off the ciggy plug and hard wired it to a 3-way switch direct wired to our batteries. With the flip of the switch we are now able to monitor our main, aux and trailer batteries.

:o) Melissa

Thanks everyone for your replies, I'll go away and investigate some more but I am a lot closer to a workable solution now.

Great forum,
Thanks

Here is pic of one I made from a jaycar kit. The kit is for a led bar graph voltage meter. It costs about $14 and is very simple to make (about 6 components). I simply squeezed two of the kits into a small case, instant dual battery monitor!

Link here

May I just drop in a word of caution regarding battery voltage measurement.

It's fine for starter batteries - but can be close to meaningless with deep cycle batteries.

The charging and discharging process of lead acid batteries is an electro-chemical reaction between the lead plates and the water/acid electrolyte. Because deep cycle batteries have very few but thick plates there is much less surface area than the multiple, thin plates of starter batteries - hence there is one hell of a lag between charging or heavy discharging and that charge being absorbed or offered up by the electrolyte.

Thus, when one takes a voltage measurement all you are measuring is the 'charge on the plates'. This can be hugely misleading (as the time lag is 24 hours or so.)

An almost flat deep-cycle battery will show as close to fully charged after a couple of minutes on a fast charger (but will still be only barely charged). A fully-charged deep cycle battery that has run a microwave for a couple of minutes (typically 110 amps at 12 volts) - will show as close to flat - when it's still well charged.

Because of the above a great many people draw totally wrong conclusions about their battery's state of charge.

Summarising - fine for starter batteries, but for deep cycle batteries almost meaningless unless the battery has rested for many hours - at least overnight.

If you are interested there's a heap more about this on my website.
Collyn Rivers

Hi Alan. I went the Jaycar route and as others have said use it to measure aux and main battery by swapping plugs. I use the outside temp guage to measure the temp inside the engel. It serves me well as insurance against loosing a couple of weeks of tucker if the fridge power fails or temps get higher than I want. Cheers

John send me a pic of his metering system he built for the T-Van...as discused above.....nice work John

Meters