MICTUNING double voltmeter

[george_tlc]

George can we revisit the 24v bank usage. If I have digested correctly everything you have outlined I think it sums up something like this:

Pull the diode out.
Ground the gauge to the chassis.
Feed the gauge aux + leg with a center-tap.
Feed the gauge main + leg with switched 24v bank power.

Powered up the "main" reads total bank and the "aux" reads the lower battery.

I understood you to say that there is a continuous, albeit slight, current draw on the aux battery. Is that still the case here?

Dan, yes, what you describe is exactly how it would work. There is a 0.2mA continuous current draw from the AUX 'input' which is partly just the current draw for the sensing potential divider circuit on the board. That 0.2mA should not cause an issue with battery charge balance given there may be that much leakage just from battery posts and dirty battery case conduction paths...

cheers,
george.

 

[cruiserdan]

Dan, yes, what you describe is exactly how it would work.

A small miracle on my part.

Thank you as always George.

 

[jjohnny]

Thanks for the great information on this George. I like the looks of this and am wondering what the OP asked as well if this will fit in an 80 factory knockout spot? If it does I will your little diode removal and it will be just what I'm looking for.

 

[jjohnny]

Actually, nevermind, I did a little more searching and found out the info. Thanks.

 

[swankstar]

Just a heads up to anybody interested in these things, they have a new board that doesn't keep the power on. No need for @george_tlc 's mod any more.

 

[Joe Link]

You guys who have these care to share pics of them installed in your interior?

 

[thelal]

Just a heads up to anybody interested in these things, they have a new board that doesn't keep the power on. No need for @george_tlc 's mod any more.

Got more pics and link?

 

[icorradoi]

You guys who have these care to share pics of them installed in your interior?

This one is always on. Haven't had any issues and since it's not my daily, I like being able to just walk by and look at the battery voltages if it sits for a few days/weeks.

 

[mobi-arc]

Wish I knew the brand.

Found it: Dual Battery Volt Meter for Toyota Prado 150, Landcruiser 200, 2016 Hilux - Solid Kit

 

[swankstar]

Wish I knew the brand.

Found it: Dual Battery Volt Meter for Toyota Prado 150, Landcruiser 200, 2016 Hilux - Solid Kit

View attachment 2217883

that's NICE!

 

[swankstar]

Got more pics and link?

pics and link to what exactly? I used the same stuff as earlier in this thread, only the internals have changed.

 

[thelal]

gotya

 

[Greg_B]

Thanks for all the info on this gauge. I ordered one (and a couple of the dual USB's as they work from 12-30V) and have them installed in the BJ74. They do not fit the knockouts like a stock switch as each opening required some removal of material on the long sides (slight lip that is there) to fit. And they don't snap in place like the stock switches...but so far its all staying in place.

With the voltage gauge I used the engine bay power port to supply constant 24V power to the upper display and used the keyed 24V to trigger a relay that feds the lower battery + pole to the lower display. Used the constant 24V power to supply one dual USB and keyed 24V to supply the other dual USB. My stock cig/acc port had been changed a long time ago to constant 12V via the converter and I took opportunity to rewire it back to keyed 24V so my garmin GPS comes on and off with the truck, making it easier to track fuel mileage which is GPS verified.

It's a daily right now so constant on should not be an issue. If it turns out to be I can feed it keyed 24V on the upper display so there will be power to both only when running. Best solution is solar on the roof which is in future plans.

 

[thelal]

have mine to put in this week. Checked it works ; just need to do final wiring

 

[CruiserTrash]

Thread revival! Ok, so thanks to @george_tlc for paving the way on this. I installed a dual battery system and wanted to use the cheap Amazon dual voltmeter because I can stuff it inside a switch blank on the dash of my 60 for a more factory look.

I also ran into the problem where the dual voltmeter is always on since it’s directly connected to the second battery. I checked out the PC board and it’s different than the one dissected above - but the circuit was easy to break down. I’m leaving this write up below in case anyone else wants to this and ends up with a unit like mine.

In the main board each + input splits: they independently go to separate voltage sensing circuits (which have trimpots to adjust them!), and they also each pass through a diode and combine at a voltage regulator. The voltage regulator passes through a via to the backside of the board to a trace with a screen printed label that says “3.3V” next to it. This is the nominal B+ voltage to turn the displays on. All we have to do is get rid of the diode from the auxiliary battery to the 3.3V regulator and the display will only come on with the starter battery. In my application that + feed is switched with the ignition.

Here is the top side of the main board with the offending diode circled. Notice the diode above it - that’s for the topmost + input to power the 3.3V circuit. In my case the starter battery is connected to the + input labeled “VCC” and the house battery is on the + input labeled “OUT”. The word “OUT” is a strange way of labeling this - it’s not like it can be used as a pass through due to the diodes. Chinese manufacturing misnomer or typo I suspect.

Here’s the backside of the main board with the 3.3V trace labeled.

And here’s the top side again with the diode removed.

After that I used a meter to test actual voltage and then calibrated this thing as best as I could with the trimpots. It operates just as expected now. Thanks George!

FYI, I use a piece of dense foam with a slit in it so it slips around the PC board to hold it to the switch blank. Like this: