Battery box with voltmeter does not work

[Buehgemeiste]

I built a box for two sla batteries to take it to the outside and power an active speaker.
I included two voltmeters and a pushbutton switch that enables the voltmeters, a 10A fuse und a dc-jack.
Everything works as long as nothing is connected to the output jack of the box.
Everything works means that i measure the anticpated voltage at the dc-jack (~25V), the button enables the voltmeters, the voltmeters show the anticipated voltages (~12.5V)...
But then...
As soon as a connector is plugged into the jack the voltage drops to about 11V, the adressed amplifier doesn't power up, one voltmeter shows nothing.
What is this about?
There is no switch built into the dc-jack.
I tried different cables.
It makes no difference if a load is connected or the cable is open.
I guess there is something about the voltmeters that i do not understand.
I use that kind of voltmeters:
https://de.aliexpress.com/item/1pc-...lgo_pvid=128d2f4e-08dc-425b-99b9-976531078e5e
Maybe some diodes are required?

I misused ltspice to draw the circuit .
vm1 and vm2 represent the voltmeters.
Their VCC wires go to the switch which connects them to the highest potential in the circuit.

Thanks in advance!

 

[KatieandDad]

I've never encountered a voltmeter with three terminals ??

What do the amplifiers require ? +/- 12V or + 24V ?

 

[scottjoplin]

Does the voltmeter have it's own battery or is it powered from the circuit? If it's the latter, I'm pretty sure that's not going to work, it needs to be isolated from the voltages it's measuring

 

[Buehgemeiste]

I've never encountered a voltmeter with three terminals ??

What do the amplifiers require ? +/- 12V or + 24V ?

They need +24V (up to 36v is ok).

Does the voltmeter have it's own battery or is it powered from the circuit? If it's the latter, I'm pretty sure that's not going to work, it needs to be isolated from the voltages it's measuring

They are powered from the same supply.

 

[DF96]

Draw the whole circuit, not just a vague diagram. You will then see how you are shorting out one of the batteries.

 

[scottjoplin]

How did I miss that! Damn Haha

 

[Buehgemeiste]

i found my mistake:
the dc jack actually has a switch.
i mistook the pins.
now everything works and there is no short.
the voltmeters work as intended.

 

[KatieandDad]

Well done, sometimes our questions incite the thoughts that cure the faults.

 

[Buehgemeiste]

Excuse the false alert.

 

[scottjoplin]

Ha ha, don't worry about it, happens a lot. Decent of you to say