excess battery voltage

[gonad]

morning all
went to test brand new (six months unused)spare battery which is not connected to anything volt meter says 18VOLTS! tried other volt meter same reading any ideas somebody?

 

[sailorman]

a 24v battery ????

 

[Birdseye]

Yes. If its like most digital voltmeters, you havent noticed its reading mv not v and your battery is flat. The voltage out of a lead acid cell is limited by physical chemistry and cannot reach the 3 volts that your post suggests on its own..

Is the battery on charge? Please describe the situation in a bit more detail.

 

[gonad]

def 12V battery green lite showing fully charged just charged it about 3 weeks ago tested while not on charge thanks

 

[gonad]

volts not mv

 

[halcyon]

morning all
went to test brand new (six months unused)spare battery which is not connected to anything volt meter says 18VOLTS! tried other volt meter same reading any ideas somebody?

Are sure both positive and negative terminals are not connected to anything ?

Brian

 

[gonad]

positive! it is sitting on the floor in front of me

 

[DannyB]

Are you using a multi meter to check? You have it on DC volts don't you ? Not sure what you would get on AC, but it will be wrong.

 

[Birdseye]

When first charged the cells often show an over voltage that disappears over 24 hours. So sorry but I cant see any alternative to you reading the meters wrongly

 

[gonad]

def dc and an analogue meter reading the same

 

[gonad]

last charged 3 or 4 weeks ago

 

[DannyB]

Bit of thread drift, some (many) years ago, the company I worked for bought a bunch of new digital multimeters to replace the old analogue Avos. On a job one day I was picking up 110 volts on a circuit that should have been isolated, eventually, after finding I was getting 110 Volts on the earth, I went and dug out the AVO 8 and tested with it, nothing, zero, zip, nada. It would appear that some digital meters have such a high input impedance that they can display anything, like a radio antenna, they just pick up out of nothing, never really trusted multimeters after that.

 

[gonad]

thanks tested meter on other circuits showing 19! must be the meters?? strange both off kilter

 

[Birdseye]

def dc and an analogue meter reading the same

The electrochemical potential of a lead acid cell is 2.1 volts. You have 6 cells in a 12v battery. Leaving aside the short term issue of surface charge on the plates it is impossible for the cells to output 3 volts each. To the contrary, the electrochemical potential is so well fixed that they used to calibrate meters using standard cells ( I vaguely re!member it was silver cells).

Anyway, on the basis that yourbattery is disconnected and any surface charge has long dissipated, there is only one possibility allowed by the laws of physics. Your 18 reading is wrong.

 

[charles_reed]

I wonder when the 9v batteries in the meters were last renewed.
That or one needs new glasses.

 

[gonad]

yes must be the 9V batteries thanks

 

[neilf39]

Agree, I got some funny results with my multimeter until I replaced the internal battery. It must have been in there 5 years or more.

 

[VicMallows]

yes must be the 9V batteries thanks

"and an analogue meter reading the same"

What sort of analogue meter is this? No moving-coil (or even moving-iron) meter that I'm aware of requires a battery to measure voltage.

 

[SHUG]

You may have entered a parallell Universe where the physical laws are completely different to the normal world!!
Any other anomalies to report?

 

[Jamesuk]

Can we have video