Using Rechargeable Batteries On Multimeters

[Kahraba]

Hey fellas,

I just bought a new digital multimeter, It requires two AAA batteries and they were not included.

I have two AAA 900mAh rechargeable batteries, i installed them to check the multimiter, i noticed on each setting the numbers are fluctuating.

I read the manual to see if this is normal, i read that i should not use rechargeable and lithium batteries on this unit.

- Why can't i use rechargeable batteries on multimiteres?

- Is it the reason for the numbers to fluctuate? if not, should it be reading 0 always?

 

[steptoe]

Normal batteries are 1.5v

Rechargeable are 1.2v

 

[Kahraba]

Normal batteries are 1.5v

Rechargeable are 1.2v

Thanks for the quick response!

OK just to know about the numbers fluctuating, is it due to the batteries or a fault or it's normal?

of course i meant this when it's not connected to anything.

 

[Sidewinder]

On which range, and what is the status of the leads when you observe this fluctuation?

 

[Andy™]

fluctuating readings are often caused by low batteries. as already pointed out, rechargeable batteries have a lower voltage, which might not be enough for it to work correctly

 

[Bruspark]

To be a touch more specific

An alkaline Cell is 1.5V when new and under no load, 1.2Vand falling under a moderate load falling steadily to 0.9V when dead

NiMh rechargeables are 1.3v when fully charged and under no load, drop to 1.2v under load but holding up well before finally diving to 0.9 when dead

The maximum current delivery is higher from NiMH than Alkaline as the internal resistance is lower.  This MAY upset some electronic devices (e.g. oscillation)

Rechargeable self discharge is dependent on their particular formula but they usually get flat in about a year.

For equipment with a cut off point of 0.9V per cell there is no reason a Rechargeable wouldn't work where an alkaline does

The manufacturer may ban it because the fire risk of an internal short in the device is greater

A alkaline calibrated battery meter is likely to give very late /little warning of a NiMH running out . .

For occasionally used test gear the Battery may be dead every time you need to use it

HTH

 

[Richard-the-Ninth]

Thanks for the quick response!

OK just to know about the numbers fluctuating, is it due to the batteries or a fault or it's normal?

of course i meant this when it's not connected to anything.

Would it have not been quicker to try some and find out for yourself.

 

[Kahraba]

On which range, and what is the status of the leads when you observe this fluctuation?

On DC and AC (Auto), Leads were not connected to anything.

fluctuating readings are often caused by low batteries. as already pointed out, rechargeable batteries have a lower voltage, which might not be enough for it to work correctly

Yeah i never knew rechargeables are 1.2 V until now on this forum.

To be a touch more specific

An alkaline Cell is 1.5V when new and under no load, 1.2Vand falling under a moderate load falling steadily to 0.9V when dead

NiMh rechargeables are 1.3v when fully charged and under no load, drop to 1.2v under load but holding up well before finally diving to 0.9 when dead

The maximum current delivery is higher from NiMH than Alkaline as the internal resistance is lower.  This MAY upset some electronic devices (e.g. oscillation)

Rechargeable self discharge is dependent on their particular formula but they usually get flat in about a year.

For equipment with a cut off point of 0.9V per cell there is no reason a Rechargeable wouldn't work where an alkaline does

The manufacturer may ban it because the fire risk of an internal short in the device is greater

A alkaline calibrated battery meter is likely to give very late /little warning of a NiMH running out . .

For occasionally used test gear the Battery may be dead every time you need to use it

HTH

Great Info, thanks for that!

Would it have not been quicker to try some and find out for yourself.

I didn't have alkaline batteries around at the time.

 

[Sidewinder]

On DC and AC (Auto), Leads were not connected to anything...

Almost certainly just coupled noise due to em interference in the environment coupled to the inputs by the leads, thus causing phantom readings as the input impedance is so high.

Short the lead tips together and see if you get 0 V.