Author Topic: Rechargeable 9V batterries for DMM or Alkaline only?  (Read 5344 times)

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Offline JenniferGTopic starter

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Rechargeable 9V batterries for DMM or Alkaline only?
« on: November 23, 2022, 08:05:15 am »
I was wondering if it's okay to use rechargeable 9V batteries in portable DMM's instead of Alkaline; i.e. to save money over time?  If not, how about the cheap Amazon branded 9V alkaline batteries?

https://www.amazon.com/EBL-Rechargeable-Batteries-Everyday-Detector/dp/B00H3ZXCNM

https://www.amazon.com/Amazon-Basics-Performance-All-Purpose-Batteries/dp/B0B4RSNDPG
Test Equip: GDM-8251a, UT61E, Probemaster, Tektronix 2225
Power Supplies: GPD-3303S (w/o overshoot problem)
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Offline Kleinstein

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #1 on: November 23, 2022, 08:26:56 am »
There are different types of rechargeble 9 V batteries. Some have 7 cells and some have 6 cells and thus a slightly lower voltage. It than also depends on the meter at which voltage they complain about insufficient voltage and show the battery symbol. It may happen that a meter will show low battery with a 6 cell block rather fast, as the nominal voltage of NiMH of some 1.2 to 1.24 V is about there where alkaline cells are considered empty. If the DMM is OK with some 7 V, than things are OK with a rechargible battery. Ideally this should be a low self discharge one, like the pre-charged ones, not an more old style high current one.  In most cases there is not that much money to be saved, as a DMM usually does not need that many batteries. It still depends on the meter and use. The rechargible cells also have a limited life time and may thus only get very few charge cycles. The other reason to use them is the lower chance of leakage.

It is hard to tell if the amazon or similar cheap 9 V blocks are OK. Some are and some are poor. Expensive alkaline cells can also leak. If leakage is the main issue, long life Lithium primary cells may be an option too.  I would have a slight problem with buying 12 batteries, as this would last for quite a long time and the shelf life is limited.
 

Offline tooki

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #2 on: November 23, 2022, 09:41:31 am »
I wouldn’t do it in a meter not expressly designed for them (for example, some of the Keysight models, which charge the battery via the input jacks). On the one hand, you’ll get low battery indications more often, but also, most meters’ battery compartments aren’t designed to be opened that frequently.
 

Offline HighVoltage

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #3 on: November 23, 2022, 10:06:37 am »
It depends on the DMM

I am using some 9V 600mAh EBL (6F22) on some DMM and current clamps with really good success on those devices that have low battery indicator below 8.0 V. The EBL have around 8.4V idle voltage when fully charged.

Any DMM that shows a low battery indicator at a higher voltage, I am still using Alkaline.
 

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Offline J-R

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #4 on: November 23, 2022, 10:12:15 am »
Since we know from your other thread that you are most likely doing data logging, the best off-the-shelf solution seems like a Lithium-Ion rechargeable 9V @ about 600mAh:
https://www.eblofficial.com/products/9v-rechargeable-batteries
Note: check into the low-voltage behavior of the DMM.  If it is going to freak out at say 8.5V, then these are probably not going to work.

There is also the 1200mAh Ultralife 9V Lithium (primary, non-rechargeable), but they are going to be expensive if you're really burning through them.  Retail price is between $10-$15 each, but I've had good luck on ebay buying the 10 packs for just under $50.
Note: these are every so slightly larger than a standard 9V (still within spec, according to them, though).  So in some rare cases they may not fit.

Some will cry foul, but you could also try an external supply or battery pack depending on the use case.
 

Offline JenniferGTopic starter

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #5 on: November 23, 2022, 10:45:31 am »
Since we know from your other thread that you are most likely doing data logging, the best off-the-shelf solution seems like a Lithium-Ion rechargeable 9V @ about 600mAh:
https://www.eblofficial.com/products/9v-rechargeable-batteries
Note: check into the low-voltage behavior of the DMM.  If it is going to freak out at say 8.5V, then these are probably not going to work.

There is also the 1200mAh Ultralife 9V Lithium (primary, non-rechargeable), but they are going to be expensive if you're really burning through them.  Retail price is between $10-$15 each, but I've had good luck on ebay buying the 10 packs for just under $50.  I could probably get like $150 or so for this 8251A to go towards purchase of a better bench DMM.
Note: these are every so slightly larger than a standard 9V (still within spec, according to them, though).  So in some rare cases they may not fit.

Some will cry foul, but you could also try an external supply or battery pack depending on the use case.

Yeah I'm doing data logging with UT61E.  Perhaps I should get a better bench DMM? I'm currently sing the 8251A and I don't think you can data log with it, even though it has a serial port and usb.   Are there any good bang for the buck bench DMM with data logging?  Fairly accurate etc?  This 8251A is 120K count.
Test Equip: GDM-8251a, UT61E, Probemaster, Tektronix 2225
Power Supplies: GPD-3303S (w/o overshoot problem)
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Offline Kleinstein

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #6 on: November 23, 2022, 11:00:11 am »
An external supply is dangerous with most DMMs: there is usually no isolation from the measurement part to the batteries.

A first step would be to just measure the voltage at which the DMM starts to show low battery. This could be an old alkaline battery removed from the DMM.

The moden NiMH batteries are not that much lower capacity than alkaline. So for the screws to the battery compartment it does not make so much difference.

 
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Offline slugrustle

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #7 on: November 23, 2022, 06:11:56 pm »
The Powerex MHR9VP is a low self-discharge "9V" NiMH battery that lists as 9.6V nominal with 230mAh capacity: https://mahaenergy.com/powerex-precharged-9-6v-230mah-1-pack/.

I just bought some with the associated MH-C490F charger (https://mahaenergy.com/mh-c490f-9v-charger/) expressly for use in DMMs, thermocouple readers, and similar equipment but haven't used them yet.  I'm waiting until the alkaline 9Vs that they're intended to replace wear out.
 

Offline J-R

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #8 on: November 23, 2022, 08:23:15 pm »
It's not hard to provide a floating/isolated supply to the DMM.

At DMM loads, 9V Ni-MH (230mAh) is less than half the capacity of Alkaline (550mAh).
 

Offline mariush

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #9 on: November 23, 2022, 08:50:59 pm »
A multimeter consumes a few mA of current, so you could easily have a super tiny voltage doubler circuit on a lithium battery produce around 6-7.5v from 3.7v .. 4.2v

For example LM2765 -  https://www.ti.com/lit/ds/symlink/lm2765.pdf - or MAX1683 (more expensive but no diode required) - https://datasheets.maximintegrated.com/en/ds/MAX1682-MAX1683.pdf

The 9v battery is 48.5mm x 26.5mm x 17.5mm ... so you can easily find a lithium battery, here's just one example : https://www.digikey.com/en/products/detail/tinycircuits/ASR00035/9808767

 

Offline Kleinstein

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #10 on: November 23, 2022, 08:56:44 pm »
It's not hard to provide a floating/isolated supply to the DMM.

Yes : the obvious solution is using a battery of some kind  >:D

Getting a very well isolated DCDC converter to provide mains power is however tricky.  The usual CAT 2 and even more CAT 3 safety rating call for withstanding quite high transient voltages. A 2nd problem is that the usual DCDC converters tend to inject quite some high frequency common mode signal that can cause EMI problems. There are circuits  / custom designs for relatively good isolated DCDC converters, but this really hard stuff if it needs to fit inside the small battery compartment and the isolation is still inferior to a simple battery.

There is no need to build a voltage doubler for a Li.ion cell. There are ready made 2S li-ion batteries with protection in the 9 V block form factor. This gives a higher capacity rechargible option.
 

Online bdunham7

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #11 on: November 23, 2022, 09:41:51 pm »
Yeah I'm doing data logging with UT61E.  Perhaps I should get a better bench DMM? I'm currently sing the 8251A and I don't think you can data log with it, even though it has a serial port and usb.   Are there any good bang for the buck bench DMM with data logging?  Fairly accurate etc?  This 8251A is 120K count.

I don't have the UT61E, but as long as its battery cutoff is <7.2V, the EBL two-cell Li-ion 9 volt batteries should be great.  Most reasonably designed devices will have the cutoff below that 7.2V mark because that is 1.2V/cell and less than that with alkaline batteries is wasting a lot of their energy.  According to this video, your UT61E will have a cutoff below 7.0V.



As far as a bench meter for logging, check this thread on user HKJ's Test Controller program.

https://www.eevblog.com/forum/testgear/program-that-can-log-from-many-multimeters/

Your GDM-8251 should support logging if you find the software to do so.  GW's webpage has USB and LabView drivers for it, but I don't see the DMM-Viewer program for logging.  I had a GDM-8251 for a bit but I don't recall setting it up for logging.  I'm sure there's a way.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline mariush

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #12 on: November 23, 2022, 10:21:58 pm »
Strictly in the case of UT61E ( which I own), I think the meter shows low battery voltage at around 5.4v and will still go and measure well down to around 3v.

But the serial output may stop working right before you hit 3v due to the optical isolation (forward voltage of led used)

I actually made a battery replacement thing using a 20F -ish (don't remember exact value) 2.5v supercapacitor and a LT1307 step-up regulator to 5.6v ... charge the capacitor at 2.4v for 1 minute, and then it would last for around 40 minutes or something like that.

You can check in the part 3 of this review at around 20 minutes in :




You could probably use a digital isolator IC like Adum5000 if you want to power the meter from an external supply, for example : https://www.analog.com/media/en/technical-documentation/data-sheets/adum5000.pdf
Such isolators are expensive and noisy and low efficiency, like 33% efficiency - but if powered from some wallwart i guess you wouldn't care that you waste 10mA or so to get isolated 2-3mA to the meter
 
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Offline AVGresponding

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #13 on: November 24, 2022, 06:32:45 am »
I use Znter Li-ion, they give a steady 9.0-9.1V across the entire discharge until shutoff, as they have an internal boost regulator. The only downside is that you don't get a low battery warning from your DMM...
A Fluke 87V lasts at least 6 months on a charge.
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Offline james_s

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #14 on: November 24, 2022, 07:31:31 am »
I've used rechargeable 9V NiMH batteries in my Fluke 87 since new, it works fine. I can't see any reason why it wouldn't be fine in any other meter. With very few exceptions I don't buy disposable batteries anymore and haven't in years.
 

Offline JenniferGTopic starter

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #15 on: November 24, 2022, 07:53:56 am »
Thanks for all the replies.  Looks like the UT61EA can handle the rechargeables fine. I'll get the 7 cell instead of 6 cell.

With all the data logging I am doing I think the rechargeable perhaps makes sense.  The 9V battery 2 days ago read 9.7V and now it is at 9.2V.   But I've been running a lot of data logging tests since I wrote my own C++ class to read from it on my Arduino Mini Mega.
Test Equip: GDM-8251a, UT61E, Probemaster, Tektronix 2225
Power Supplies: GPD-3303S (w/o overshoot problem)
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Offline james_s

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #16 on: November 24, 2022, 08:15:30 am »
Rechargeable batteries make sense for almost everything. They're not expensive anymore, they don't rapidly self discharge anymore, and they are much less likely to leak.
 

Offline iMo

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #17 on: November 24, 2022, 08:15:42 am »
I've been using rechargeable 9V battery (NiMH) in my Metex handheld. Mounted a 2.5mm jack socket near the battery bay, and wired a diode and a resistor for external charging. While meter on the desk the battery is trickle charged..
Readers discretion is advised..
 

Offline james_s

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #18 on: November 24, 2022, 08:17:14 am »
I've been using rechargeable 9V battery (NiMH) in my Metex handheld. Mounted a 2.5mm jack socket near the battery bay, and wired a diode and a resistor for external charging. While meter on the desk the battery is trickle charged..

Generally speaking I'd say this is a bad idea, it compromises the safety of the meter and invalidates any CAT rating that it has. The battery compartment is part of the safety isolation of most meters.
 
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Offline iMo

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #19 on: November 24, 2022, 08:20:38 am »
I've been using rechargeable 9V battery (NiMH) in my Metex handheld. Mounted a 2.5mm jack socket near the battery bay, and wired a diode and a resistor for external charging. While meter on the desk the battery is trickle charged..

Generally speaking I'd say this is a bad idea, it compromises the safety of the meter and invalidates any CAT rating that it has. The battery compartment is part of the safety isolation of most meters.

"While meter on the desk and not in use the battery is trickle charged.."
And you may create an isolation cover (3D print) for the small 2.5mm socket..

PS: is there a handheld dmm with wireless inductive charger available??
« Last Edit: November 24, 2022, 08:31:08 am by imo »
Readers discretion is advised..
 

Online tszaboo

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #20 on: November 24, 2022, 08:43:09 am »
I use USB rechargeable battery, that has a DC-DC converter inside. Works great. Why? Because I don't have a nice 9V charger or battery, they don't make LSD 9V. Or they don't advertise it well.
 

Offline JenniferGTopic starter

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #21 on: November 24, 2022, 09:30:34 am »
I use USB rechargeable battery, that has a DC-DC converter inside. Works great. Why? Because I don't have a nice 9V charger or battery, they don't make LSD 9V. Or they don't advertise it well.

Do you have a link to the one you bought? I'll probably buy that one.   Sounds good.
Test Equip: GDM-8251a, UT61E, Probemaster, Tektronix 2225
Power Supplies: GPD-3303S (w/o overshoot problem)
Soldering Station:  Hakko 926
 

Offline coppercone2

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #22 on: November 24, 2022, 09:45:40 am »
tenergy 9v NiMH
 

Offline DavidKo

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #23 on: November 24, 2022, 09:53:40 am »
Look for the one closest to you - try google.

In the school lab, the rechargeables were used in all DMM (20 years ago). No issues at all. The reason was that always someone left them turned on.

I use accus in the devices where I do not want a leak and have low power consumption and are not for daily use - termometer, door ring, DMM etc. Alternatively I use long live batteries - for example in the clock, where everyone notices.

I have bad experience with accus in case that they are used in power toys in amount 3 and more. The same capacity is than important, but even so the children have tendency to discharge them deep and the worst NiMH have tendency to charge negative and get destroyed. This can happen in every device, but it is hard to explain this to children (and wife ;D).
 

Online tszaboo

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Re: Rechargeable 9V batterries for DMM or Alkaline only?
« Reply #24 on: November 24, 2022, 11:07:00 am »
I use USB rechargeable battery, that has a DC-DC converter inside. Works great. Why? Because I don't have a nice 9V charger or battery, they don't make LSD 9V. Or they don't advertise it well.

Do you have a link to the one you bought? I'll probably buy that one.   Sounds good.
It's from years ago from Aliexpress. I don't know if the company making it is still around, or if it's rebranded.
Others wrote brand, they are probably the same inside.
 


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