Rechargeable 9V batterries for DMM or Alkaline only? - Page 1
Forum section: electronics / testgear

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 23, 2022, 08:05:15 am
content: 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/B00H3ZXCNMhttps://www.amazon.com/Amazon-Basics-Performance-All-Purpose-Batteries/dp/B0B4RSNDPG

author: Kleinstein
author_rank: Super Contributor
timestamp: November 23, 2022, 08:26:56 am
content: 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.

author: tooki
author_rank: Super Contributor
timestamp: November 23, 2022, 09:41:31 am
content: 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.

author: HighVoltage
author_rank: Super Contributor
timestamp: November 23, 2022, 10:06:37 am
content: It depends on the DMMI 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.

author: J-R
author_rank: Super Contributor
timestamp: November 23, 2022, 10:12:15 am
content: 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-batteriesNote: 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.

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 23, 2022, 10:45:31 am
content: Quote from: J-R on November 23, 2022, 10:12:15 amYeah 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.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 23, 2022, 11:00:11 am
content: 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.

author: slugrustle
author_rank: Frequent Contributor
timestamp: November 23, 2022, 06:11:56 pm
content: 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.

author: J-R
author_rank: Super Contributor
timestamp: November 23, 2022, 08:23:15 pm
content: 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).

author: mariush
author_rank: Super Contributor
timestamp: November 23, 2022, 08:50:59 pm
content: 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 .. 4.2vFor 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.pdfThe 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

author: Kleinstein
author_rank: Super Contributor
timestamp: November 23, 2022, 08:56:44 pm
content: Quote from: J-R on November 23, 2022, 08:23:15 pmYes : the obvious solution is using a battery of some kindGetting 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.

author: bdunham7
author_rank: Super Contributor
timestamp: November 23, 2022, 09:41:51 pm
content: Quote from: JenniferG on November 23, 2022, 10:45:31 amI 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 userHKJ'sTest 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.

author: mariush
author_rank: Super Contributor
timestamp: November 23, 2022, 10:21:58 pm
content: 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.pdfSuch 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

author: AVGresponding
author_rank: Super Contributor
timestamp: November 24, 2022, 06:32:45 am
content: 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.

author: james_s
author_rank: Super Contributor
timestamp: November 24, 2022, 07:31:31 am
content: 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.

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 24, 2022, 07:53:56 am
content: 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.

author: james_s
author_rank: Super Contributor
timestamp: November 24, 2022, 08:15:30 am
content: 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.

author: iMo
author_rank: Super Contributor
timestamp: November 24, 2022, 08:15:42 am
content: 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..

author: james_s
author_rank: Super Contributor
timestamp: November 24, 2022, 08:17:14 am
content: Quote from: imo on November 24, 2022, 08:15:42 amGenerally 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.

author: iMo
author_rank: Super Contributor
timestamp: November 24, 2022, 08:20:38 am
content: Quote from: james_s on November 24, 2022, 08:17:14 am"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??

author: tszaboo
author_rank: Super Contributor
timestamp: November 24, 2022, 08:43:09 am
content: 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.

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 24, 2022, 09:30:34 am
content: Quote from: tszaboo on November 24, 2022, 08:43:09 amDo you have a link to the one you bought? I'll probably buy that one. Sounds good.

author: coppercone2
author_rank: Super Contributor
timestamp: November 24, 2022, 09:45:40 am
content: tenergy 9v NiMH

author: DavidKo
author_rank: Frequent Contributor
timestamp: November 24, 2022, 09:53:40 am
content: 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).

author: tszaboo
author_rank: Super Contributor
timestamp: November 24, 2022, 11:07:00 am
content: Quote from: JenniferG on November 24, 2022, 09:30:34 amIt'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.

author: bdunham7
author_rank: Super Contributor
timestamp: November 24, 2022, 03:34:36 pm
content: I highly recommend:https://www.amazon.com/EBL-Rechargeable-Batteries-Battery-Lithium-ion/dp/B08HRXHKQV

author: AVGresponding
author_rank: Super Contributor
timestamp: November 24, 2022, 04:48:46 pm
content: Quote from: JenniferG on November 24, 2022, 09:30:34 amAliexpressHobbyKingPersonally I'd trust HobbyKing more than Aliexpress. YMMV. HobbyKing is also where I buy my AA and AAA LSD Ni-MH, and AA Ni-Zn.

author: james_s
author_rank: Super Contributor
timestamp: November 24, 2022, 06:56:06 pm
content: Quote from: tszaboo on November 24, 2022, 08:43:09 amSure they do, I have a pile of them, maybe they don't advertise it well, but typically the package will say something like "pre-charged" or "ready to use". Most NiMH batteries currently made are LSD, it isn't a special thing you have to search for anymore.

author: BillyO
author_rank: Super Contributor
timestamp: November 24, 2022, 07:43:55 pm
content: I've used a 6 cell D-cell battery holder for cheap isolated powering of 9V equipment for long periods. You can get them on eBay or Amazon for about $5.There are 4 advantages to doing this.1) Alkaline D-cells are relatively cheap.2) They can be used for lot's of other household things, like flashlights, toys, etc. So won't go to waste before they are depleted.3) Being external, if they leak they will not destroy your meter.4) They pack a lot of energy. They will likely power a UT61E for many, many months.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 24, 2022, 08:30:15 pm
content: D-cells are very much running out of favor in many cases. If not careful you may end up with an AA size cell with extra spacer to make it fit the old form factor. An alkaline AA tends to last not as long as a class D dry cell though. Not many new toys / tools use the D-size - it is more like going obsolete: low power devices usually don't need that much capacity and higher power devices tend to use rechargibles.Even with just an external battery, this makes it tricky to keep the isolation barrier with an extra cable / connector.

author: David Hess
author_rank: Super Contributor
timestamp: November 25, 2022, 04:34:01 pm
content: I just use alkaline 9 volt batteries. They last for years so rechargeable batteries do not make a lot of sense.Quote from: mariush on November 23, 2022, 08:50:59 pmEarly Texas Instruments calculators had 1 or 2 AA NiCd battery packs with a small boost converter to produce 9 volts.

author: BillyO
author_rank: Super Contributor
timestamp: November 25, 2022, 07:45:28 pm
content: Quote from: Kleinstein on November 24, 2022, 08:30:15 pmI try to buy things that only use rechargeable, D or C cells as much as possible. I just hate spending the price of a D cell on a AAA and those 9V batteries are outrageous for the amount of energy in them. TV remotes suck.I guess if the OP is logging data in a CAT IV OR CAT III environment, then isolation might be a thing. Otherwise I'm not sure having a couple of thin wires coming out the back of the meter represents a huge risk.

author: james_s
author_rank: Super Contributor
timestamp: November 25, 2022, 07:58:09 pm
content: 9V batteries are my favorite small alkaline, they rarely leak because they have a double casing. NiMH has been good enough for around 15 years though that I generally consider alkaline batteries obsolete.

author: BeBuLamar
author_rank: Super Contributor
timestamp: November 26, 2022, 12:48:33 pm
content: Unless the 9V alkaline leaks I would use it for a DMM. The 9V battery in my Fluke 87V lasts a long time. Rechargeable is very likely to be dead whenever you need to use it.

author: daisizhou
author_rank: Super Contributor
timestamp: November 26, 2022, 01:02:02 pm
content: You can try this DIY solutionhttps://www.mydigit.cn/thread-163962-1-1.html

author: wasedadoc
author_rank: Super Contributor
timestamp: November 26, 2022, 01:31:16 pm
content: Quote from: daisizhou on November 26, 2022, 01:02:02 pmSolution to what?And that is the first time in more than 60 years that I have seen the output from a power supply come out of the base of a transistor.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 26, 2022, 03:06:26 pm
content: Quote from: BeBuLamar on November 26, 2022, 12:48:33 pmMaybe with old technology rechargeables, but modern ones whether Ni-MH LSD, or Li-ion, are much better. As I already said, my F87V lasts at least 6 months on a charge with a Znter 600mAh Li-ion.

author: james_s
author_rank: Super Contributor
timestamp: November 26, 2022, 07:30:00 pm
content: Quote from: BeBuLamar on November 26, 2022, 12:48:33 pmWhy would it be dead? As I said earlier. I've been using rechargeable 9V batteries in my Fluke 87 for years, they work fine, the modern ones are all LSD, you can leave it in the drawer for a year and pull it out and the battery won't be dead.

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 26, 2022, 10:18:37 pm
content: Quote from: james_s on November 26, 2022, 07:30:00 pmWhich rechargeable 9V do you use?

author: james_s
author_rank: Super Contributor
timestamp: November 26, 2022, 11:57:57 pm
content: Quote from: JenniferG on November 26, 2022, 10:18:37 pmI have several different types, EBL, Bakth, Tenergy, Thunderbolt (Harbor Freight), and some others, all NiMH. They all seem to be pretty similar.

author: daisizhou
author_rank: Super Contributor
timestamp: November 27, 2022, 01:40:30 am
content: There may be some mistakes in the schematic diagram, but the point is that it has no switch, and it is 3.6V-4.2V boosted to 9V, which can be used instead of a 9v battery

author: BradC
author_rank: Super Contributor
timestamp: November 27, 2022, 02:03:20 am
content: I moved from NiMH to these about 4 years ago :https://www.batteriesdirect.com.au/shop/product/24926/lp702235-bp1.htmlI use them in everything now. Meters, Shure wireless beltpack, toys...I spent years fighting with NiMH and the Powerex LSD 9.6V were the best, but not a patch on these lithium units for lifetime and reliability. They are a "nominal 8.4V", and all my devices work and give me sufficient low battery warning to swap them before they cut off.

author: mwb1100
author_rank: Frequent Contributor
timestamp: November 27, 2022, 04:51:50 am
content: Quote from: bdunham7 on November 24, 2022, 03:34:36 pmAny experience with these?:-https://www.amazon.com/EBL-USB-Rechargeable-Lithium-Batteries/dp/B086GTFGPP(the 5400mWh rating on them ciphers out to the same 600mAh as you linked to). If they work as well, I'd rather not have to make room for yet another charger - especially one that only handles 9V batteries.