ANENG A3009 pen multimeter drains the battery - Page 1
Forum section: electronics / testgear

author: vladc77
author_rank: Regular Contributor
timestamp: February 08, 2025, 09:46:04 pm
content: My ANENG A3009 multimeter drains the battery even when it's switched off. If I leave the battery in, it's always dead when I go to use it again. Has anyone else experienced this issue with the A3009? Is there a known fix for this?

author: puxe
author_rank: Contributor
timestamp: February 09, 2025, 08:39:19 am
content: I have a A3008 and put a rechargeable AAA battery in it about 6+ weeks ago and it is fine .... I just checked a 1.5V AA battery and all good.

author: csuhi17
author_rank: Frequent Contributor
timestamp: February 09, 2025, 01:35:11 pm
content: Quote from: vladc77 on February 08, 2025, 09:46:04 pmWhat kind of battery do you use?How much does it consume when it is off?How much when it is on?I use a rechargeable 1.5V lithium battery (the one that needs to be charged via a USB port), and it hasn't run down in over a year.I couldn't measure its idle consumption, it's less than 0.1mA.When it is on, the device can draw up to 500mA until it normalizes, then it drops back to a constant 25mA.The lowest voltage where it still turns on is 0.6V and a little instabil and it draws more current when it is on around 75mA.

author: Fungus
author_rank: Super Contributor
timestamp: February 09, 2025, 02:46:22 pm
content: If you have another meter then measure the current drain when it's off.If you don't have another multimeter then you just found out why everybody on EEVBLOG says "youneedmore than one multimeter!"(preferably several more)

author: vladc77
author_rank: Regular Contributor
timestamp: February 09, 2025, 08:34:10 pm
content: I'm using an Energizer Industrial battery, which I believe should be suitable.I've noticed something strange with my ANENG A3009 multimeter. If I let it shut off automatically (it powers down after 5 minutes of inactivity), the battery seems fine. I left it yesterday in this auto-shutdown mode and checked the battery today; it still had power. However, if I manually turn it off by holding the select button for more than two seconds, the battery drains. Is it possible there's another way to manually power it off that doesn't cause this drain?

author: csuhi17
author_rank: Frequent Contributor
timestamp: February 09, 2025, 08:51:35 pm
content: Quote from: vladc77 on February 09, 2025, 08:34:10 pmso the regular 1.5V AAA battery. OK.The third solution is to remove the battery, then it will definitely turn off.But the question is, can youmeasurethe current consumption?

author: vladc77
author_rank: Regular Contributor
timestamp: February 09, 2025, 08:53:38 pm
content: I'm going to get another multimeter and measure the current draw of the ANENG A3009 to see what's happening.

author: Fungus
author_rank: Super Contributor
timestamp: February 09, 2025, 08:54:34 pm
content: Quote from: vladc77 on February 09, 2025, 08:34:10 pmIt's actuallypossiblethat it's faulty, and there's nothing you can do except remove the battery.

author: Paul T
author_rank: Regular Contributor
timestamp: February 11, 2025, 03:14:09 am
content: You may want to take a good look at the ANENG's terminal design and how it interacts with the cell. The can of an alkaline battery is (+) and ends at the (-) end of the cell. Plus, the wrapper of the Energizer has a semi-conductive layer exposed at the cut ends and the side seam. If the terminals can press on the negative electrode and the exposed wrapper metal at the same time, you may have a leak (short circuit of unknown resistance).I can sit here with my multimeter in megohms and repeatedly measure a resistance at the seam of my Energizers with the leads spaced about 1 mm apart.As a remedy, try a rechargeable cell or a lithium primary, which have a (-) can which ends with a raised nipple at the (+) end. Insulating material could work too, such as a Mylar washer. Or try cells that have a non-shiny wrapper.The metallic wrapper Energizers also cause problems with a series of cells which point opposite directions beside each other (zig zag), regardless alkaline or lithium. A strap that runs down the side of the cell can be of particular concern.I think many people assume the cathode of all cells is the can, even device manufacturers. This can cause problems with sheet metal formed, flat coils, soldered wires, or helical springs that are not on-center with narrow ended cells like AAA or AA. There is much more that can go wrong than most people realize.

author: vladc77
author_rank: Regular Contributor
timestamp: February 11, 2025, 04:47:40 am
content: Thanks for all the ideas and suggestions! I'll give that a try too, after my trip!

author: vladc77
author_rank: Regular Contributor
timestamp: February 15, 2025, 04:38:42 am
content: I've finally been able to measure the current draw. Here are the results:Turned on: 62 mATurned off: 36 mAThese values seem quite high, especially the 0.36 mA when the multimeter is off. I'm not sure what's causing such a high drain. I removed the battery from the battery compartment and connected it externally with wires, but the drain persists.

author: Fungus
author_rank: Super Contributor
timestamp: February 15, 2025, 05:57:37 pm
content: Quote from: vladc77 on February 15, 2025, 04:38:42 amThere's your answer!

author: qbpm
author_rank: Newbie
timestamp: February 15, 2025, 07:26:17 pm
content: I had a similar issue in A3007. It drain 4.94mA when turned off. The cause was a 100uF SMD capacitor. I replaced it and it is ok.

author: vladc77
author_rank: Regular Contributor
timestamp: February 15, 2025, 11:46:27 pm
content: Thanks, qbpm! That's incredibly helpful. I'll replace it and hopefully that solves the problem. What's the voltage rating for this CMD capacitor?

author: Fungus
author_rank: Super Contributor
timestamp: February 16, 2025, 02:11:55 am
content: Try just removing it and see if it fixes the drain.

author: vladc77
author_rank: Regular Contributor
timestamp: February 16, 2025, 02:46:15 am
content: Things are looking much better without the 100µF SMD capacitor!Turned on: 20 mATurned off: 0.014 mAI don't have any 100µF SMD capacitors on hand. I'm wondering if the voltage rating is critical in this particular application.

author: qbpm
author_rank: Newbie
timestamp: February 16, 2025, 09:59:15 am
content: If I remember correctly, there was 3.3 volts on this capacitor. You can measure with another voltmeter. Just select the voltage with some margin. I didn't have 100 uF and the one I soldered in was 47uF and in my case it is ok.

author: Fungus
author_rank: Super Contributor
timestamp: February 16, 2025, 10:27:22 am
content: Quote from: vladc77 on February 16, 2025, 02:46:15 amIt's easy to measure the voltage across that SMD pad where the capacitor was... it's unlikely to be above the battery voltage though (unless there's a boost converter in there)Measure it, multiply it by three or four for safety margin... there's your voltage.

author: vladc77
author_rank: Regular Contributor
timestamp: February 16, 2025, 09:40:35 pm
content: Thanks everyone for your help! I'll replace the SMD capacitor as soon as it arrives, and I'm hoping that will be a permanent fix.

author: Paul T
author_rank: Regular Contributor
timestamp: February 17, 2025, 04:18:44 am
content: Usually ceramic capacitors are very low leakage. Perhaps they are not being used properly in the circuit. Those bright orange Vishay tantalums are a nice item. Just be aware they are polarized.

author: Kean
author_rank: Unknown
timestamp: February 17, 2025, 04:43:53 am
content: An MLCC may have very low leakage under normal conditions, but they are subject to cracking that can lead to high leakage or shorts. I've seen this especially with higher capacitance values, thus more layers and/or larger package sizes.When placed near the edge of the PCB in particular, the part can be subjected to forces that can cause cracks during manufacturing and assembly, possibly even during shipping or normal usage. Soft termination on MLCCs has become popular to help reduce these stresses.Leakage currents could also be due to process or environmental issues (cleanliness/humidity).In this case, and based on the placement of the capacitor and narrow PCB, I suspect that it could be damaged by rough handling as the common input jack is attached nearby.

author: Fungus
author_rank: Super Contributor
timestamp: February 17, 2025, 05:56:58 am
content: Quote from: Kean on February 17, 2025, 04:43:53 amGet one with legs and bodge it in.

author: Kean
author_rank: Unknown
timestamp: February 17, 2025, 06:10:56 am
content: Quote from: Fungus on February 17, 2025, 05:56:58 amThey do indeed make MLCCs with legs, but they are way more expensive than normal ones. I'm sure they are justified in some applications.Some look like centipedes! The images below (from Digikey) are possibly a bit too big for this application.

author: Fungus
author_rank: Super Contributor
timestamp: February 17, 2025, 07:15:11 am
content: I meant one of those lentil-shaped ones.

author: Kean
author_rank: Unknown
timestamp: February 17, 2025, 08:25:30 am
content: Quote from: Fungus on February 17, 2025, 07:15:11 amI assume you don't mean a ceramic disc as they are not available in the required capacitance.So a monolithic capacitor? OK, yes but those are just SMD MLCCs with through hole leads and encapsulated in epoxy.Looking at Digikey, they only have one of those in stock at 100uF and it is only rated for 6.3V (FK22X5R0J107MN), whereas they have over one hundred SMD 100uF parts from 6.3V to 25V and 0805 size up.All of the SMD parts are cheaper, and many are significantly (5x) cheaper than the monolithic through hole option. They have higher voltage parts too, but those are not relevant.I doubt too many people have high value (47uF and above) mono caps sitting around, but it does look like there would be space if done neatly.I opened up one of my A3008s and despite the silkscreen saying 100uF, that cap is a 47uF 1206 size (x 0.06" tall). Probably also 6.3V rated (cheapest), but maybe 10V if Aneng felt like splurging.I doubt the value is too critical as the higher value caps loose capacity at a few volts of bias, so 47uF seems reasonable, maybe even 22uF with a higher voltage rating.FWIW that cap is on the output of a boost converter generating 3.3V via a PW5100-33 IC.https://www.pwchip.com/en/file-download-2026-left.html

author: Paul T
author_rank: Regular Contributor
timestamp: February 17, 2025, 11:20:51 am
content: A soft switch combined with a single cell power source does not seem like a good idea. There will be a higher quiescent current than if they used two cells without the booster circuit and associated capacitors. It shouldn’t be up to the user to constantly remove cells or to spend the cost of the multimeter to source a better capacitor. Adding a power disconnect switch is another alternative.

author: Kean
author_rank: Unknown
timestamp: February 17, 2025, 01:08:02 pm
content: I bought my 2 x A3008 in about 2.5 years ago. They've been powered from the original AAA battery I installed when I got them and are still fine (currently 1.434V). I don't use these a lot, but I would say the quiescent current isn't really a problem.I measured the output of the boost converter when powered on, but I didn't check if it is still active after auto power off although I suspect it isn't. I am not going to pull it apart again unless I really have to.

author: Fungus
author_rank: Super Contributor
timestamp: February 17, 2025, 01:22:05 pm
content: Quote from: Kean on February 17, 2025, 08:25:30 amIn that case the boost converter must be running the whole time even when the power is "off".So there'll still be battery drain even if you replace it.(maybe not as much, but...)

author: Kean
author_rank: Unknown
timestamp: February 17, 2025, 02:22:08 pm
content: Quote from: Fungus on February 17, 2025, 01:22:05 pmWhy do you assume that?The boost converter has an enable pin that could be controlled by the main IC or some zero/low power circuit. If not enabled, then the incoming voltage will be passed through the inductor and diode to to the output, battery less the boost converter Schottky diode drop. There just needs to be some circuitry that can operate below about 1V to detect a power button press and enable the boost converter when required, and the main IC then holds the enable pin high until a timer expires.The 3.3V rail will likely be needed for several functions, in particular the backlight, but it doesn't have to be active in sleep mode. Low power circuitry like this is nothing new.

author: Fungus
author_rank: Super Contributor
timestamp: February 17, 2025, 02:45:36 pm
content: Quote from: Kean on February 17, 2025, 02:22:08 pmI was told it's on theoutputof the boost circuit.A boost circuit shouldn't be trying to maintain the output voltage when it's inactive.

author: Paul T
author_rank: Regular Contributor
timestamp: February 18, 2025, 01:01:17 pm
content: If there is high enough leakage, the boost converter might stay on? There are published articles on MLCC leakage current. It is reported that low voltage, high capacity caps are subject to increased leakage over time. My takeaway? Hard switches are much better than soft switches in battery operated devices, especially when in storage.

author: vladc77
author_rank: Regular Contributor
timestamp: March 01, 2025, 03:57:17 am
content: Great news! Replacing the 100µF SMD capacitor resolved the battery drain issue. Thanks again for everyone's assistance.The current measurements are now excellent:Turned on: 21.3 mATurned off: 0.016 mA

author: Kean
author_rank: Unknown
timestamp: March 03, 2025, 02:19:57 pm
content: Quote from: Paul T on February 18, 2025, 01:01:17 pmThe boost converter doesn't need to stay on for the leaky MLCC to drain the battery. When the boost converter is off, the battery voltage will pass through it un-boosted. In fact it will be dropped a little due to the series Schottky diode.I measured the operating and sleep current of my A3008 with my Keithley SMU set to 1.4V, and they were approx 25mA and 15uA. Assuming a typical alkaline AAA battery is about 1000mAh, then at 15uA sleep it will take over 7 years to drain the battery.Notably the beeper current is momentarily over 100mA, as with a 100mA current limit on the SMU the A3008 would lock up with the beeper stuck on and drawing 100mA when powering on & off. That shouldn't happen with a real battery. I set it to 300mA and it then powered on/off fine.