ANENG A3009 pen multimeter drains the battery

[vladc77]

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?

[puxe]

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.

[csuhi17]

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?

What 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.

[Fungus]

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 "you need more than one multimeter!"

(preferably several more)

[vladc77]

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?

[csuhi17]

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?

so 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 you measure the current consumption?

[vladc77]

I'm going to get another multimeter and measure the current draw of the ANENG A3009 to see what's happening.

[Fungus]

Is it possible there's another way to manually power it off that doesn't cause this drain?

It's actually possible that it's faulty, and there's nothing you can do except remove the battery.

[Paul T]

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.

[vladc77]

Thanks for all the ideas and suggestions! I'll give that a try too, after my trip!

[vladc77]

I've finally been able to measure the current draw.  Here are the results:

Turned on: 62 mA
Turned off: 36 mA

These 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.

[Fungus]

Turned off: 36 mA

There's your answer!

[qbpm]

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.

[vladc77]

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?

[Fungus]

Try just removing it and see if it fixes the drain.

[vladc77]

Things are looking much better without the 100µF SMD capacitor!

Turned on: 20 mA
Turned off: 0.014 mA

I don't have any 100µF SMD capacitors on hand. I'm wondering if the voltage rating is critical in this particular application.

[qbpm]

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.

[Fungus]

Things are looking much better without the 100µF SMD capacitor!

Turned on: 20 mA
Turned off: 0.014 mA

I don't have any 100µF SMD capacitors on hand. I'm wondering if the voltage rating is critical in this particular application.

It'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.

[vladc77]

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.

[Paul T]

  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.   

[Kean]

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.

[Fungus]

Soft termination on MLCCs has become popular to help reduce these stresses.

Get one with legs and bodge it in. 

[Kean]

Get one with legs and bodge it in. 

They 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. 

[Fungus]

I meant one of those lentil-shaped ones. 

[Kean]

I meant one of those lentil-shaped ones. 

I 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