New EEVblog BM786 Multimeter

[NoisyBoy]

I would say in low drain devices, the probability for battery leakage is far from low because the batteries tend to stay in the device for a long time.  I would say in my case, leakage is not an if, but just a matter of time, especially for Duracell batteries.  On average, I see leakage in over 50% of my low drain devices with Duracell.  Handheld DMM will fall in the category, so I have long switched over to Eneloop as Fungus has suggested.  The only place I use alkaline is children toys that tends to use up the batteries in weeks.  Eneloop is a low low price to pay to prevent battery leakage from ruining a piece of equipment.

[J-R]

I have dozens of the Eneloop Pros and white 10-year.  They all have quite a bit less capacity than alkaline at low currents.  I do use them in my Fluke 287 and other similar devices where it makes good economic sense. Going back maybe 40 years I can count on one hand the number of alkaline cells that have leaked  and none caused any permanent damage.  But of course that is just my experience.

[joeqsmith]

What is the expected BATTERY LIFE for the BM786 with fresh Alkaline batteries, backlight off? 

We know the 121GW is 500 hours with BT and the backlight off, so I'm curious about the BM786.

For the 121GW, I measured 443 hours and 156 hours for the 789.  The 786 came in at 118 hours.   You can find that spreadsheet on-line or watch the review.  There are also posts were we have discussed the assumptions I have made when making these measurements. 

[EEVblog]

For the 121GW, I measured 443 hours and 156 hours for the 789.  The 786 came in at 118 hours.   You can find that spreadsheet on-line or watch the review.  There are also posts were we have discussed the assumptions I have made when making these measurements.

I'm doing a video on this now. More as a generic thing, but the 786 is the example for battery estimation.

[NoisyBoy]

J-R, I completely understand your point and respect it.  I just wish I am just as lucky with alkaline batteries. 

Back to the BM786, Dave, I do find the meter a joy to use.  Fluke used to be my default for handheld, but since I liked the BM786 so much, I just ordered a BM869s.  There is never enough DMM for us addicts, although upon opening the 869s after its arrival, I have a feeling that the 786 would still be my preference due to its smaller form factor, besides, I love that EEVBlog logo and the blue!

I have dozens of the Eneloop Pros and white 10-year.  They all have quite a bit less capacity than alkaline at low currents.  I do use them in my Fluke 287 and other similar devices where it makes good economic sense. Going back maybe 40 years I can count on one hand the number of alkaline cells that have leaked  and none caused any permanent damage.  But of course that is just my experience.

[EEVblog]

although upon opening the 869s after its arrival, I have a feeling that the 786 would still be my preference due to its smaller form factor, besides, I love that EEVBlog logo and the blue!

I don't like big meters like the 869 on my bench unless it's for something specific.

[joeqsmith]

For the 121GW, I measured 443 hours and 156 hours for the 789.  The 786 came in at 118 hours.   You can find that spreadsheet on-line or watch the review.  There are also posts were we have discussed the assumptions I have made when making these measurements.

I'm doing a video on this now. More as a generic thing, but the 786 is the example for battery estimation.

I made a source meter that makes these measurements automatically.  The spreadsheet includes the raw measured values and I would expect you to have similar results.   If you find that you are getting different results and have questions about the data I collected, feel free to ask for further information. 

[J-R]

Surely there will be some minor power draw variances between one unit to another within a specific product's life cycle due to component variations or substitutions.

Oddly, my BM789 draws about 6.5mA from 4.8V to ~4V, at which point it actually drops a little to 6.3mA down to 3.7V.  (VDC switch position)

My 121GW varies from about 5.8mA to 6.2mA depending on function, and does not appear to be voltage dependent (4V-6.4V).

So that puts the BM789(all BM78x?) perhaps closer to 175 hours of runtime and the 121GW to 515 hours, based on the arbitrary 1,150mAh and 3,000mAh battery ratings I mentioned earlier.

The 121GW only adds another 10mA when the backlight is on compared to the BM789 which adds another 30mA.  So that is ~200 hours total for 121GW and ~30 hours total for BM789.

[EEVblog]

Surely there will be some minor power draw variances between one unit to another within a specific product's life cycle due to component variations or substitutions.

A little bit, but battery difference and temperature too should be the biggest variables.

Oddly, my BM789 draws about 6.5mA from 4.8V to ~4V, at which point it actually drops a little to 6.3mA down to 3.7V.  (VDC switch position)

Mine draws 5mA in DCV, 9mA in DC+AC. 42mA with the backlight on.

[EEVblog]

[Fungus]

I would say in my case, leakage is not an if, but just a matter of time, especially for Duracell batteries.  On average, I see leakage in over 50% of my low drain devices with Duracell.

Going back maybe 40 years I can count on one hand the number of alkaline cells that have leaked  and none caused any permanent damage.  But of course that is just my experience.

The plural of "anecdote" is not "evidence", the truth probably lies somewhere in the middle.

Me? I wouldn't store alkaline batteries inside an expensive device.



(my theory is that they mostly leak when the device is kept in a dark place)

[rsjsouza]

My latest theory is that they are not potty trained: when left alone for too long, they fall asleep and wet their pants.

[NoisyBoy]

My experience with them is more like exploded diapers with my kids when they were babies, especially when I forget to check and change the diapers regularly.

My latest theory is that they are not potty trained: when left alone for too long, they fall asleep and wet their pants.

[JDW]

I wouldn't store alkaline batteries inside an expensive device.

Define "store". 

If you use a Multimeter once a week, it is deemed "regular use" and not "storage" and yet it is infrequent enough the batteries may last a couple years or more.  Or does the sheer act of switching it on once a week over the course of a few years prevent the spewing of battery guts, as opposed to storing it for the same length of time without switching it on at all, or switching it on but once or twice during that same span of time?

[J-R]

NiMH has some negatives compared to alkaline:

Cost effectiveness: on a device that could go 5-10 years on a single set of batteries, selling all of those with rechargeable batteries + charger is going to greatly increase the price.  This is especially true if the device is low-cost and more of a disposable type of product (rather than something to be repaired).

Self-discharge/capacity: this has been an issue for quite some time, especially for those of us who have had to deal with that since the dawn of time.   You never were quite 100% sure whether the rechargeable cell was going to perform as expected when you grabbed it.  A fresh alkaline cell out of the package was a near-guaranteed, known quantity.  For the popular NiMH option (eneloops: regular, pro & lite) you must choose between conflicting characteristics of capacity, self discharge rate and cycle life.

Multi-cell configurations: odds are good of having one NiMH cell with a reduced capacity and this means the device doesn't run as long as expected.  Unless you're regularly characterizing your cells and binning them by capacity, you are looking at a reduction of the runtime compared to alkaline in addition to the reduced design capacity.  This is not insignificant.

Managing NiMH cells on a daily basis: this is not trivial and there are a lot of factors to consider.  Just have a look at the official FAQ here: https://www.panasonic.com/global/energy/products/eneloop/en/lineup/eneloop.html
So if you were to sell a device with NiMH and a charger, you now have to explain a lot more to the consumer, and design the device to handle NiMH as well as perhaps alkaline or even lithium.


For alkaline, the big risks for leakage is in a multi-cell configuration, and/or where the device continues to draw power when off.  Even when operating, you have a good chance that one cell will fully discharge before the others and the user or the device does not realize this.  Then the fully discharged cell may leak if left this way for long periods.  This can also happen of course when the device is just sitting and slowly discharges all the cells.  One may go dead before the others and leak.

Many alkaline cell manufacturers have made improvements over the years to reduce leakage, and advertise this.  There are also a significant number of variables that can impact the health of alkalines, such as the environmental conditions the battery experienced, both during storage and usage.  I believe all the manufacturers suggest "cool & dry" when possible.


With that said, I think eneloops in the Fluke 287/289 is a no-brainer, as I mentioned previously.


The BM78x might actually be a reasonable candidate for a lithium-ion pouch cell.  Having the low-battery indicator come on at 3.7V doesn't seem too terrible.

[JDW]

...the fully discharged cell may leak if left this way for long periods.  This can also happen of course when the device is just sitting and slowly discharges all the cells.  One may go dead before the others and leak.

This pertains to my yet unanswered question put forth in my previous post.  Define "storage" and "long periods".

Again, what if I use my meter once a week?  What about using it once every two weeks?  Is that "storage"?  Is that "long periods"? 

How often must we power on the meter to avoid battery leakage? 

Will the batteries leak even if we actively use the meter?  If not when we actively use it, then we need to define what "actively use it" means.  In other words, if the sheer act of powering on the meter prevents battery leakage, how often must that be done?  And if one argues that the batteries would still leak even if the meter is used often, as defined as once a day, then all the talk of "when stored" or "when not used for long periods of time" goes out the window.

[J-R]

"Using" it doesn't prevent leaking.  It has nothing to do with that (other than maybe replacing the batteries more often).  Nor does "storing" it.  It's just certain conditions may align such that a discharged (primarily) cell will have a higher chance of leaking.  I found a multi-cell device the other day in my garage that has been in a sealed/cool/dry place for decades and the Energizer batteries were completely dead but hadn't leaked at all.  Then there are folks posting photos of new batteries leaking in the package (could have been exposed to high heat).

I think it's reasonable to say if you are not going to use something for years or decades, then take the batteries out, and if the device has any amount of current draw when off, then don't store it longer than a period of time that will cause the batteries to be fully discharged.

[Black Phoenix]

Rule of thumb for me is if the device is not going to be used in a while, batteries are off (if they are not Ni-CD/Ni-NH or Lithium or internal battery) and stored away from the equipment.

I almost lost a 54II by leaked Duracell Procell (was siting batteries down on the case, had to replace battery contacts and clean corrosion on the PCB main IC legs, that were starting to desintegrate itself had I caught later) and my 289 (didn't leaked but changes on the ends of the batteries were already showing).

Now all battery equipment I have run Eneloops White or Pro and GP Battery Lithium (for the 9V PP3 in the 87V).

But even the Lithium I'm always checking time to time afraid it may bulge. We advanced so much in battery tech in 20 years but still reliability is something we still are way back in the 90s...

[JDW]

...don't store it longer than a period of time that will cause the batteries to be fully discharged.

Based on that comment, we see the reason that "active use" (which for now I shall define is being at least ONCE A WEEK) saves our devices from destruction is because at some point we will see a low battery indication and either change the batteries then or change them when the meter no longer works, thereby preventing a situation where totally dead batteries are left in the device for more than a week.  This would be why "active use" prevents spewed battery guts.

[tautech]

Really guys, nothing has changed in years. 
This is certainly not the oldest a quick search could find, from 2016:
https://www.eevblog.com/forum/chat/leaking-aa-and-aaa-batteries/

[J-R]

Yay, a rant thread, nobody ever exaggerates or fibs in those...

Back to something more on topic, after watching Dave's latest video I tested my BM789(05) again with more precision and at 4.500V the 1 minute average current draw was 6.433mA in DCV mode.

[AVGresponding]

...don't store it longer than a period of time that will cause the batteries to be fully discharged.

Based on that comment, we see the reason that "active use" (which for now I shall define is being at least ONCE A WEEK) saves our devices from destruction is because at some point we will see a low battery indication and either change the batteries then or change them when the meter no longer works, thereby preventing a situation where totally dead batteries are left in the device for more than a week.  This would be why "active use" prevents spewed battery guts.

All well and good, but these leak-tubes will often start their evil work before the voltage drops enough to give such a warning.

[JDW]

...these leak-tubes will often start their evil work before the voltage drops enough to give such a warning.

Which suggests that even "active use" isn't enough to prevent battery leakage, so I guess we might as well throw in the towel if that is in fact true.

[AVGresponding]

I moved to using rechargeables some years ago now. I have a few devices that still have primary PP3s but I'm slowly acquiring Li-ion versions of those too (they aren't cheap so it's slow...)

[BillyO]

Use lithiums.  Problem solved.  And yes, they work fine in this meter (and every other meter I have).

Do no use NiMH in this meter.  Their nominal voltage is 1.2V, that is the voltage this meter gives a low battery warning.  Well, you can use them, but you will be doing a lot of charging.