EEVblog #779 - How To Measure Product Battery Cutoff Voltage

[LabSpokane]

http://www.pcworld.com/article/2928997/batteriser-is-a-250-gadget-that-extends-disposable-battery-life-by-800-percent.html

Since we are accused of being secret agents of "Big Battery," I figured it would be worth re-linking this article. This article parallels every hallmark allegation of a "free energy" scheme:

- A technology so revolutionary, competitors will commit crimes to stop it

- The device will supposedly disrupt a large, stodgy industry.

- The people running that industry are either corrupt or incompetent.

- Said industry will conspire to keep this miracle from the people.

It's all so very familiar.  Never mind the facts. Never mind that these very large companies are able to hire very talented professionals who understand chemistry and tell the truth.

Then there is the accusation of folks like Dave, many others, and myself in speaking out about this. I will tell you my concerns:

- I object to the apparent abuse of academic credentials to argue from authority about a device that clearly is ineffective at best in most cases.

- I object to the claiming of inflated academic credentials. I refer to the supposed "Professor of Electrical Engineering" in the "Batteriser Buggers a Monkey" video who received his UNDERGRADUATE degree in 2014. 

- I object to Silicon Valley's adoption of the PT Barnum marketing model and financing these ridiculous ventures while kicking folks with more humble, but very viable business ideas to the curb.

- I object to the abuse of Corporate immunity in making these claims.

- I object to such ventures subsequently going public and convincing institutional investors to gamble people's retirement funds on magical thinking.

Notice how none of my objections have to do with a reduction in battery sales. If you must Bob, do continue to think I am an agent for "Big Battery."  That made my week. Thanks.

[TheElectricChicken]

PC world. how hilarious that they fall for that. I would hope that when people DO debunk this that they mention that you can recharge non-rechargeable batteries for about 8 times the life using much lower charge rates than normal, there are chargers built for it.

[FrankBuss]

I got another one for you.... Perhaps a little more OFFENSIVE. I've made a "few" adjustments!   

If you want to combine vector art and set up a T-Shirt Campaign, I'd like to donate ALL PROCEEDS TO DAVE to support his awesome EEVBlog!

Nice one, better than mine Anyone who wants to do another design, this is my Inkscape vector file: http://www.frank-buss.de/tmp/probes-the-monkey.svg And the 600 DPI PNG export: http://www.frank-buss.de/tmp/probes-the-monkey.png All public domain.

[edy]

I got another one for you.... Perhaps a little more OFFENSIVE. I've made a "few" adjustments!   

If you want to combine vector art and set up a T-Shirt Campaign, I'd like to donate ALL PROCEEDS TO DAVE to support his awesome EEVBlog!

Nice one, better than mine Anyone who wants to do another design, this is my Inkscape vector file: http://www.frank-buss.de/tmp/probes-the-monkey.svg And the 600 DPI PNG export: http://www.frank-buss.de/tmp/probes-the-monkey.png All public domain.

Couldn't have done it without you.... I'm sure it can be improved even more. We need something for the back of the shirt too! I love this crowd-sourcing a T-shirt for EEVBlog fans! We need to put something related to EEVBlog on the back so people can check out the site.

[Grapsus]

This batteriser story is getting ridiculous, they're like the group of people who insist on believing that the Earth is flat, anyone saying otherwise is a good guy but he's part of the conspiracy...

Have you seen this one on the same Batteroo channel ?



Another T-Shirt idea here !

[edy]

This batteriser story is getting ridiculous, they're like the group of people who insist on believing that the Earth is flat, anyone saying otherwise is a good guy but he's part of the conspiracy...

Have you seen this one on the same Batteroo channel ?
Another T-Shirt idea here !

Are you sure they are really twins? A bit of clever video editing and changing the hair style pulls off the trick nicely, using the same lady! In fact, we can have Dave do the same kind of "twin" commercial by having him put on a wig and doing the proper cuts and dialog and combining shots for the side-by-side when both "twins" are on the screen!

[AF6LJ]

This batteriser story is getting ridiculous, they're like the group of people who insist on believing that the Earth is flat, anyone saying otherwise is a good guy but he's part of the conspiracy...

Have you seen this one on the same Batteroo channel ?



Another T-Shirt idea here !

Oh GOD another BimBo with fake BooBs.

[edy]

Hey, the T-Shirt it looks pretty good on them! What do you think? 

[Svuppe]

On the serious side, I am currently running down a pair of NiMH cells in my Garmin eMap, logging the voltage with my new 34465A. Then we'll see if that result matches what I found using a lab supply, or not.

Well, that was interesting after all. Using a power supply, I consistently got shutdown voltages around 2.13 - 2.14V on my old GPS. But using batteries it lasted until 2.03V. Not a big difference, but still....

[edy]

Going along the lines of ARSETRONICS.... What about BUTTERISER! 

[rollatorwieltje]

On the serious side, I am currently running down a pair of NiMH cells in my Garmin eMap, logging the voltage with my new 34465A. Then we'll see if that result matches what I found using a lab supply, or not.

Well, that was interesting after all. Using a power supply, I consistently got shutdown voltages around 2.13 - 2.14V on my old GPS. But using batteries it lasted until 2.03V. Not a big difference, but still....

How did you connect the PSU to the GPS? Could be contact resistance. At 150mA that's about 0.6 ohms, that's a bit much but not entirely impossible.

[Svuppe]

How did you connect the PSU to the GPS? Could be contact resistance.

I used some standard wires with gator clips at one end. But I used the 34465A to measure the voltage directly at the battery terminals in the GPS also when using the PSU, so wire resistance should not be the issue.

[EEVblog]

Well, that was interesting after all. Using a power supply, I consistently got shutdown voltages around 2.13 - 2.14V on my old GPS. But using batteries it lasted until 2.03V. Not a big difference, but still....

So better, not worse 

[Red Squirrel]

This whole thing is hilarious.   I liked Dave pointing out the barely if unused Weller iron just sitting there, and the scope connected to it's own signal generator with a badly compensated probe.      They could have at least "proved" that the batteriser works by slipping it on the dead battery and then getting the monkey to work... I guess they tried off video, and it did not work. 

If I had to guess how they're getting their claim about cut off voltage being 1.3 or whatever, what they probably do is test a device until the battery dies and device shuts off, then test the battery.  Depending on the nature of the device when it dies it probably stops drawing any current at all, so the battery voltage will go back up.

As far as potentially adding any kind of circuitry like this in future batteries I don't think this would be a good idea.  Batteries are disposable, keep them as simple as possible, leave it up to the product being powered to implement this if it makes sense for that device.   For example a LED flash light could probably benefit from this as LEDs have a certain cut off voltage but don't draw much current so you could probably squeeze a bit more power out of the batteries.  But even then it would almost have to be a switch on the flash light that you turn on.  If you have a DC DC converter circuit running all the time it's probably going to waste more power than what you get back by using the last 5-10% of the battery.  Motorized devices on the other hand really can't benefit from this due to the sporadic current spikes.  At least, that's my noob opinion on the thing. I'm no EE professor.

[LabSpokane]

I have procured a Garmin etrex 20X GPS.  The Garmin Dakota is extremely similar aside from the etrex's lack of a touchscreen.  The battery save and backlight dimming features can both be deactivated in software, so there is no reason to construct an automated finger for testing.  Why Batteroo didn't simply read the manual and do the same will remain a persistent mystery.

Here is the initial data from testing the unit directly out of the box.  The etrex 20x uses two AA alkaline, lithium, or NiMH rechargeable batteries and has a mode setting for each such that the low battery warning functions appropriately.

Battery cutout voltages:

Alkaline Mode:  1.05V per cell

Lithium Mode:  1.29V per cell

NiMH Rechargeable Mode:  1.05V per cell

Notes:

- These are single data point readings.  I have not had time to do more. 

- These measurements were taken indoors with no GPS lock.  I am assuming that this is an equivalent condition under which Batteroo conducted this test.

- Screen brightness set to 100%

-  All power management functions disabled

- This device, without a doubt, already has a boost converter installed.  Here is a test run in alkaline mode, full screen brightness, no power conservation features

V          I (mA)   mW
================
3.2       147       470
3.0       150       450
2.8       160       448
2.6       172       447
2.4       188       451
2.2       207       455
2.1       218       458

This is clear evidence that adding a "Batteriser" type of external boost converter could only result in doubling up on converters and reduce the overall efficiency of the device.  This device is already engineered to maximize the depletion of a alkaline battery by operating in constant power mode. 

From looking through the GPS, I believe that there are numerous ways to alter the results of a rundown test.  I will be working on those next.  Simply by turning off the backlight, one can reduce the power draw by over 50%.  This can have a very dramatic effect on battery life as evidenced by the attached graph extracted from Duracell's MN1500 data sheet for AA alkaline batteries.  Changing the operating mode of the GPS such that its 450mW typical power use turns down to 220 mW, will change the expected operation time of the device from approximately 3 hours to over 8 hours.

In short, reducing the rate at which power is extracted from a battery is how to extract the absolute most energy from the battery.  Increasing the power draw, by doubling up boost converters is not a plausible method by which to extract more energy from a battery.  It is exactly the *wrong* direction one has to go in order maximize battery performance. 



More to come....

[AmmoJammo]

So it was most likely set to lithium for their test, which explains the 1.25 volt or so cut off that's I'd figured it also means that yes, of course the butteriser would increase the run time to what it should have been if the device was actually set right!

[LabSpokane]

So it was most likely set to lithium for their test, which explains the 1.25 volt or so cut off that's I'd figured it also means that yes, of course the butteriser would increase the run time to what it should have been if the device was actually set right!

I'm going to not make any speculations as to *how* the results were achieved until I have actually had time to do the testing.  So, please, don't read any more into what I've written than what I've written. 

[onlooker]

I am not sure if these were mentioned or not, I did some estimates based on Batteriser's current-vs-time plot. It is certainly questionable as to how they did the test.
 
1). At the 1.5 hour point when the GPS turned to the low power mode, the batteries consumed only about 200mAh to 300 mAh, which is about 10% to 15% of the battery's capacity.

2). The low power turning point is at about 1.3V (under load) based on a constant power consumption calculation.
       1.5V x 130mA / 150mA = 1.3V

[AmmoJammo]

Its completely obvious they had it in lithium mode. Lol

[FrankBuss]

I have procured a Garmin etrex 20X GPS.  The Garmin Dakota is extremely similar aside from the etrex's lack of a touchscreen.

Most likely it is a Garmin Approach G3: https://www.eevblog.com/forum/blog/eevblog-751-how-to-debunk-a-product-(the-batteriser)/msg732236/#msg732236

[AmmoJammo]

I have procured a Garmin etrex 20X GPS.  The Garmin Dakota is extremely similar aside from the etrex's lack of a touchscreen.

Most likely it is a Garmin Approach G3: https://www.eevblog.com/forum/blog/eevblog-751-how-to-debunk-a-product-(the-batteriser)/msg732236/#msg732236

Yeah, we figured that out 3 days ago :p

[LabSpokane]

I have procured a Garmin etrex 20X GPS.  The Garmin Dakota is extremely similar aside from the etrex's lack of a touchscreen.  The battery save and backlight dimming features can both be deactivated in software, so there is no reason to construct an automated finger for testing.  Why Batteroo didn't simply read the manual and do the same will remain a persistent mystery.

Unless it is the same it leaves open the question of what are the differences. So drawing comparisons from one to the other can't be done with the intention of refuting (or supporting) the original test results.

However, the question I wanted to ask you is, does the battery capacity meter seem to take into account the shallower and flatter NiMH discharge? Or does it seem to be strictly based on battery voltage.

This is the one clever thing Batteroo has done:  use a GPS that can't be purchased any longer.  I thought about this for a couple of days and thought buying a Dakota would be good enough.  It won't.  Nothing will.  There's a million excuses such as different settings, different firmware, not being in "golf mode," etc.  It will never end.  The Apple keyboard and trackpad are far easier because they are essentially modeless devices.  I am going to approach these tests from the point of view that this class of device will have to do certain things in order to run effectively off two AA batteries.  My plan is to test the device to show how it does those things.  This GPS and the Dakota/Approach shown in the Batteriser video have very similar battery lives.  The Dakota is rated at 20 hours.  The etrex 20x is rated at 25. 

I have already been in contact with Garmin and have a written statement about how they manage their devices' battery use.  I am going to continue to speak with them next week.  I have forwarded the claims made regarding their products by Batteroo, but it always takes a few days to get through engineering and legal.

I'm not even through the first test and it's looking pretty bad for the Batteroo runtime claims.  After 2:05 minutes of running the GPS at full tilt (everything turned out to maximum), the battery voltage is at 2.71V as measured directly at the battery terminals.  After the tests are complete, I will post the data.

And I'll tell you what I'm NOT doing.  I'm not dissipating power through an external current shunt during the test.  I've already demonstrated that the device runs in constant power mode, so monitoring the current is silly. 

Oh, and to answer your question, yes I will try to determine if the "fuel gauge" readings differ by battery chemistry.  There are only four status bars, so this will be very coarse, but I'm betting they do display differently according to chemistry.

[LabSpokane]

2.53V @ 4h51m

Hello Dr. Bob,

What did you do to make your GPS die in 2 hours?!  Enquiring minds want to know.  I haven't been able to kill this thing yet, and I'm REALLY TRYING. 

Oh that's right, I don't have an external resistor in series with the battery.  What was the value of your shunt resistor again? 

=======================
Oh, and I do need to thank you.  After all my prompting, you finally acknowledge the existence of Thevenin's Theorem.  That is just fantastic.  I'm only sad that you had to look it up on Wikipedia.  I know you're on sabbatical/summer vacation and brain dumps happen during those interludes, but don't you teach this stuff for a living...?



Maybe when you're back on the clock, we can talk about how you decided to choose an ESR that was off Duracell's chart by a fair margin. You're citing 0.5 ohm as a "typical" ESR.  That's really a bold assumption since the below graph shows it at 0.3 ohms at full discharge.  Then you spout off about 1.5 ohms, because of cold batteries.  Interesting, where's your environmental chamber for these tests, Bob?  If you're going to test in an office environment, let's use office environment data, shall we?

[AmmoJammo]

2.53V @ 4h51m

Hello Dr. Bob,

What did you do to make your GPS die in 2 hours?!  Enquiring minds want to know.  I haven't been able to kill this thing yet, and I'm REALLY TRYING. 

Oh that's right, I don't have an external resistor in series with the battery.  What was the value of your shunt resistor again?

You can only assume that they had it set to lithium so it shut down at 1.25 - 1.3volts per cell. 

http://www.ebay.com.au/itm/Garmin-G3-Touchscreen-GOLF-GPS-/331619569807?hash=item4d3611108f

Who wants to buy one for Dave!

[Svuppe]

Using a power supply, I consistently got shutdown voltages around 2.13 - 2.14V on my old GPS. But using batteries it lasted until 2.03V. Not a big difference, but still....

So better, not worse 

Exactly. If anything, it only helps the Batteriser that we are finding the cutoff voltage with a power supply instead of batteries.
But I'd really like to find out where that difference is coming from. It should be possible to get consistent data regardless of the power origin. The only thing I changed, apart from PSU to batteries, was my Fluke 187 that I had in series for current measurements while using my PSU. But that should not change anything, as I measured the voltage at the GPS battery clips like this: