Design Con 2015
Breaking News
Comments
Oldest First | Newest First | Threaded View
Page 1 / 2   >   >>
Duane Benson
User Rank
Blogger
Battery or meter?
Duane Benson   6/16/2014 11:55:24 AM
NO RATINGS
This is really calibrating the measuring system. Is that correct? I've heard about this, but never had it explained clearly.

Some systems that I have list battery capacity as percent remaining. Others list it as time remaining. The challenge with using time as the measuring stick is, of course, that it's dependent upon the specific load.

I've seen some systems that appear to base the time left on the instantaneous load. If I turn up the brightness on the backlight, time left will drop and turning down the backlight does the opposite. Other devices seem to attempt to base the time left on the average consumption from full charge. It would be nice if all the systems were consistent.

The funny thing is that this really isn't a new problem. Every car I've owned has had a different accuracy curve for the gas gauge. It will move slowly for the first half of the gauge, then drop quite fast once indicating below half a tank. The gage does nothing to compensate for the difference in fuel consumption in the city vs. on the highway.

I understand that the car gage is simply attempting to display the quantity, not rage. Eventually, I get an internal sense for range. I kind of do the same with my electronic devices. I calibrate my head.

Duane Benson
User Rank
Blogger
Re: Battery or meter?
Duane Benson   6/16/2014 11:56:39 AM
NO RATINGS
Ivan - What's the most common battery display system used: battery capacity, or run time left? And, which do you find to be the most useful?

David Ashton
User Rank
Blogger
Another fine article....
David Ashton   6/16/2014 4:24:49 PM
NO RATINGS
HI Ivan - another fine artilce, thanks.

> Laptops and their batteries seem to be some of the worst offenders...

My work laptop - a Lenovo T510 which is showing its age in other respects - has a great battery with over 3 hrs life BUT best of all the run time indicator is almost bang on.  It is in time (hrs/min) which I reckon is the most useful indication (which answers Duane's question)  but switches to % when it is on charge.  I have never recalibrated it and it's only a couple of minutes out -if that - at the end of the battery life.  I guess I am lucky....

Are the ubiquitous computer memory "coin cells" - 2032 et al - Silver oxide or another chemistry?  They are nominally 3V so if Silver Oxide they'd have to be 2 cells in series so I suspect they are something else?

elizabethsimon
User Rank
CEO
Re: Another fine article....
elizabethsimon   6/16/2014 5:47:10 PM
NO RATINGS
The 2032 and similar 3V coin cells are a non-rechargable Lithuim chemistry. I used to know what one but can't remember the details right now. I guess we'll have to wait for a future article from Ivan...

 

David Ashton
User Rank
Blogger
Re: Another fine article....
David Ashton   6/16/2014 6:18:47 PM
NO RATINGS
Thanks Elizabeth.   I did look back to part 7 (Lithium Thionyl chloride - try saying that after a few drinks :-) but coin cells are not those I think.

I wait with bated breath for the next thrilling installment.  

Ivan - BTW some pics of typical batteries would be nice!

 

eetcowie
User Rank
Blogger
Re: Battery or meter?
eetcowie   6/17/2014 12:14:30 AM
NO RATINGS
Duane -- I really don't find either of the display systems more common than the other. The gas gauge is a coulomb integrator. Good ones also monitor the terminal voltage, and in this way can also tell when a battery is unserviceable. The game can be played that at the current rate the battery has this much left. Personally, I prefer the % capacity meter instead of time -- but this is because I have to deal with the non-linear battery (think of adding water to the flodded lead-acid cells during charging, to throw a kink in the total charge calibration, for example). We humans like to think of the world as balanced: if we take out half of the amount of charge from the battery when we start fresh, then put back the half we took out, then we want to be back at full charge again. But this doesn't give an accurate picture. Therefore, I will cover gas guages in a future post. That's cooking with gas!

eetcowie
User Rank
Blogger
Re: Battery or meter?
eetcowie   6/17/2014 12:19:12 AM
NO RATINGS
Duane: the calibration is for the measuring system, yes. It has to compensate for the fact that our world changes, and not for the better (be thinking -- entropy and such other random thoughts). Just a very very little piece of humor, there. But really, if everything always behaved in a well known/predictable manor, re-calibrating would not be needed.

Alas...

eetcowie
User Rank
Blogger
Re: Another fine article....
eetcowie   6/17/2014 12:24:35 AM
NO RATINGS
Elizabeth: the 2032 is a Lithium chemistry. There are a few variants of the specifics, but they are all primary batteries.

For examples of silver oxide, check here

http://www.energizer.com/batteries/Specialty/SilverOxide/Pages/default.aspx

 

eetcowie
User Rank
Blogger
Re: Another fine article....
eetcowie   6/17/2014 12:28:53 AM
NO RATINGS
David: yep, pics of batteries would be nice. I tend to shy away from showing one, for fear that someone take issue that the one I picked was a lousy non-representative sample, or some such. For the truely bizarre technologies, I will provide a pic or two, however.

eetcowie
User Rank
Blogger
Re: Battery or meter?
eetcowie   6/17/2014 12:34:46 AM
NO RATINGS
My good buddy in high school showed be why the car gas gauge is so non-linear -- when you look at the shape of the tank, it is rectangular (vertical walls) at the top, and then slopes at the bottom. A gauge that floats on top, is going to move faster at the bottom...simple as that. The simple fix for that is just to make the 'tick marks' for the remaining fuel be non-linear on the meter as well. Voilla.

Page 1 / 2   >   >>


Top Comments of the Week
Flash Poll
Like Us on Facebook

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Carlos Bueno

Adventures in Userland
Carlos Bueno
Post a comment
Editor’s Note: Excerpted from Lauren Ipsum: A story about computer science and other improbable things, author Carlos Bueno introduces us to Lauren and her adventures in ...

Max Maxfield

Tired Old iPad 2 vs. Shiny New iPad Air 2
Max Maxfield
9 comments
I remember when the first iPad came out deep in the mists of time we used to call 2010. Actually, that's only four years ago, but it seems like a lifetime away -- I mean; can you remember ...

Martin Rowe

Make This Engineering Museum a Reality
Martin Rowe
Post a comment
Vincent Valentine is a man on a mission. He wants to make the first house to ever have a telephone into a telephone museum. Without help, it may not happen.

Rich Quinnell

Making the Grade in Industrial Design
Rich Quinnell
16 comments
As every developer knows, there are the paper specifications for a product design, and then there are the real requirements. The paper specs are dry, bland, and rigidly numeric, making ...

Special Video Section
The LT8640 is a 42V, 5A synchronous step-down regulator ...
The LTC2000 high-speed DAC has low noise and excellent ...
How do you protect the load and ensure output continues to ...
General-purpose DACs have applications in instrumentation, ...
Linear Technology demonstrates its latest measurement ...
10:29
Demos from Maxim Integrated at Electronica 2014 show ...
Bosch CEO Stefan Finkbeiner shows off latest combo and ...
STMicroelectronics demoed this simple gesture control ...
Keysight shows you what signals lurk in real-time at 510MHz ...
TE Connectivity's clear-plastic, full-size model car shows ...
Why culture makes Linear Tech a winner.
Recently formed Architects of Modern Power consortium ...
Specially modified Corvette C7 Stingray responds to ex Indy ...
Avago’s ACPL-K30T is the first solid-state driver qualified ...
NXP launches its line of multi-gate, multifunction, ...
Doug Bailey, VP of marketing at Power Integrations, gives a ...
See how to ease software bring-up with DesignWare IP ...
DesignWare IP Prototyping Kits enable fast software ...
This video explores the LT3086, a new member of our LDO+ ...
In today’s modern electronic systems, the need for power ...