From: Ron Hunter on
SMS wrote:
> Ron Hunter wrote:
>
>> Isn't a battery meter on a device using NiMH batteries rather like a
>> radar detector with such a short range that it only tells you you have
>> been caught? Given the discharge curve, it need only be a dot in the
>> LCD display that says your battery is below the cutoff voltage.
>> Still, my camera do have such a warning, and it really means what it
>> says because only a couple of pictures can be taken with that warning
>> on before ugly things start to happen.
>
> Yes, that's currently the case. It's too expensive for a manufacturer to
> integrate a pulse-load type of battery tester into an AA powered camera,
> especially since they couldn't charge extra for it since so few users
> would understand that it's something that's worth an extra couple of
> dollars.
>
> It's more like the oil pressure light on a car. Rather than being
> labeled "Oil," which many people believe means that they need to add oil
> soon, or have an oil change, the manufacturer should label it "$5000
> unless you stop NOW."

I HATE warning lights not accompanied by gauges. The amount of oil
pressure needed to prevent engine damage is usually far below the
setting for the oil pressure warning light. I could have avoided an
expensive tow charge had I had a gauge on my Honda some years ago. Oil
pressure is much too important a thing to trust to a stupid 'idiot
light'. As it turned out, I COULD have continued to drive the car
safely, but without a gauge, I didn't know that.
From: Ron Hunter on
ASAAR wrote:
> On Tue, 26 Jun 2007 04:13:25 -0500, Ron Hunter wrote:
>
>>> Sorry, but when I pointed out your inaccuracies and misstatements,
>>> well before you started using your filter, you never even attempted
>>> to disprove any of my corrections. You simply ignored them and
>>> continued spouting the same inaccurate facts. It's *you* that needs
>>> to change your ways, but I'll be quite surprised if you do. We can
>>> start with one of your repeated points of misinformation, that
>>> cameras don't or can't have battery meters for NiMH cells due to
>>> their supposedly flat discharge curve. There's plenty of evidence
>>> that that is untrue, and I could repeat some of the reasons for you
>>> if you're willing, but I'm amazed that a self-proclaimed "battery
>>> expert" wouldn't know this already.
>>>
>> Isn't a battery meter on a device using NiMH batteries rather like a
>> radar detector with such a short range that it only tells you you have
>> been caught? Given the discharge curve, it need only be a dot in the
>> LCD display that says your battery is below the cutoff voltage. Still,
>> my camera do have such a warning, and it really means what it says
>> because only a couple of pictures can be taken with that warning on
>> before ugly things start to happen.
>
> Not at all, and I see that the spouter of disinformation has
> already chimed in to support this erroneous view of yours. In
> addition to the highly accurate 14 segment LCD display that I have
> on one of my radios, which unfortunately you can't see, but which
> would corroborate the accuracy of NiMH battery meters, there are two
> other devices that convincingly show that you're mistaken.
>
> First, I had Palm PDAs that ran battery meter software which had
> calibration settings for alkaline, NiMH and Li-Ion batteries.
> Several used two AAA batteries and another used either four AAA
> batteries or a Li-Ion battery pack. The voltage was displayed by
> the software to 0.01 volt, and the warning level triggered at 2.10
> volts for the two AAA PDAs (which could be user modified) and the
> current voltage was always displayed in a tiny font on the screen.
> Battery life was about 50 hours and when the warning triggered at
> 2.10 volts, the PDAs easily had more than 10 hours of battery life
> remaining, since the PDAs could still operate until the voltage
> dropped slightly below 1.90 volts. Using alkaline batteries, that
> was no problem. Using NiMH batteries, the voltage would quickly
> plummet after 2.00 volts was reached. But until that 2.00 volt
> threshold was reached, each 0.01 volts was good for about one hour
> of battery life, both for alkaline and NiMH batteries. This battery
> meter was extremely accurate and reliable. Being able to predict
> the end of a 50 hour battery life to within a couple of minutes is
> probably good as any high tech. Li-Ion battery meter has ever
> achieved.
>
> The other example is one which you and many others may be familiar
> with. My last several cell phones used Li-Ion batteries, and they
> all used a multi-segment vertical display to show both the signal
> strength and the battery level. Several previous cell phones used
> NiMH batteries and had the same type of signal strength and battery
> meters. They both performed about the same, with the segments
> winking out at a uniform rate over the 6 to 7 days worth of life
> each battery charge was good for. The NiMH batteries did NOT cut
> out without a warning as you suggested. There was absolutely no
> difference between how the battery meter worked, for both NiMH and
> Li-Ion batteries. Anyone that has used cell phones for more than
> the last couple of years probably has used models that worked with
> NiMH batteries. I highly doubt that I'm the only one that had
> models with decent battery meters.
>
> There is *no* reason why decent battery meters can't be designed
> into cameras that use NiMH AA batteries. If you've only used
> devices that show tiny, virtually useless dots, or warnings that
> come so late that they didn't provide enough warning time, that's
> the fault of the device's designers, and they did a poor job.
> Similarly, if your camera does "ugly things" only several shots
> after the warning appears, that also indicates poor design, unless
> I'm misinterpreting what you said. A well designed camera should do
> an orderly shutdown well before any type of battery gives out. If
> yours doesn't, the camera's designers were incompetent. I suspect,
> though, that you're just talking about experiencing an orderly,
> intentional shutdown, and not something like losing power after a
> shot but before the image was completely written to the flash card.
> That, I agree, would be pretty "ugly".
>

The symptom exhibited by my last camera was a shutoff of the flash
operation, completely, followed by a period of being able to take
flashless pictures (20 or so), and then shutdown during writing to the
flash card. I, luckily, lost only the single picture, but had this
happened while writing to the FAT, I would most likely have lost the
whole card's contents.
My current camera warns of low battery, and then just refuses to take
more pictures when shutoff point approaches. A better solution, in my book.
From: Thomas T. Veldhouse on
SMS <scharf.steven(a)geemail.com> wrote:
> Thomas T. Veldhouse wrote:
>> SMS <scharf.steven(a)geemail.com> wrote:
>>> Yes, that's currently the case. It's too expensive for a manufacturer to
>>> integrate a pulse-load type of battery tester into an AA powered camera,
>>> especially since they couldn't charge extra for it since so few users
>>> would understand that it's something that's worth an extra couple of
>>> dollars.
>>>
>>
>> As I indicated and you failed to read, pulse load only helps if the battery is
>> NOT health. Voltage is plenty sufficient for a healthy battery.
>
> No it isn't. To show remaining capacity based on NiMH voltage, you have
> to measure within 5/100ths of a volt, and the remaining capacity varies
> by both temperature and discharge rate, so you need an extremely
> accurate, temperature compensated voltage reference. Since the batteries
> in a camera are in series, you don't know if one battery is skewing the
> voltage up or down. If you only measure to 1/10th of a volt then the
> error is so high that it's a worthless measurement.
>

Remaining capacity on a LiIon also varies by temperature and discharge rate.
You aren't building yourself a case here.

> There are two common ways of accurately measuring capacity on NiMH
> batteries. One is the pulse load test, and one is coulomb counting. The
> latter is very complex and is normally used only on very expensive
> equipment, and even the former is too complex and expensive to implement
> in a consumer device.
>

For God's sake, you didn't even know about pulse load testing until I told you
about it and gave you a link to that tester. As far as coulomb counting goes,
it is not specific to ANY type of battery. Coulomb counting is simply a
measurement of current, which is not useful in a device as an indicator
anyway. "On the other hand, measuring and recording the amount of current that
is discharged from the battery, or coulomb counting, has its drawbacks because
it assumes that the battery begins with full capacity, which is not always the
case because a battery's initial capacity is affected by age and other
factors. It also assumes that the battery will be able to actually deliver its
capacity at the necessary rate. "

http://thomas-distributing.com/articlelive/articles/31/1/ZTS-Inc---Battery-Tester-Technology-Article/Page1.html

Perhaps what you were reading is that article about using coulomb counting for
measuring the signal current in GSM/GSRP applications?

http://www.maxim-ic.com/appnotes.cfm/appnote_number/1798

Anyway, it appears you like to Google and simply have a desire to no be wrong
about NiMH batteries, especially the modern low discharge variety.


> Li-Ion batteries have a fairly linear voltage discharge curve. Even
> measuring to only 0.2 volts will give a good indication of remaining
> capacity.
>
> Look at the Maxim application note,
> "http://www.maxim-ic.com/appnotes.cfm/an_pk/121".
>
> Since there appears to be some confusion over the capacity versus
> voltage issue I've added two graphs to the website that show remaining
> capacity versus voltage, one for NiMH and one for Li-Ion.
>

I will leave you too it as there is clearly no real point of continued
discussion.

--
Thomas T. Veldhouse

Eat drink and be merry, for tomorrow they may make it illegal.

From: SMS on
Ron Hunter wrote:

> I HATE warning lights not accompanied by gauges. The amount of oil
> pressure needed to prevent engine damage is usually far below the
> setting for the oil pressure warning light. I could have avoided an
> expensive tow charge had I had a gauge on my Honda some years ago. Oil
> pressure is much too important a thing to trust to a stupid 'idiot
> light'. As it turned out, I COULD have continued to drive the car
> safely, but without a gauge, I didn't know that.

An ideal addition would be an audible alarm for both temperature and oil
pressure. My nephew did about $12,000 damage to his four year old BMW X5
SUV by not heeding the temperature gauge (leaking water pump). Most
vehicle owners don't have the slightest idea of how an engine is cooled
or lubricated, or what the gauges mean, but they are used to alarms for
emergency situations.
From: SMS on
Thomas T. Veldhouse wrote:

> Remaining capacity on a LiIon also varies by temperature and discharge rate.
> You aren't building yourself a case here.

Sure I am. The difference is in the voltage curve. The Li-Ion pack
declines linearly with capacity over a greater range. It's much cheaper
to measure in 0.2V increments than 0.05V increments.