From: SMS on
Thomas T. Veldhouse wrote:
> NiMH are OFTEN packaged together in the same way as
> LiIon packages are sold. Consider the cordless phone in many peoples' homes.
> These are almost exclusively NiMH batteries [in two or three cell packages]
> and they typically take a 0.1C or even 0.05C trickle charge when left on the
> charger. Why NiMH? Because they will last longer so fewer people have issues
> with their phones not holding a charge during the warrantee period.

The one's I've opened up to do battery replacement were always Ni-Cad.
Either the Ni-Cads were cheaper, or the manufacturer wanted the larger
number of charge/discharge cycles at the expense of shorter talk time,
or it was because Ni-Cads accept trickle charging better. As Isador
Buchmann writes in _Batteries in a Portable World_: "Remove the battery
when ready because any prolonged trickle charging will damage the
battery. The caution applies especially to NiMH because this chemistry
cannot absorb overcharge well."


From: Thomas T. Veldhouse on
SMS <scharf.steven(a)geemail.com> wrote:
> Thomas T. Veldhouse wrote:
>
>> 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.
>
> Huh? One of my chargers has a slot that does pulse-load testing. I've
> known about it for quite a while.

Which charger is that?

--
Thomas T. Veldhouse

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

From: Thomas T. Veldhouse on
SMS <scharf.steven(a)geemail.com> wrote:
> Thomas T. Veldhouse wrote:
>> NiMH are OFTEN packaged together in the same way as
>> LiIon packages are sold. Consider the cordless phone in many peoples' homes.
>> These are almost exclusively NiMH batteries [in two or three cell packages]
>> and they typically take a 0.1C or even 0.05C trickle charge when left on the
>> charger. Why NiMH? Because they will last longer so fewer people have issues
>> with their phones not holding a charge during the warrantee period.
>
> The one's I've opened up to do battery replacement were always Ni-Cad.
> Either the Ni-Cads were cheaper, or the manufacturer wanted the larger
> number of charge/discharge cycles at the expense of shorter talk time,
> or it was because Ni-Cads accept trickle charging better. As Isador
> Buchmann writes in _Batteries in a Portable World_: "Remove the battery
> when ready because any prolonged trickle charging will damage the
> battery. The caution applies especially to NiMH because this chemistry
> cannot absorb overcharge well."
>

And I just pointed out that they DO accept the very low trickle charge fine,
which is why they use them and which is why they use NiMH. NiCd is gone with
the ice age for most uses. Super high drain devices still use them because
there is less resistance in a NiCd battery [i.e. for a power drill]. There is
no real problem with throwing NiMH batteries in the dump as there is with
NiCd, which is probably another driving force [but then again, nobody should
be throwing their cordless phones in the trash either].

I just opened my VTech phone and the battery says 3.6V 600mAh Ni-MH. Clearly
three AAA cells in the package. I could just open it up and put in three
900mAh cells and get better capacity. Oh yes, on the otherside, it says
please charge battery for a minimum of 16 hours prior to use. That suggests
to me a maximum charge rate of 0.1C and I suspect it is less than that.

--
Thomas T. Veldhouse

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

From: SMS on
Thomas T. Veldhouse wrote:
> SMS <scharf.steven(a)geemail.com> wrote:
>> Thomas T. Veldhouse wrote:
>>
>>> 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.
>> Huh? One of my chargers has a slot that does pulse-load testing. I've
>> known about it for quite a while.
>
> Which charger is that?

It's the Sanyo that Costco used to sell. It has one of the four
positions that you stick a battery in, and wait five seconds for the
pulse load test to complete, and it indicates the approximate remaining
capacity (80% or more, 50-80%, or less than 50%). Not as good as the
standalone tester, but useful when you have a bunch of batteries where
you have no idea of the charge level.

See page 8 of "http://us.sanyo.com/batteries/pdfs/MQH01_manual.pdf"
under "Battery Capacity Indicator."

Unfortunately, Costco dropped this product, and now sells a much less
capable Duracell charger and batteries. Costco once sold a Panasonic
charger that was kind of neat because you could charge off of a USB
port. Unfortunately it had a tendency to get so hot that it melted the
plastic of the charger and was recalled,
"http://www.costco.com/Service/FeaturePage.aspx?ProductNo=11027463").

From: SMS on
SMS wrote:

> A low battery warning indicator that works passably well across the
> different battery types is possible, but forget about a gauge that
> provides any accurate information. It's like measuring with a
> micrometer, marking with a crayon, and cutting with an axe.

I added graphs of Li-Ion, NiMH, and Alkaline voltage versus capacity,
using the same voltage scale (4 packs of AA cells, 7.4V Li-Ion pack).
This gives a good visual picture of why the AA powered cameras generally
have only a low-voltage indicator. You'd need so much circuitry and
intelligence to deal with different battery types that it's impractical
to implement.

Steve
http://batterydata.com
(Google "battery data unbiased nimh li-ion" and then click on "I'm
Feeling Lucky" and it'll take you to the web site).