On Jun 21, 12:33*pm, Bodincus wrote:
(20/06/10 04:41), Chris Blunt:

On Fri, 18 Jun 2010 14:32:52 +0100,
wrote:

(18/06/10 13:58), Chris Blunt:
On Fri, 18 Jun 2010 13:31:24 +0100,
wrote:

B) However, that proves my point. The relationship between voltage and
residual power is non-linear, and the residual power inside the battery
- whatever type it is - *is not related to the voltage between the dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?

What else could they measure?
During idle time, small bursts through a fixed resistance circuit to
measure both voltage (and its drop under load), and current.
A bit of computation and you can measure how much oomphf the cell has left.

The additional components required to do that will all add additional
cost and weight to the device, as well as further draining the
battery. It doesn't make much sense to unnecessarily put extra load on
a battery when what you are trying to achieve is to squeeze as much
life out of it as possible.

One SMD resistor and a bit more software in the device would add costs?

Maybe not, but the transistor to switch the resistor in and out and
the ADC to measure the current might.

MBQ

"spacecadet" wrote in message
...

Are 'modern' DAB radios designed to work with the lower voltage you get
from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried
it lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't
last long on rechargeables - maybe only an hour or two. After that, it
will keep going for some time on FM.

You're thinking of NiCads. NiMhs are 1.5V.

Ummm nope, NiCad's are nominally around 1.25v
NiMH nominally around 1.35v

Steve Terry
--
Welcome Sign-up Bonus of £1 when you signup free at:
http://www.topcashback.co.uk/ref/G4WWK

"Steve Terry" wrote in message
...
"spacecadet" wrote in message
...

Are 'modern' DAB radios designed to work with the lower voltage you get
from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried
it lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't
last long on rechargeables - maybe only an hour or two. After that, it
will keep going for some time on FM.

You're thinking of NiCads. NiMhs are 1.5V.

Ummm nope, NiCad's are nominally around 1.25v
NiMH nominally around 1.35v

NiMH cells say 1.2V on them.

And indeed I observe pretty much the same average voltage during the
discharge cycle averaging about 1.25V.
NiMH may start slightly higher than NiCads but they very quickly drop to
pretty much the same voltage as NiCad.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

Steve Terry wrote:
"spacecadet" wrote in message
...
Are 'modern' DAB radios designed to work with the lower voltage you get
from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried
it lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't
last long on rechargeables - maybe only an hour or two. After that, it
will keep going for some time on FM.
You're thinking of NiCads. NiMhs are 1.5V.

Ummm nope, NiCad's are nominally around 1.25v
NiMH nominally around 1.35v

Steve Terry

Nominal voltage for both is around 1.2v per cell median discharge, 1.4
fully charged.

Brian Gregory [UK] wrote:
"Steve Terry" wrote in message
...
"spacecadet" wrote in message
...
Are 'modern' DAB radios designed to work with the lower voltage you get
from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried
it lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't
last long on rechargeables - maybe only an hour or two. After that, it
will keep going for some time on FM.
You're thinking of NiCads. NiMhs are 1.5V.

Ummm nope, NiCad's are nominally around 1.25v
NiMH nominally around 1.35v

NiMH cells say 1.2V on them.

And indeed I observe pretty much the same average voltage during the
discharge cycle averaging about 1.25V.
NiMH may start slightly higher than NiCads but they very quickly drop to
pretty much the same voltage as NiCad.

They are virtually identical. both will take a surface charge up to
maybe 1.5v per cell, but it only last seconds..

Bodincus wrote:

During idle time, small bursts through a fixed resistance circuit to
measure both voltage (and its drop under load), and current.
A bit of computation and you can measure how much oomphf the cell has left.
BTW, I hereby claim Intellectual Property for this idea.

This is essentially the strategy used by battery powered smoke alarms.
The LED flash is actually there to provide the load. They only measure
on load voltage.