Can replace Lthium with Nimh external battery pack?

On Friday, October 2, 2015 at 4:47:55 PM UTC-7, Jeff Liebermann wrote:

If you don't care about efficiency, a linear current source is good
and cheap. However, if you want your light to have a constant light
output (until the battery quits) and for your battery to last, one of
several types of switchers work better with the added bonus of
brightness control.

Both phosphorus and switched supplies reduces the brilliance of the light.

The Cree XM-L LED typically runs at 1.5 to 2.0A average current. At
0.6v drop in your current source, that's 0.9 to 1.2 watts in heat.
That's not a huge amount, but it's still wasted power.

I'm sort of confused - you're saying the same thing as I did but quoting spec sheets which most people can't read. Is there some reason for that?

The question was whether there was a cheaper replacement for the Lithium Ion battery and a quick off-the-cuff reply was YES there is.

If you want to argue spec sheet figures to three decimal places doesn't that ignore the question? Do you wish to discuss recharging rates and their effects on battery life? Is that any more to the point?

I spent 40 years building everything from the first heart/lung machine to the automation of PCR to get HIV out of the blood banking system (and then be used to analyze DNA) to increasing the power of the Berkeley Rad Lab's cyclotron. I think that I can answer a question about batteries without side discussions of white light sources that are greatly reduced with phosphors or switched supplies.

On Friday, October 2, 2015 at 5:18:48 PM UTC-7, John B. wrote:
On Fri, 2 Oct 2015 15:22:27 -0700 (PDT), wrote:

On Tuesday, September 22, 2015 at 6:54:15 PM UTC-7, John B. wrote:

An interesting statement, given that the Cree XM-L Led, used in many
of the lamps discussed here, "Family Data sheet" shows "Forward
Voltage" ranges from 2.9 VDC to 3.35 VDC at current flows ranging from
700 - 3,000 ma. No mention is made of Forward Voltage as low as 1.5
VDC.

The constant current source probably has a .6 volt or nearly that drop so in order to power the blinky you'll need a power source of about 3.6 volts or a little higher.

John, the Cree XM-L Led is a "white" LED. There is no such thing as a white LED so this is a series/parallel circuit of red/green/yellow or some such. The internal picture appears to show a four LED arrangement that is probably two series networks and a solid state current limiter. This also answers the VERY high 3 amp. current drain. If you want to believe in magic that's up to you.

Four D cell NiCad's would last only two hours or so.

Regardless of how the "white light" is generated, the single Cree XM-L
LED that produces it still has a forward voltage of 2.9 to 3.35 as I
stated.

And, modern "white" LED's are not some sort of multiple circuit
thingamabob. They are a blue LED with a "YAG", phosphor coating.
--
cheers,

John B.

John, there was an interior diagram of that component that showed four separate LED's that appeared to be separate colors. that sort of forward bias indicates two LED's in series. There was a lens covering that did not appear to have a phosphor coating but instead a lens shaped to focus all of the four LED's into a common beam.

Perhaps you're correct since I don't feel like chasing it down again but if you use phosphorus coatings the "white" color isn't very white and the efficiency is pretty low. On battery driven devices efficiency is usually important.

I just did a project for a British company last year in which I used three lead LEDs to achieve red, yellow and green lights as a battery monitor and chopped the supply to limit current. So I am fairly up on battery power to LED lighting.

wrote in message
...
On Friday, October 2, 2015 at 5:18:48 PM UTC-7, John B. wrote:
On Fri, 2 Oct 2015 15:22:27 -0700 (PDT), wrote:

On Tuesday, September 22, 2015 at 6:54:15 PM UTC-7, John B. wrote:

An interesting statement, given that the Cree XM-L Led, used in many
of the lamps discussed here, "Family Data sheet" shows "Forward
Voltage" ranges from 2.9 VDC to 3.35 VDC at current flows ranging from
700 - 3,000 ma. No mention is made of Forward Voltage as low as 1.5
VDC.

The constant current source probably has a .6 volt or nearly that
drop so in order to power the blinky you'll need a power source of
about 3.6 volts or a little higher.

John, the Cree XM-L Led is a "white" LED. There is no such thing as a
white LED so this is a series/parallel circuit of red/green/yellow or
some such. The internal picture appears to show a four LED arrangement
that is probably two series networks and a solid state current limiter.
This also answers the VERY high 3 amp. current drain. If you want to
believe in magic that's up to you.

Four D cell NiCad's would last only two hours or so.

Regardless of how the "white light" is generated, the single Cree XM-L
LED that produces it still has a forward voltage of 2.9 to 3.35 as I
stated.

And, modern "white" LED's are not some sort of multiple circuit
thingamabob. They are a blue LED with a "YAG", phosphor coating.
--
cheers,

John B.

John, there was an interior diagram of that component that showed four
separate LED's that appeared to be separate colors. that sort of forward
bias indicates two LED's in series. There was a lens covering that did not
appear to have a phosphor coating but instead a lens shaped to focus all
of the four LED's into a common beam.

Perhaps you're correct since I don't feel like chasing it down again but
if you use phosphorus coatings the "white" color isn't very white and the
efficiency is pretty low. On battery driven devices efficiency is usually
important.

The early white LEDs were blue with a yellow phosphor, the manufacturers
found that efficiency was better if they used the least phosphor they could
get away with. Unfortunately - this resulted in 'white' LEDs with an
annoying blue tinge.

AFAIK: they've switched to using UV LEDs with white phosphor - current LEDs
seem to be whiter and brighter.

RGB LEDs tend to be used for things like decorative or mood lighting - you
could have a microcontroller varying the RGB mix for a whole range of
changing colours, or maybe mood lighting with a remote handset so you can
adjust the apparent colour temperature.

On Saturday, October 3, 2015 at 4:02:59 PM UTC-4, wrote:

Snipped
I'm sort of confused - you're saying the same thing as I did but quoting spec sheets which most people can't read. Is there some reason for that?


Perhaps because this is a TECHNICAL newsgroup?
Snipped

I spent 40 years building everything from the first heart/lung machine to the automation of PCR to get HIV out of the blood banking system (and then be used to analyze DNA) to increasing the power of the Berkeley Rad Lab's cyclotron. I think that I can answer a question about batteries without side discussions of white light sources that are greatly reduced with phosphors or switched supplies.

Topic drift.

Are you Jeorg or his brother? LOL VBEG

My OP was a question to simply find out if a NiMh battery of the same voltage could be used in place of the supplied Lion battery.

Cheers

On Saturday, October 3, 2015 at 1:36:10 PM UTC-7, Sir Ridesalot wrote:
On Saturday, October 3, 2015 at 4:02:59 PM UTC-4, wrote:

Snipped
I'm sort of confused - you're saying the same thing as I did but quoting spec sheets which most people can't read. Is there some reason for that?


Perhaps because this is a TECHNICAL newsgroup?
Snipped

I spent 40 years building everything from the first heart/lung machine to the automation of PCR to get HIV out of the blood banking system (and then be used to analyze DNA) to increasing the power of the Berkeley Rad Lab's cyclotron. I think that I can answer a question about batteries without side discussions of white light sources that are greatly reduced with phosphors or switched supplies.

Topic drift.

Are you Jeorg or his brother? LOL VBEG

My OP was a question to simply find out if a NiMh battery of the same voltage could be used in place of the supplied Lion battery.

Where do you find an NiMh battery of "the same voltage" as a Li battery? Or is that too technical for you?

On Sat, 3 Oct 2015 13:02:55 -0700 (PDT), wrote:

On Friday, October 2, 2015 at 4:47:55 PM UTC-7, Jeff Liebermann wrote:

If you don't care about efficiency, a linear current source is good
and cheap. However, if you want your light to have a constant light
output (until the battery quits) and for your battery to last, one of
several types of switchers work better with the added bonus of
brightness control.

Both phosphorus and switched supplies reduces the brilliance of the light.

Brilliance? What units of measure does one use to measure brilliance?
Luminous flux is measured in lumens. Light intensity is measured in
lux or ft-candles. Brilliance is possibly proportional to one's IQ or
the cut of a diamond.

Also, your one liner doesn't quite make sense. If I use a switching
power supply, linear power supply, battery, or dynamo, the power
source will produce exactly the same light intensity for the same
power supply voltage. Could your rephrase your statement so that it
makes sense? Were you perhaps referring to luminous efficacy
(lumens/watt)?
https://en.wikipedia.org/wiki/Luminous_efficacy

The Cree XM-L LED typically runs at 1.5 to 2.0A average current. At
0.6v drop in your current source, that's 0.9 to 1.2 watts in heat.
That's not a huge amount, but it's still wasted power.

I'm sort of confused - you're saying the same thing as I did but
quoting spec sheets which most people can't read. Is there some
reason for that?

Well, since you trimmed what you were saying from your reply, it's
rather awkward to determine if I'm saying the same thing. I believe
this is your message, which seems to lack any references to the LED
data sheet, or mention of heat wasted in a linear current regulator.
https://groups.google.com/forum/#!original/rec.bicycles.tech/ajDhrejRYuE/auYaO2jKAgAJ
I don't believe I said the same thing as anything in your posting.

Also, I post URL's to substantiate my claims, and to provide reference
material for anyone that is interested in pursuing the topic. If you
are experiencing difficulties understanding an LED data sheet, I would
gladly answer any questions you might have. Also note that there are
several engineers that post regularly to rec.bicycles.tech, that are
also very knowledgeable on topic of bicycle lighting.

The question was whether there was a cheaper replacement for the
Lithium Ion battery and a quick off-the-cuff reply was YES there is.

I call to your attention the Subject field of this thread:
"Can replace Lithium with Nimh external battery pack?"
Please note the mention of a NiMH battery and the lack of interest in
an NiCd substitution.

If you want to argue spec sheet figures to three decimal places
doesn't that ignore the question? Do you wish to discuss recharging
rates and their effects on battery life? Is that any more to the
point?

True. It does ignore the original question, which you also seem to be
doing. My calculations were also to two decimal places, not three. If
you wish to change the topic, I think it would be better if you would
start a new thread. Please note that the specifications for the Cree
XM-L series LED's were introduced to provide a realistic example of
what the battery would be expected to power.

I spent 40 years building everything from the first heart/lung
machine to the automation of PCR to get HIV out of the blood banking
system (and then be used to analyze DNA) to increasing the power
of the Berkeley Rad Lab's cyclotron. I think that I can answer
a question about batteries without side discussions of white light
sources that are greatly reduced with phosphors or switched supplies.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

wrote in message
...
On Saturday, October 3, 2015 at 1:36:10 PM UTC-7, Sir Ridesalot wrote:
On Saturday, October 3, 2015 at 4:02:59 PM UTC-4,
wrote:

Snipped
I'm sort of confused - you're saying the same thing as I did but
quoting spec sheets which most people can't read. Is there some reason
for that?


Perhaps because this is a TECHNICAL newsgroup?
Snipped

I spent 40 years building everything from the first heart/lung machine
to the automation of PCR to get HIV out of the blood banking system
(and then be used to analyze DNA) to increasing the power of the
Berkeley Rad Lab's cyclotron. I think that I can answer a question
about batteries without side discussions of white light sources that
are greatly reduced with phosphors or switched supplies.

Topic drift.

Are you Jeorg or his brother? LOL VBEG

My OP was a question to simply find out if a NiMh battery of the same
voltage could be used in place of the supplied Lion battery.

Where do you find an NiMh battery of "the same voltage" as a Li battery?
Or is that too technical for you?

With 1.2V nominal, 3 in series is pretty much the same as the nominal for a
lithium cell.

If the current controlling device can handle it, I'd go for 4 cells and
4.8V. With a switch-mode current controller it would take longer to reach
the drop out voltage - if its just a resistive dropper, the extra voltage
will just waste power.

The current crop of AA Ni-Mh cells are around the 2300mAh mark, the larger
18650 lithium cell can be anywhere from 2200mAh to about 2800mAh. When you
take into account the larger 18650 against the bulk of 3x AA, there isn't a
lot in it, but lithium takes a small lead.

A big problem with Ni-Mh is their internal resistance - they get hot if you
draw much current. Ni-Cd is size for size comparable to lead acid in peak
current capability, but the Ah capacity is typically 1/4 that of Ni-Mh.

On Sunday, October 4, 2015 at 8:49:41 AM UTC-7, Ian Field wrote:
wrote in message

Where do you find an NiMh battery of "the same voltage" as a Li battery?
Or is that too technical for you?

With 1.2V nominal, 3 in series is pretty much the same as the nominal for a
lithium cell.

If the current controlling device can handle it, I'd go for 4 cells and
4.8V. With a switch-mode current controller it would take longer to reach
the drop out voltage - if its just a resistive dropper, the extra voltage
will just waste power.

The current crop of AA Ni-Mh cells are around the 2300mAh mark, the larger
18650 lithium cell can be anywhere from 2200mAh to about 2800mAh. When you
take into account the larger 18650 against the bulk of 3x AA, there isn't a
lot in it, but lithium takes a small lead.

A big problem with Ni-Mh is their internal resistance - they get hot if you
draw much current. Ni-Cd is size for size comparable to lead acid in peak
current capability, but the Ah capacity is typically 1/4 that of Ni-Mh.

And you have done nothing more than repeat me.

As for the heat problem - since our first poster was looking for long life I was suggesting C or D cells which can supply a lot of current with minimal heating. Also most available chargers would be low current chargers for such a setup and so you wouldn't have to worry about overheating on recharge..

On Saturday, October 3, 2015 at 10:53:06 PM UTC-7, Jeff Liebermann wrote:
On Sat, 3 Oct 2015 13:02:55 -0700 (PDT), wrote:

Both phosphorus and switched supplies reduces the brilliance of the light.

wrote in message
...
On Sunday, October 4, 2015 at 8:49:41 AM UTC-7, Ian Field wrote:
wrote in message

Where do you find an NiMh battery of "the same voltage" as a Li
battery?
Or is that too technical for you?

With 1.2V nominal, 3 in series is pretty much the same as the nominal for
a
lithium cell.

If the current controlling device can handle it, I'd go for 4 cells and
4.8V. With a switch-mode current controller it would take longer to reach
the drop out voltage - if its just a resistive dropper, the extra voltage
will just waste power.

The current crop of AA Ni-Mh cells are around the 2300mAh mark, the
larger
18650 lithium cell can be anywhere from 2200mAh to about 2800mAh. When
you
take into account the larger 18650 against the bulk of 3x AA, there isn't
a
lot in it, but lithium takes a small lead.

A big problem with Ni-Mh is their internal resistance - they get hot if
you
draw much current. Ni-Cd is size for size comparable to lead acid in peak
current capability, but the Ah capacity is typically 1/4 that of Ni-Mh.

And you have done nothing more than repeat me.

As for the heat problem - since our first poster was looking for long life
I was suggesting C or D cells which can supply a lot of current with
minimal heating. Also most available chargers would be low current
chargers for such a setup and so you wouldn't have to worry about
overheating on recharge.


AFAIK: the nickel chemistry cells are endothermic during charging - it takes
some *SERIOUS* brute force and ignorance fast charging to make them heat up
before the fully charged point.