Can replace Lthium with Nimh external battery pack?

YO SR how's the new batts goin'

SR ?


http://goo.gl/xQ7BhD

On Tue, 22 Sep 2015 13:12:35 -0700 (PDT), wrote:

On Tuesday, September 22, 2015 at 11:21:48 AM UTC-7, Sir Ridesalot wrote:
On Tuesday, September 22, 2015 at 12:56:34 PM UTC-4, Jeff Liebermann wrote:
On Mon, 21 Sep 2015 23:24:25 -0700 (PDT), Sir Ridesalot
wrote:

I have the NiMh charger too. If I did get the Lion powered
light it'd come with Lion battery charger. thus there's
no concern about using the wrong charger on the battery pack.

I guess this is for one of the Cygolite LiIon lights that you were
considering purchasing. (Sorry, I missed the previous thread on the
topic). Cygolite seems to standardize on a 7.6v DC LiIon battery pack
for the lights. No NiMH packs available.
http://www.shop.cygolite.com/category.sc?categoryId=24

7.6 VDC would be two 3.8 VDC LiIon cells. To produce that using NiMH
cells would requi
7.6 / 1.35 = 5.6 cells
which isn't going to work. The best I can do is 6 cells, for:
1.35 * 6 = 8.1 VDC
which requires a voltage drop of:
8.1 - 7.6 = 0.5 VDC
which can easily be accomplished with a single power diode in series
with the battery pack. I don't like the power loss in the diode, but
it should work. The diode should be built into a plug and jack power
adapter installed between the NiMH pack and the light. That way, you
can use the NiMH charger, without the diode getting in the way. That
will also allow you to use a LiIon pack, but simply removing the diode
adapter.

Permit me to offer an alternative approach. Instead of reverting to
NiMH cells, just find a cheaper LiIon battery pack. I suggest you
look at the various radio control batteries. What you want are the
biggest LiIon batteries possible in a 2S pack (possibly with the
balance charger connector). 2S packs sorted by price:
http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?cwhl=XX&idCategor y=86&v=&sortlist=P&LiPoConfig=2&CatSortOrder=desc
I can't calculate how many milliamp-hrs will be needed without knowing
which light you plan to use. After that, it's packaging (stuff it in
a water bottle) and adapters for the power connector.

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

Thanks Jeff. I guess I'll stick with Lion packs for whatever Cygolite i get. BTW, all my NiMh batteries for my RC boats are 7.2 volts according to the battery info on the battery.

cheers

LED's require about 1.5V per light. Since the Lion puts out over 3 volts the usual circuit is to use a low voltage controller driving a constant current source and powering the LED's two in a serial configuration.


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.

So you could drive it with three NiMH batteries in series and any number of those set ups in parallel to supply the expected lifespan before requiring a charge.

You can recharge them via a normal NiMH recharger by taking the cells out of the battery box and inserting them individually into the charger. There are high speed smart chargers all over the Internet including Amazon and Ebay.

Lights are not rocket science.
--
cheers,

John B.

wrote in message
...
On Tuesday, September 22, 2015 at 11:21:48 AM UTC-7, Sir Ridesalot wrote:
On Tuesday, September 22, 2015 at 12:56:34 PM UTC-4, Jeff Liebermann
wrote:
On Mon, 21 Sep 2015 23:24:25 -0700 (PDT), Sir Ridesalot
wrote:

I have the NiMh charger too. If I did get the Lion powered
light it'd come with Lion battery charger. thus there's
no concern about using the wrong charger on the battery pack.

I guess this is for one of the Cygolite LiIon lights that you were
considering purchasing. (Sorry, I missed the previous thread on the
topic). Cygolite seems to standardize on a 7.6v DC LiIon battery pack
for the lights. No NiMH packs available.
http://www.shop.cygolite.com/category.sc?categoryId=24

7.6 VDC would be two 3.8 VDC LiIon cells. To produce that using NiMH
cells would requi
7.6 / 1.35 = 5.6 cells
which isn't going to work. The best I can do is 6 cells, for:
1.35 * 6 = 8.1 VDC
which requires a voltage drop of:
8.1 - 7.6 = 0.5 VDC
which can easily be accomplished with a single power diode in series
with the battery pack. I don't like the power loss in the diode, but
it should work. The diode should be built into a plug and jack power
adapter installed between the NiMH pack and the light. That way, you
can use the NiMH charger, without the diode getting in the way. That
will also allow you to use a LiIon pack, but simply removing the diode
adapter.

Permit me to offer an alternative approach. Instead of reverting to
NiMH cells, just find a cheaper LiIon battery pack. I suggest you
look at the various radio control batteries. What you want are the
biggest LiIon batteries possible in a 2S pack (possibly with the
balance charger connector). 2S packs sorted by price:
http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?cwhl=XX&idCategor y=86&v=&sortlist=P&LiPoConfig=2&CatSortOrder=desc
I can't calculate how many milliamp-hrs will be needed without knowing
which light you plan to use. After that, it's packaging (stuff it in
a water bottle) and adapters for the power connector.

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

Thanks Jeff. I guess I'll stick with Lion packs for whatever Cygolite i
get. BTW, all my NiMh batteries for my RC boats are 7.2 volts according
to the battery info on the battery.

cheers

LED's require about 1.5V per light. Since the Lion puts out over 3 volts
the usual circuit is to use a low voltage controller driving a constant
current source and powering the LED's two in a serial configuration.

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.

So you could drive it with three NiMH batteries in series and any number
of those set ups in parallel to supply the expected lifespan before
requiring a charge.

You can recharge them via a normal NiMH recharger by taking the cells out
of the battery box and inserting them individually into the charger. There
are high speed smart chargers all over the Internet including Amazon and
Ebay.

Lights are not rocket science.

Batteries are though - they found out to their cost about Ni-Cd memory
effect on cells that never fully discharged but were periodically topped up
by the solar panels on the satellite.

Lithium cells are capable of supplying very high peak current draw - Ni-Mh
aren't. They have high internal resistance that will waste energy heating
the battery instead of lighting the load. In the past I tried putting Ni-Mh
celles in a rechargeable shaver that originally had Ni-Cd, the running time
was no more than with the knackered cells I took out - despite the Ni-Mh
cells having nearly 4x the rated Ah capacity.

Ni-Cd cells are not far behind lithium on peak current capability, but
typical Ah capacity is about 1/4 of the latest Ni-Mh cells. Its not easy to
make a direct comparison with lithium because there's so few common cell
sizes.

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.

On 10/2/2015 6:22 PM, wrote:

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.

Well, that's possible, I suppose. But I think it's more common to get
white light by using a blue LED and a phosphor lens to convert the
result to white.

See http://www.lrc.rpi.edu/programs/nlpi...whiteLight.asp

and http://www.popsci.com/article/techno...th-nobel-prize

--
- Frank Krygowski

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.

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.

Wrong. The white LED's used in all cycling lamps which I've seen use
a blue or UV LED exciting some phosphor to produce the white light.
http://energy.gov/eere/ssl/led-basics
https://en.wikipedia.org/wiki/Light-emitting_diode#Phosphor-based_LEDs
There are some that use RGB LED's to produce various colors. However,
the white light these produce is visibly different from the
blue-yellow spectra produced by white phosphor LED.

The internal picture appears to show a four LED arrangement
that is probably two series networks and a solid state current limiter.

What internal picture? URL please. Is it the CREE XM-L data sheet,
which shows no such arrangement?
http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/xlamp-xml
http://www.cree.com/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XLampXML.pdf

This also answers the VERY high 3 amp. current drain.

I wasn't aware that there was a question about the "high" current. If
that's the answer, what's the question?

If you want to believe in magic that's up to you.

I believe and practice magic. RF (radio frequency) design is well
known to be based on magic.

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

The original question was about replacing a LiIon battery pack with an
existing NiMH battery pack, not a NiCd.


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

On Tue, 22 Sep 2015 13:12:35 -0700 (PDT), wrote:

LED's require about 1.5V per light.

White LED's vary from 2.6 to 3.3VDC. See Electrical Characteristics
graph for the common Cree XM-L series:
http://www.cree.com/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XLampXML.pdf

Since the Lion puts out over 3 volts the usual circuit is to use a
low voltage controller driving a constant current source and
powering the LED's two in a serial configuration.

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.

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.

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.

So you could drive it with three NiMH batteries in series and any
number of those set ups in parallel to supply the expected lifespan
before requiring a charge.

Well, according to my measurements at 2A drain, a commodity NiMH
battery spends much of its life running at 1.1VDC.
http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg
Three of those would give you 3.3VDC, which will run a Cree XM-L LED
with a voltage drop varying from 0 to 0.7VDC. You can't easily do
that with any linear xisistor or resistor device. Well, maybe a PTC
thermistor but that's also a power burner. You'll need one more NiMH
cell to make your linear regulator work. (Hint: Don't use typical
specs for batteries. Use the specs at the operating currents).

You can recharge them via a normal NiMH recharger by taking the
cells out of the battery box and inserting them individually into
the charger. There are high speed smart chargers all over the
Internet including Amazon and Ebay.

Yeah, except that if you use a really good NiMH cell, such as
Sanyo/Panasonic Eneloop cells, they won't take a quick charge. I know
because I managed to kill 4 AA cells with a Maha quick charger. The
real trick is to either read the fine print, or be smarter than the
smart charger.

Lights are not rocket science.

Actually, they are quite complex if you consider all the parameters
that must be optimized and compromised. Efficiency, brightness,
dimming, pattern, battery runtime, battery life (charge cycles),
ambient temperature, dissipation, thermal management, control, stand
lighting, dynamo/battery power, charge time, replaceable batteries,
reverse idiot battery protection, etc. Anyone can make a light that
works in the lab running on a bench power supply. The same light in
the real world is quite different.

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

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.

On Sat, 3 Oct 2015 17:45:43 +0100, "Ian Field"
wrote:

The other way of doing it is with an RGB LED module. Having 3 LED chips in
the package makes them more expensive, and each LED chip has a different
forward voltage drop and efficiency figure as related to current. It usually
takes a bit of control to balance the red, green and blue to make the tone
of white just right.

And no matter how you do it, tetrachromats, dichromats, and anomolopes
are going to complain.

--
joy beeson at comcast dot net
http://wlweather.net/PAGEJOY/
The above message is a Usenet post.
I don't recall having given anyone permission to use it on a Web site.

wrote in message
...
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.

The actual LED can be blue or UV, the blue ones have a yellow phosphor and
the UV ones have a white phosphor.

The other way of doing it is with an RGB LED module. Having 3 LED chips in
the package makes them more expensive, and each LED chip has a different
forward voltage drop and efficiency figure as related to current. It usually
takes a bit of control to balance the red, green and blue to make the tone
of white just right.