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using rechargable batteries on the bike



 
 
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  #1  
Old December 22nd 04, 01:17 AM
Dave Croft
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Default using rechargable batteries on the bike

I have a number of new 3000 mah 1.2 volt rechargeable batteries
to use for lighting on the bike.
What is the recommended bulb voltage & amperage especially
to get a good beam on the headlight.
I suspect somewhere around 2.0 to 2.2 volt but I cannot find
anyone selling bulbs like this in the UK.
TIA
--
Dave Croft
Warrington
England


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  #2  
Old December 22nd 04, 01:59 AM
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Dave Croft wrote:

I suspect somewhere around 2.0 to 2.2 volt but I cannot find
anyone selling bulbs like this in the UK.


And you never will.

Hook six of these batteries in series to get 7.2V. Over-voltage a 6V
MR16 bulb by 20%.

See "http://www.e-go.gb.com/parts.asp" to obtain a 6 volt/5 watt MR16
lamp.

I haven't seen MR16 6 volt lamps, at more than 5 watts, except
integrated into some emergency lights, and these don't have a front
glass attached, see
"http://www.cooperlighting.com/specfiles/productinfopdf/EADX0497.pdf".
Steve
http://bicyclelighting.com

  #3  
Old December 22nd 04, 04:48 AM
Sheldon Brown
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Quoth Dave Croft:

I have a number of new 3000 mah 1.2 volt rechargeable batteries
to use for lighting on the bike.
What is the recommended bulb voltage & amperage especially
to get a good beam on the headlight.
I suspect somewhere around 2.0 to 2.2 volt but I cannot find
anyone selling bulbs like this in the UK.


Most bicycle lights run on 6 volts. 5 of your 1.2 volt cells in series
(head to tail) would give you that.

Many 6-volt bike lights are set up to run on 4 1.5 volt cells, typical
voltage for disposable cells. If you run 1.2 volt rechargeables, you
only get 4.8 volts, but in practice this tends to work OK too.

Sheldon "Sparks" Brown
Newtonville, Massachusetts
+------------------------------------------+
| Genius is one per cent inspiration and |
| ninety-nine per cent perspiration. |
|. --Thomas Edison |
+------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

  #4  
Old December 22nd 04, 05:06 AM
Tom Sherman
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Sheldon Brown wrote:

...
Many 6-volt bike lights are set up to run on 4 1.5 volt cells, typical
voltage for disposable cells....


The actual voltage will depend on the resistance of the circuit and the
internal resistance of the cell. A standard alkaline-manganese battery
will have an open circuit voltage (when new) ranging from about 1.58 to
1.61 volts {1]. Voltage will drop to the range of 1.5 to 1.3 volts for
devices intended for use with such batteries.

While the open circuit voltage of a NiCad or NiMH cell will be lower,
these cells have a much lower internal resistance than the alkaline
cell, therefore their voltage will not drop as much into a low
resistance load, such a halogen bulb.

[1] At least this is true for the thousands of commercially produced
LR-03 (AAA), LR-6 (AA), LR-15 (C) and LR-20 (D) alkaline-manganese cells
I have measured.

--
Tom Sherman

  #5  
Old December 22nd 04, 05:50 AM
Weisse Luft
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Most rechargeable batteries have much lower internal resistance than
comparable disposable types. Lower internal resistance means less
voltage depression under load. A 6V nominal alkaline pack might drop
to 5.5 V under a 1 amp load where a NiCd will only drop to 5.4 V. NiCd
are rated at 1.2 V nominal per cell but in actuality, this is the median
voltage over the entire charge. Full charge is 1.4 V and completely
empty is 1.0, both measured under load. Alkaline cells are only 1.5 V
per cell at full charge but drop to about 1.35 at near total discharge.


--
Weisse Luft

  #6  
Old December 22nd 04, 05:56 AM
Matt O'Toole
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Sheldon Brown wrote:

Most bicycle lights run on 6 volts. 5 of your 1.2 volt cells in
series (head to tail) would give you that.

Many 6-volt bike lights are set up to run on 4 1.5 volt cells, typical
voltage for disposable cells. If you run 1.2 volt rechargeables, you
only get 4.8 volts, but in practice this tends to work OK too.


The reason it works is that 4 alkaline cells, rated at a nominal 1.5V each,
deliver less than 6V under the heavy, multi-watt load of a bike light. With
this in mind, these lights use lower voltage bulbs to begin with, which are a
good match for 1.2V rechargeables.

Matt O.


  #7  
Old December 22nd 04, 12:29 PM
Pete Biggs
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Dave Croft wrote:
I have a number of new 3000 mah 1.2 volt rechargeable batteries
to use for lighting on the bike.
What is the recommended bulb voltage & amperage especially
to get a good beam on the headlight.
I suspect somewhere around 2.0 to 2.2 volt but I cannot find
anyone selling bulbs like this in the UK.


A 2.4 volt Krypton bulb* powered by 2 x 1.2 volt NiCad or NiMH 'C' cells
will produce enough light to be seen by (brighter & whiter than 2 x 1.5
volt alkalines), but barely enough of a beam to see by.

An LED lamp would be more useful if battery power is limited as they are
much more effecient.

* Available cheaply in the UK from shops like Wilkinsons.

MR11 & MR16 bulbs:
www.ricam.co.uk
www.gbbulbs.co.uk
www.lumicycle.co.uk (5 & 12W MR11 spots)

~PB


  #8  
Old December 22nd 04, 04:24 PM
Steven M. Scharf
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Pete Biggs wrote:

An LED lamp would be more useful if battery power is limited as they are
much more effecient.


They are much less efficient in terms of the power required to produce
an identical beam.

  #9  
Old December 22nd 04, 06:13 PM
Sheldon Brown
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Default

I wrote:

Most bicycle lights run on 6 volts. 5 of your 1.2 volt cells in
series (head to tail) would give you that.

Many 6-volt bike lights are set up to run on 4 1.5 volt cells, typical
voltage for disposable cells. If you run 1.2 volt rechargeables, you
only get 4.8 volts, but in practice this tends to work OK too.


Matt O'Toole wrote:

The reason it works is that 4 alkaline cells, rated at a nominal 1.5V each,
deliver less than 6V under the heavy, multi-watt load of a bike light. With
this in mind, these lights use lower voltage bulbs to begin with, which are a
good match for 1.2V rechargeables.


Yes, I know that, but it wasn't relevant to the OP's question, and I
didn't want to confuse him or or her with extraneous details.

Sheldon "Simplicity" Brown
+-----------------------------------------------------------+
| Sometimes the only thing more dangerous than a question |
| is an answer. --Ferengi Rule of Acquisition #208 |
+-----------------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

  #10  
Old December 22nd 04, 10:56 PM
Andrew Webster
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Steven M. Scharf wrote:
Pete Biggs wrote:

An LED lamp would be more useful if battery power is limited as they are


much more effecient.



They are much less efficient in terms of the power required to produce
an identical beam.

See

http://nordicgroup.us/s78/wattslumens.html

Where data is presented to show that LEDs can be more efficient than
incandescent lamps (though perhaps not by as much as some might think).

In practice I have changed from a 6W halogen bulb to a 1W Everled
replacement bulb. With the same 5xAA NiMH power source I am now getting
about 6 hours run time instead of 1.5 hours, the same or better
illumination.

Bike lights will always be a compromise between power, weight and
run-time. LEDs can certainly help increase run-time.

As ever, a bright light is one thing, but getting the light in the right
place is another. It is a much discussed point that mounting lights in
a sensible place and using an appropriate beam can make much better use
of the light available.

Andrew Webster
 




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