DIY bike lights / AA battery current

I'm thinking of making a DIY halogen bike light, I've seen a few web
pages on them and it looks like they're neither difficult nor expensive
to make, the biggest cost is the battery and recharger.

Places like Dick Smith sell 12V halogen globes for just a few bucks,
and I'm considering a 20W light system. I've got a very old cheap
incandescent bike light which I can put a bright bulb into and run
wires out to an external battery pack hanging from my top tube or
handlebar stem.

Battery options include sealed lead acid units and ligher, but more
expensive, NiMH packs.

Another option would be a bank of 10 rechargeable NiMH AA batteries in
series. This would provide the right voltage, but I'm wondering if
they could provide sufficient current (I'm aware of issues of internal
resistance etc) and would they be able to keep up the current for at
least an hour (my commute time).

First of all, would 10 NiMH batteries in series be capable of providing
a 1.7 amp current, and if so for how long?

If not, what are some suggested alternative batteries and chargers that
would fit the bill?

I could run two packs of 10, in parallel, which would provide the same
voltage but double the current, though 20 NiMh batteries would be
pretty costly and a sealed lead acid battery might be better and
cheaper anyway.

I don't do night races or offroad stuff, its just to provide a nice
wall of light for my winter night commutes.

Thanks in advance

Travis

First of all, would 10 NiMH batteries in series be capable of providing
a 1.7 amp current, and if so for how long?

From my experiance (I tried this using jaycar bulbs and AAs from ebay),
no. The '2400mah' AAs really don't like being worked that hard and
neither voltage or capacity live up to what they should. Theoritical
run time would be 1.4 hours, but I'd say you'd be looking at barely an
hour. You also wouldn't get anything like 20W out of the bulb.

What I would recommend you do instead is run a 10W bulb from 12 AA
batteries. This combats the voltage sag, and you end up with a mildly
overvolted bulb. Battery life would be between 2 and 2.5 hours, and due
to the magic of overvolting (http://www.myra-simon.com/bike/lights.html)
you'd have at least as much light as the 20W from 10 AAs example above.
The downside is significantly reduced bulb life, but by significantly
reduced we are talking hundreds instead of thousands of hours. When
bulbs cost about five bucks, I figure that's not much of a sacrifice.

Now if you wanted a light for night offroading, I'd suggest you get a
12v 4800mah Li-ion battery from batteryspace.com and run the 20W bulb
from that. That's my MTB light set up, and it's bloody awesome (if
expensive). Rivals my friends' HID lights. Batteryspace is also useful
if you want to get a prebuilt nimh battery pack rather than building
your own.


--
SomeGuy

On 2006-04-22, Travis (aka Bruce)
was almost, but not quite, entirely unlike tea:
First of all, would 10 NiMH batteries in series be capable of providing
a 1.7 amp current, and if so for how long?

1.7amps shouldn't be a problem. AAs seem to be rated about 2200mAH
these days, so at 1A, with the internal resistance, I would expect it
would last for almost precisely an hour.

Be noted though, that the initial voltage (maybe for 5/10 minutes?)
will be somewhere around 14 or 15 volts. Hmmm, a bit high?

I could run two packs of 10, in parallel, which would provide the same
voltage but double the current, though 20 NiMh batteries would be
pretty costly and a sealed lead acid battery might be better and
cheaper anyway.

NiMH and NiCd are always going to be much more expensive than SLA,
depends whether you want the weight saving or not. Oh, and the
longevity, as long as you use a good charger.

--
TimC
Animals who are not penguins can only wish they were.

"Travis"

I'm thinking of making a DIY halogen bike light, I've seen a few web
pages on them and it looks like they're neither difficult nor expensive
to make, the biggest cost is the battery and recharger.

Places like Dick Smith sell 12V halogen globes for just a few bucks,
and I'm considering a 20W light system.


** That would be very bright and a point sized source.

Maybe dazzling to a motorist ?


I've got a very old cheap
incandescent bike light which I can put a bright bulb into and run
wires out to an external battery pack hanging from my top tube or
handlebar stem.

Battery options include sealed lead acid units and ligher, but more
expensive, NiMH packs.

Another option would be a bank of 10 rechargeable NiMH AA batteries in
series. This would provide the right voltage, but I'm wondering if
they could provide sufficient current (I'm aware of issues of internal
resistance etc) and would they be able to keep up the current for at
least an hour (my commute time).

First of all, would 10 NiMH batteries in series be capable of providing
a 1.7 amp current, and if so for how long?


** Good quality AA NiMH cells have a 1.7 hour run time at 1 amp.

Should be able to do 1.7 amps for 1 hour.

2.1 amp/hour capacity and more are available.


I don't do night races or offroad stuff, its just to provide a nice
wall of light for my winter night commutes.


** A *long time* ago I had the same idea - used a 6 volt, 10 watt "sealed
beam" GE lamp powered by 5 x WW2 vintage NiFe cells. Similar light output
to an average motorbike headlamp using bulb and reflector.

Good for about a 45minute ride.



....... Phil

On Fri, 21 Apr 2006 21:31:09 -0700, Travis wrote:


Another option would be a bank of 10 rechargeable NiMH AA batteries in
series. This would provide the right voltage, but I'm wondering if
they could provide sufficient current (I'm aware of issues of internal
resistance etc) and would they be able to keep up the current for at
least an hour (my commute time).

Technically it provides the right voltage. In practice the batteries can't
provide that voltage at the desired current, and you get a dull light.
This can be offset by increasing voltage - 12 AAs should give a bright
light. However, you'll be doing well to get an hour out of a set.

You can get AAs to run 10W stuff OK, but 20 is just a tad too much.

If not, what are some suggested alternative batteries and chargers that
would fit the bill?

Sub Cs can be got for $5 each if you look around. There's a mob in
Brisbane who do mail order - I think I found them on ebay, but can't
remember their name. That's for 3.5Ah, which will handle the current OK,
and give you a solid 2 hours of light. To go more than that you'll need a
bigarse SLA or a bigarse budget.

I don't do night races or offroad stuff, its just to provide a nice wall
of light for my winter night commutes.

If you're doing home made commuter lights, get a 3W Luxeon ($20) and
either a prebuilt regulator or get the el cheapo one from
http://www.oatleyelectronics.com which only involves a bit of soldering. A
collimating lens and a heatsink and you should have something that runs
nicely for a couple of hours off 5 AAs (use 6V, it's possible to use 4.8
(4cells ) but it's a bugger to get the regulator working well).

http://www.hired-goons.net/lights has some more info, though is wildly out
of date.

--
Dave Hughes |
Striker, listen, and you listen close: flying a plane is no different
than riding a bicycle just a lot harder to put baseball cards in the
spokes.

On Sat, 22 Apr 2006 05:03:35 +0000, TimC wrote:

1.7amps shouldn't be a problem. AAs seem to be rated about 2200mAH
these days, so at 1A, with the internal resistance, I would expect it
would last for almost precisely an hour.

As I said in my earlier post, but want to reinforce - you'll get serious
voltage sag. I forgot to mention that cheap battery holders can't handle
this type of current. I tried it and was losing around 0.5V per
connection. I wondered why a lamp being run from 12 AAs was barely
lighting up. Best option is to get tabbed cells and solder them up, but
that makes charging trickier. If you know what you're doing you can gin up
better contacts in the battery holder, but it's not that simple an
exercise.

NiMH and NiCd are always going to be much more expensive than SLA,
depends whether you want the weight saving or not. Oh, and the
longevity, as long as you use a good charger.

NiMH is actually pretty good value in AAs these days. Ebay and the huge
demand for AAs in consumer devices means you can get ~2Ah cells for around
$2.50-$3 each.

--
Dave Hughes |
"Did you know God had a plan for you?"
"Does it involve a high-powered rifle and a belltower?"

The last two Silicon Chip magazines www.siliconchip.com.au have featured a
circuit to drive up to 6W of Luxeon LED's. The circuit is based around a
microcontroller chip and a switchmode power supply that keeps up the current
to the LEDS as the batteries run down. It also controls the recharging so a
laptop power supply or any approx 12v 700ma supply will be a suitable
charger. They feature a 5W LED example on a bike and it looks really bright.
They made the claim that it is bright enough to safely travel at 75kph,
downhill of course.

It has a number of functions but the bicycle headlight version has a light
sensor so that it flashes at 4 hertz
when it isn't dark enough to need a full on headlight.

The preprogrammed microcontroller chip is available from Silicon Chip for
$25 but you'd need to source the other parts like Circuit board.

Even if you don't build it it might give some ideas. Try www.jaycar.com.au
for stores where last months issue might still be available.Dick smith
stores might sell Silicon Chip also.
Regards Wilfred

"Random Data" wrote in message
news
On Fri, 21 Apr 2006 21:31:09 -0700, Travis wrote:


Another option would be a bank of 10 rechargeable NiMH AA batteries in
series. This would provide the right voltage, but I'm wondering if
they could provide sufficient current (I'm aware of issues of internal
resistance etc) and would they be able to keep up the current for at
least an hour (my commute time).

Technically it provides the right voltage. In practice the batteries can't
provide that voltage at the desired current, and you get a dull light.
This can be offset by increasing voltage - 12 AAs should give a bright
light. However, you'll be doing well to get an hour out of a set.

You can get AAs to run 10W stuff OK, but 20 is just a tad too much.

If not, what are some suggested alternative batteries and chargers that
would fit the bill?

Sub Cs can be got for $5 each if you look around. There's a mob in
Brisbane who do mail order - I think I found them on ebay, but can't
remember their name. That's for 3.5Ah, which will handle the current OK,
and give you a solid 2 hours of light. To go more than that you'll need a
bigarse SLA or a bigarse budget.

I don't do night races or offroad stuff, its just to provide a nice wall
of light for my winter night commutes.

If you're doing home made commuter lights, get a 3W Luxeon ($20) and
either a prebuilt regulator or get the el cheapo one from
http://www.oatleyelectronics.com which only involves a bit of soldering. A
collimating lens and a heatsink and you should have something that runs
nicely for a couple of hours off 5 AAs (use 6V, it's possible to use 4.8
(4cells ) but it's a bugger to get the regulator working well).

http://www.hired-goons.net/lights has some more info, though is wildly out
of date.

--
Dave Hughes |
Striker, listen, and you listen close: flying a plane is no different
than riding a bicycle just a lot harder to put baseball cards in the
spokes.

the 20w qh globe will exceed any led brightness and be a lot cheaper

12v 7AH SLH battery is cheaper and has less volt drop at heavy loads
than the equiv 30x AA 2200 mAH cells and no heavier

you don't need a microcontroller or any other useless crap, just a
battery wires and a switch



"Wilfred Kazoks" wrote in message
...
: The last two Silicon Chip magazines www.siliconchip.com.au have
featured a
: circuit to drive up to 6W of Luxeon LED's. The circuit is based around
a
: microcontroller chip and a switchmode power supply that keeps up the
current
: to the LEDS as the batteries run down. It also controls the recharging
so a
: laptop power supply or any approx 12v 700ma supply will be a suitable
: charger. They feature a 5W LED example on a bike and it looks really
bright.
: They made the claim that it is bright enough to safely travel at
75kph,
: downhill of course.
:
: It has a number of functions but the bicycle headlight version has a
light
: sensor so that it flashes at 4 hertz
: when it isn't dark enough to need a full on headlight.
:
: The preprogrammed microcontroller chip is available from Silicon Chip
for
: $25 but you'd need to source the other parts like Circuit board.
:
: Even if you don't build it it might give some ideas. Try
www.jaycar.com.au
: for stores where last months issue might still be available.Dick smith
: stores might sell Silicon Chip also.
: Regards Wilfred
:
: "Random Data" wrote in message
: news : On Fri, 21 Apr 2006 21:31:09 -0700, Travis wrote:
:
:
: Another option would be a bank of 10 rechargeable NiMH AA batteries
in
: series. This would provide the right voltage, but I'm wondering if
: they could provide sufficient current (I'm aware of issues of
internal
: resistance etc) and would they be able to keep up the current for
at
: least an hour (my commute time).
:
: Technically it provides the right voltage. In practice the batteries
can't
: provide that voltage at the desired current, and you get a dull
light.
: This can be offset by increasing voltage - 12 AAs should give a
bright
: light. However, you'll be doing well to get an hour out of a set.
:
: You can get AAs to run 10W stuff OK, but 20 is just a tad too much.
:
: If not, what are some suggested alternative batteries and chargers
that
: would fit the bill?
:
: Sub Cs can be got for $5 each if you look around. There's a mob in
: Brisbane who do mail order - I think I found them on ebay, but can't
: remember their name. That's for 3.5Ah, which will handle the
current OK,
: and give you a solid 2 hours of light. To go more than that you'll
need a
: bigarse SLA or a bigarse budget.
:
: I don't do night races or offroad stuff, its just to provide a nice
wall
: of light for my winter night commutes.
:
: If you're doing home made commuter lights, get a 3W Luxeon ($20) and
: either a prebuilt regulator or get the el cheapo one from
: http://www.oatleyelectronics.com which only involves a bit of
soldering. A
: collimating lens and a heatsink and you should have something that
runs
: nicely for a couple of hours off 5 AAs (use 6V, it's possible to use
4.8
: (4cells ) but it's a bugger to get the regulator working well).
:
: http://www.hired-goons.net/lights has some more info, though is
wildly out
: of date.
:
: --
: Dave Hughes |
: Striker, listen, and you listen close: flying a plane is no
different
: than riding a bicycle just a lot harder to put baseball cards in
the
: spokes.
:
:
:

"Travis" wrote in message
ups.com...
I'm thinking of making a DIY halogen bike light, I've seen a few web
pages on them and it looks like they're neither difficult nor expensive
to make, the biggest cost is the battery and recharger.

Places like Dick Smith sell 12V halogen globes for just a few bucks,
and I'm considering a 20W light system. I've got a very old cheap
incandescent bike light which I can put a bright bulb into and run
wires out to an external battery pack hanging from my top tube or
handlebar stem.

A few years ago I did pretty much the same thing - mounted a standard 20W
halogen dichroic lamp on my mountain bike, except in my case I used a 12v
gel cell hung from the top tube. The battery was a common or garden 7Ah unit
as used in alarm panels etc. and cost about $17. It would have weighed quite
a bit more than the NiMH pack you are talking about, but my bike wasn't any
kind of high-performance thing so it really didn't matter.

It was very simple to set up, worked very well only needing charging about
once a week.

On Sat, 22 Apr 2006 11:01:31 +0000, Wilfred Kazoks wrote:

The last two Silicon Chip magazines www.siliconchip.com.au have featured a
circuit to drive up to 6W of Luxeon LED's.

Aaargh! Poo, I saw that on the front and didn't actually grab the issue.
Might have to buy the kit from Jaycar in a month's time. Thanks for the
heads up.

They made the claim that it is bright enough to
safely travel at 75kph, downhill of course.

During the day maybe. I reckon @ 75km/h you'd be outrunning an HID.
Hmm, The rec.bikes FAQ seems to indicate 5ms^-2 is a reasonable maximum
deceleration for a bike, and it'd be in the right ballpark. 75km/h is near
as spit to 20ms^-1, so it'll take around 4 seconds to stop.

Basic physics says the stopping distance is (4*20)-(0.5*5*4^2) =
80-40=40m. So you'd need a light that's got good light out to 40m - add
another 0.5s for reaction time, and that's 50m. Searching a few articles
on dansdata indicates you'd be doing well to see 25m by a 5W Luxeon, which
matches pretty closely to what I've observed using them.
--
Dave Hughes |
Strange things are afoot at the Circle-K.