DIY bike lights / AA battery current

Quoted post said:

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.

On 2006-04-22, Travis (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

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?

Quoted message said:

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"

Quoted message said:

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 [censored] 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 ?

Quoted message said:

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.

Quoted message said:

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

Travis said:

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.

Quoted message said:

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.

Quoted message said:

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 | [email hidden]
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.

TimC said:

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.

Quoted message said:

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 | [email hidden]
"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.[censored] smith
stores might sell Silicon Chip also.
Regards Wilfred

"Random Data" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Travis said:

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.

Quoted message said:

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.

Quoted message said:

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 | [email hidden]
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 [censored], just a
battery wires and a switch

"Wilfred Kazoks" <[email hidden]> wrote in message
news:[email hidden]...
: 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.[censored] smith
: stores might sell Silicon Chip also.
: Regards Wilfred
:
: "Random Data" <[email hidden]> wrote in message
: news:[email hidden]...
: > 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 | [email hidden]
: > 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" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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 [censored] 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.

Wilfred Kazoks said:

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.

Quoted message said:

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 | [email hidden]
Strange things are afoot at the Circle-K.

Random Data said:

As I said in my earlier post, but want to reinforce - you'll get serious
voltage sag. .

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 |r?"

Agree with all the voltage drop info. Would not muck about with halogen for road. Too much current (amps)
Go for 2 x 3 watt Luxeons, and 2.5 amp hour AA cells for just $5 each, the "spot" optics and a good waterproof switching setup from Altronics (1) or Jaycar (2). Oatley voltage regulator kit is tiny and simple to solder.
Silicon Chip Magazine has a super bike light project in current, and cont. next month. Its a bit "techo" to the point of stupid but some might like to carry an electronic anchor.

Or just opt out and buy something.
Some good prices here, Au$1 = NZ$1.10 and only $9 freight.
torpedo7.comlights accessoriesOpen ↗

If you are going to muck about with lights have a RELIABLE backup light with you until you sort out all the bugs. I found out why!

Have Fun
Hugh

Phil Allison said:

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

Maybe dazzling to a motorist ?

Generally you tend to aim the light down onto the road. Its main purpose
is to let you see where you are going {:-).

OTOH, I do run a 50 watt when I am on brightly lit streets with lots of
neon signs etc.

Quoted message said:

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.

I've done exactly the same. I saw just over 5 hours out of a fully
charged 7Ah, and that was when I really really needed it too while
touring. 🙂
("I won't need to find somewhere to sleep tonight-- it will only take
me a few more hours to reach home.." Oops. Make that a 1am finish..)

--
Chris

I run a 15W halogen headlight off 10 NiMH AAs which are taped in holders (4,
4, and 2) then wired together and then put in a 500ml water bottle. AAs off
eBay don't meet their rated capacity. I have some marked 2500mah but they
test out as around 1800-1900mah. The Eveready 2500mah AAs that you can buy
in Coles and Woolies are a true 2500mah.

"SomeGuy" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Quoted message said:

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.

Travis said:

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 [censored] 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

Travis it's easy to make up a good soldered battery pack.
I have two NiMh packs that I've made myself. One is about 2.5 amp hour
and the other is 4 amp hour, both rated at 12 volts using 10 cells in
each. I made them from Sony batterys but most brands are quite good now.
You have to get the ones with the tabs on the top, but be careful
because some have stainless steel tabs which you need to spot weld and
some have tinned tabs. The tinned tabs are the ones you want.
Lay 5 cells side by side oriented so that the positive of one end is
next to the negative of the other. To do the connections you have to
bend one of the tabs backwards against its original bend, and you may
have to trim off some of the tab but leave enough so they completely
overlap for the width of the end of the battery.
Now you get some fine sand paper or steel wool and give the tinned
surfaces a bit of a rub or else the solder won't stick to it properly,
they seem to leave some sort of coating on them at the factory.
Next apply some solder to the surfaces but don't solder them together yet.
Use good solder which has about 70% led and 30%tin which has the lowest
melting temperature. The secret to good soldering is to always keep
things clean. Clean the surfaces before you solder them, make sure the
soldering iron tip is clean and free of crud, wipe it on a cloth and
apply fresh solder to it before making each join. The active component
of the flux evaporates out of the solder very quickly leaving
accumulated crud which is why it's important to always wipe the tip and
apply fresh solder. (The flux is inside the solder.)
So now that you've tinned all the tabs, use electricians insulation tape
to bind the 5 cells together so they don't move. Carefully solder all
the tabs together. Because you've presoldered them you should only need
to push them together with the soldering iron and the solder already on
them should be adequate to make the joint. Wrap a heap more tape around
it to make it firmer.
Make a second pack of 5 the same way.
Now solder some wire to the the main positive and negative of each pack,
plus a short bit that joins the two packs in series. Allow longer length
than you think you'll need.
I use special flexible wire from Farnell or Radio Spares which is like
the wire used in multimeter leads, it has a lot of fine strands and
flexes without breaking. Don't use single strand wire, it won't last
long at all. Secondly, use red for positive and black for negative, that
way there is no mistakes.
Use the wire to join the two packs instead of the tabs so as to allow
for some flexibility of the pack if it gets jolted around on the bike.
Now that you've got it all together wrap a heap more tape around the
whole pack so every part of it has at least three layers of tape over
it. By now it should be a nice solid pack.
Now you need to put some connectors on it. The ones I use are from [censored]
Smiths, they are a whitish plastic and you can buy the pins separate
from the plug. I use the two pin plug, it's designed so that it will
only fit one way so you can't reverse the connections and blow things
up, as an extra precaution I have one male pin and one female pin in
each plug so there's no way I can get it wrong. My lights, chargers and
battery packs are all set up with this arrangement. I use LED lights
which are fed via a Luxeon current regulator which allows me to use
between 8 and 14 volts and I have two NiMh batterys and two Lithium Ion
batterys so I can swap between any of these batterys on my lights by
simply unplugging one and plugging in the other.
I wrap the battery in bubble wrap and push it into a cut off water
bottle which goes into the cage on my down tube. An important thing is
to remove the battery from the bubble wrap when you charge it as the
bubble wrap is a very good heat insulator and you'll cook your battery
if it goes into an overcharge state. Lithium Ion batterys are especially
susceptible to this. (I know from experience!)
I've been using my batteries for at least two years now without
problems, my two old Gel Cell batteries are unused in the shed. (Lead
acid batteries should always be stored in a charged condition, a flat
lead acid battery dies very quickly.)

A good charger is the MW1768 from Master Instruments.
http://www.master-instruments.com.au/browse/Model/MW7168.html

It needs a 12 volt supply which might be a problem but it has a meter in
it and will charge 12 to 14 volt packs which most chargers won't do.
Master Instruments also have some other good chargers that are worth
looking at.

Good riding

Friday

Random Data said:

Wilfred Kazoks said:

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.

Quoted message said:

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.

My mountain bike and road bike both have twin 5 watt luxeons.
The arrangment is excellent for the road, for mountain bike riding I
sometimes wish I had a bit more when doing screamingly fast technical
downhills, but for the other 95% of the time it's great and when I'm
doing easy stuff or slow uphills I turn one light off. They're super
reliable and my design is very light, I never remove them from the bike.

http://www.hyperactive.oz.nf/Lights3/Luxeon3.htm

Friday

Travis said:

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 [censored] 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.

the old ones are best, putting a 20W lamp in a small plastic case is asking
for problems.

Quoted message said:

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).

Quoted message said:

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

1.7A seems like a heavy drain on them. they'll not meet thair 20-hour
capacity at that rate.

try getting a datasheet from the makers of the cells you're looking at.

power tools seem to use sub-C size so that size may be cheeper and/or have
better high current performance..

Quoted message said:

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

I'd look at lead-acid, as it's much cheaper for the same charge capacity
but Christchurch is flat and I'd not be be lugging the thing up upteen hills
going there and back.

Quoted message said:

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

--

Bye.
Jasen

"Travis" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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.

Hi Travis,
check out the following link for a 12v 7.2Ah sealed lead acid battery and
charger for AU$35, I haven't seen both any cheaper. Go down the page to you
see the package of battery and charger.
http://www.oatleyelectronics.com/battery.html

Also, Jaycar is selling a 12v 7.2Ah sealed lead acid battery for under $20
at the moment.

"Jasen Betts"

Quoted message said:

Quoted message said:

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

1.7A seems like a heavy drain on them. they'll not meet thair 20-hour
capacity at that rate.

** NiMH cells give very close to full rated capacity over a 1 hour
discharge - only if discharged in less than half an hour will there be
significant loss of capacity. See:
http://sanyo.wslogic.com/pdf/pdfs/HR-3UR.pdf

Ni-Cd cells are even better in this regard giving full capacity even over a
4 minute discharge.

SLA batteries are not so good, their capacity drops alarmingly when
discharged in an hour or less.

Quoted message said:

try getting a datasheet from the makers of the cells you're looking at.

** Cos that slack kiwi [censored] Jasen is too lazy too look up data and see how
wrong the info he spews about is.

........ Phil