battery power and 12v lights...

[PaulS]

Ok, this is what i am doing,

i am making my own 12v lighting system to go on my bike (the human powered one) cause its dark in the morning when i go.

I want to use a 12V 20W 51 mm Halogen dichromic globe.

You can power these with an SLA battery but these are big and bulky.

So what i was thinking is using AA Ni-MH batteries. 2800 mAh.

So here is the question how many of these batteries would i need to get about 90 min run time?

Thanks
Paul

[Iain]

Theoretically you should get about 1.6hours if the batteries are full (10 batteries in series to produce 12v)
20 watts = 1.666666666 amps therefore 2.8 amp hours should give you about the above.
You would do better to double up with two banks of 10 series parallelled and give you a better run time but could be a bit of a sod come charging time.
At current prices that would be about $100 worth of batteries.
Would a little gel cell be a better option strapped on a carrier rack or under the saddle somewhere.

[bitingmidge]

Paul,

Don't reinvent the wheel, go to The Fat Hippy's Website for a complete rundown on making bike lights as you describe.

He's got the coolest, cheapest light design, using a chrome towball cover as a case all held together with stainless hose clamps, and a bit of a discussion on batteries too!

I've seen a few using burgler alarm batteries, strapped to the seat post like this: http://www.users.on.net/~fathers/alternative.htm. Have a poke around anyway!

Cheers,

P

[PaulS]

Thanks
Yes i have seen the fat hippy lights and was working on that design, just thought i could do an upgrade on the batteries. I found 16 AA Ni-MH batteries on ebay for $45 delivered.

Paul

[ptc]

We used to have dynamo's rubbing on the tyre

[Iain]

We used to have dynamo's rubbing on the tyre

Throwing out a blazing 5 watts of dimness as I recall from my youth, haven't seen them in a while.
I also remember my old bike, same steel as used in the Sydney Harbour Bridge, felt about the same weight too.

[ptc]

Mine was a Rudge.

[Iain]

Aaaaahhhggggg, I remember them, mine was a raleigh, and before that 'something' Miami 5 speed racer, real state of the art in the early 60's, and before that the old Sturmy Archer (3 speed) ball bearing gears (correct me on spelling if it's wrong)

[ptc]

Mine had the Sturmy Archer A leather sadle and sadle bag
The bike was Black.

[bitingmidge]

We used to have dynamo's rubbing on the tyre

And on the old Malvern Star, when I was about twelve, we had a hill near our place where if you pedalled at about 150rpm in top gear on the Sturmey Archer, you could blow the bulb on the headlight!


P

[RETIRED]

And on the old Malvern Star, when I was about twelve, we had a hill near our place where if you pedalled at about 150rpm in top gear on the Sturmey Archer, you could blow the bulb on the headlight!


P

Used to do that on hill near our place called Olivers Hill. Got booked once for doing 65 MPH instead of 35MPH going down there.

The magistrate gave me a warning.