I use a lead acid battery to power my bicycle lights. It is 6v & needs
replacing (it is only working for 45 mins now instead of hours).

I have been pondering using a 6v Dynamo to put charge back in whilst I am
cycling.

Hi All,

I use a lead acid battery to power my bicycle lights. It is 6v & needs
replacing (it is only working for 45 mins now instead of hours).

I have been pondering using a 6v Dynamo to put charge back in whilst I am
cycling. Now would be a good time to test this as the battery is at the end
of it's life span & dos not matter if I kill it completly.

My questions are;

I am guessing as a dynamo is basically, a motor, I will need something to
stop electricity flowing back & powering the dynamo as a motor. I think for
this I need a Diode - is this correct, and if so, what type of Diode do I
need to ask for?

If I wire the dynamo to the battery in parrallel with the lights, If I have
the dynamo charging whilst the lights are switched on, what happens? I am
guessing this should not blow the bulbs in the same way an alternator is
charging a caar battery all the time (unless some sort of regulator is
involvd?)(6v rated) - is this correct?

ANy thoughts? Or is this a daft idea?

"Hake" <colinj.wood@ntlworld.com> wrote in message
news:FXCdh.2115$Qa6.1352@newsfe6-gui.ntli.net...

I use a lead acid battery to power my bicycle lights. It is 6v & needs
replacing (it is only working for 45 mins now instead of hours).

I have been pondering using a 6v Dynamo to put charge back in whilst I am
cycling.

You'll notice the drag.

IME you are better off with dry cells and a dirty DC recharger. You can
carry a couple of spare sets with little weight penalty.

It is doable within limits. Find out what voltage your dynamo
generates under load and no load - presumably you'd do some peddling
during the day and that could be used to recharge the battery.

Good solution if you are camping for months on end with your bike.

Dynamos output AC and the rectifier diodes you'd need to convert to DC
to charge the battery would prevent discharge. A switch or two on the
handlebar would give you some flexibility on whether to use battery or
dynamo - or you could just use a steering diode - dynamo voltage goes
lower than the battery and voltage flows from the battery to the lamp.

It can be made lots more complicated - but a switch(s) and diodes and
you're home free at little expense with good control of the system.

Now - while you're at it reduce the current demands of your lighting
system. Switch to leds if you can. I mounted 56 white LEDs under my
motorcycle headlight and it is more than enough at night for bicycle
speeds (50-75 feet) - uses a measly 3 watts and looks brighter than
the headlight in daytime - just doesn't have the same beam spread only
20 degrees. Headlight consumes 50 watts. Leds set me back $7 and the
resistors and potting compound works out to about 9-10 total for the
lamp.

Consider Nickel Metal Hydride rechargeable packs or Lithium also - may
be able to lower the weight some.

Finally if you haven't already bought a dynamo; consider an in-hub
one. The thingees that rub against the wheels add a lot more drag and
abrade the tires over time. The in-hub dynamos start producing
earlier and are current regulated to some extent (not good for battery
charging- but saves light bulbs on an all dynamo system) The friction
types will pop a bulb at over 15 mph.

In-hub dynamos cost, but are well worth it if you drive in the dark a
lot. Requires a new wheel or some new spokes and re stringing the
wheel. Since you would have some bucks invested in the front wheel
ditch the skewers and use rounded lock nuts so the wheel isn't stolen.

To get power from the dynamo to the battery the dynamo has to produce
enough voltage to overcome the diode drops point six volts or so plus
a few tenths of a volt over the resting battery voltage (6.3 volts for
lead acid - so figure 6.6 volts - more is better) which works out to
7.2 volts. - a 12 volt system will be more efficient at around (14.5
volts for charging)

I was writing to some guy in France awhile back who has an automatic
system for charging and lighting - he camps in the mountains and uses
the battery for lighting the way and reading at night.

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It is doable within limits. Find out what voltage your dynamo
generates under load and no load - presumably you'd do some peddling
during the day and that could be used to recharge the battery.

Good solution if you are camping for months on end with your bike.

Dynamos output AC and the rectifier diodes you'd need to convert to DC
to charge the battery would prevent discharge. A switch or two on the
handlebar would give you some flexibility on whether to use battery or
dynamo - or you could just use a steering diode - dynamo voltage goes
lower than the battery and voltage flows from the battery to the lamp.

It can be made lots more complicated - but a switch(s) and diodes and
you're home free at little expense with good control of the system.

Now - while you're at it reduce the current demands of your lighting
system. Switch to leds if you can. I mounted 56 white LEDs under my
motorcycle headlight and it is more than enough at night for bicycle
speeds (50-75 feet) - uses a measly 3 watts and looks brighter than
the headlight in daytime - just doesn't have the same beam spread only
20 degrees. Headlight consumes 50 watts. Leds set me back $7 and the
resistors and potting compound works out to about 9-10 total for the
lamp.

Consider Nickel Metal Hydride rechargeable packs or Lithium also - may
be able to lower the weight some.

Finally if you haven't already bought a dynamo; consider an in-hub
one. The thingees that rub against the wheels add a lot more drag and
abrade the tires over time. The in-hub dynamos start producing
earlier and are current regulated to some extent (not good for battery
charging- but saves light bulbs on an all dynamo system) The friction
types will pop a bulb at over 15 mph.

In-hub dynamos cost, but are well worth it if you drive in the dark a
lot. Requires a new wheel or some new spokes and re stringing the
wheel. Since you would have some bucks invested in the front wheel
ditch the skewers and use rounded lock nuts so the wheel isn't stolen.

To get power from the dynamo to the battery the dynamo has to produce
enough voltage to overcome the diode drops point six volts or so plus
a few tenths of a volt over the resting battery voltage (6.3 volts for
lead acid - so figure 6.6 volts - more is better) which works out to
7.2 volts. - a 12 volt system will be more efficient at around (14.5
volts for charging)

I was writing to some guy in France awhile back who has an automatic
system for charging and lighting - he camps in the mountains and uses
the battery for lighting the way and reading at night.

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Thanks for all the Ideas, I shall spend some time trying find and price
components - I like the Idea of a LED system, but I am in the UK &
generally, we are ripped of for electronic components - but i shall
investigate!

Its interesting to hear of the guy in France - thats the sort of thing I had
in mind, I just have to get a bit of knoweledge to acheive it.

TO further the Idea, when I have nothing better to do I d like to buy a
excersise bike, connect it to a a alternator from a car & attempt to use my
excersising to cpower lighting and other things in the home - I know its a
bit crazy & doesnt really save much, but it just sounds fun!

What's crazy? - makes a lot of sense to power the TV while watching

If I take the bike thing any further, I will post how I get a long, I havent
got as much time as I would like though!


Thanks very much for the pointers,

Good luck
cheers,

Hake

My questions are;

I am guessing as a dynamo is basically, a motor, I will need something to
stop electricity flowing back & powering the dynamo as a motor. I think for
this I need a Diode - is this correct, and if so, what type of Diode do I
need to ask for?
It is true that dynamo on cycle is AC type. So use a bridge

If I wire the dynamo to the battery in parrallel with the lights, If I have
the dynamo charging whilst the lights are switched on, what happens? I am
guessing this should not blow the bulbs in the same way an alternator is
charging a caar battery all the time (unless some sort of regulator is
involvd?)(6v rated) - is this correct?

ANy thoughts? Or is this a daft idea?
Hake
If U have lights on while charging then not much happens than U