Can Dynamo Charge Battery?

[m3gsi]

You need about 8 volts from the dynamo.
        1n4001          Vin  ____ vout      1n4001
d-----anode/cathode-|-------|7805|-------anode/cathode
y                 +            |gnd                   +
n               4700uf         1k variable            6v
a                25v          resistor                sla
m                 -             |                      -
o------------------|-----------------------------------

Should cost about £3 to make adjust the 1k variable until you get around 6.7 volts output .  You need about 8 to 24v from the dynamo.
I make lots of sla chargers all the time.
m3gsi.

[tynevalleycommuter]

I've been wondering about doing exactly the same thing - charging Smart 10W/2.4W with 6V 4.5Ah from a dynamo of some kind. I have the lights and they have served me well for the last couple of years, but depending on weather conditions the capacity can be marginal for my return commute. I have tried using along with a small smart halogen front on rechargable AA's which I use to be seen or if the Smart set dies, but it's a lot of fiddling around recharging batteries. This year I have with been toying with either keeping a second charger at work to recharge the battery during the day or using a dynamo (bottle or spindle fitting)to keep the charge up or as a back-up if the batteries die. So my question is - has anybody made any progress in getting this to work since the last post in July? If so, I'd be very interested to find out how and any pitfalls! Thanks

[Stijn]

I didn’t realize this thread had been going on. I’ve looked into the “on bike power” question before, but couldn’t find a satisfying answer at the time. In the past I went for a more minimalist approach with a high capacity set of Ni-MH AA’s and a 110/220AC power socket charger and all my appliances being energy efficient, so I could get away with weeks without power socket.

I soldered up  a Luxeon LED front light about a year ago, which is plenty for me to cycle by at night. Now these are becoming commercially available. Cateye makes one and Exposure Lights, makes an awesome light which uses 2x 5Watt Luxeon’s.

However, a laptop was out of my league. It is now starting to make more sense to me, to use solar panels as supposed to a dynamo, since flexible panels have become much more affordable. The Coleman Exponent Flex 5 (5watt)  looks ideal for about £70, works even if your standing still, and zero drag. But less good when its cloudy. L

Mark McLean’s multi charger looks the business. Unfortunately I haven’t got the skill to put one together though. So who’s going to produce these for the cycling community?

I’ll be following this development with interest.

Cheers,

Stijn

[ahconway]

The Dec 2004 issue of What Mountain Bike? magazine features two gadgets that do this... there's the Coleman Folding Solar Panel (see http://www.ipcsolar.com) and a special friction dynamo (see http://www.cat.org.uk - go to the shop and search for "pedal").

The solar panel seems a little less practical and is a bit expensive at £90... The latter is only £20! Both send power to a cigarette lighter socket, so any mobile should be able to be charged with them. The dynamo seems an essential accessory for Thorn owners who have dynamo braze-ons but use battery-powered lights!

[scott1981]

Hi, I don't know what's the actual status on this thread but I've come up with a solution to the question posed here. I'm using a Shimano Nexus Inter L and a 6V 4 Ah SLA battery. I'm not sure that the alternator has a built in rectifier, this can be checked by measuring the output voltage with a DC voltage meter and you'll see the needle going left and right, or is using an LCD meter, you'll see the minus sign appearing and dissapearing as you spin the weel. So I did my own rectifier with a 1A bridge and a 4700 uF capacitor. The device has a switch which allows two functions 1) The alternator charges up the battery at a max current of 300/350 mA (limited only by alternator and circuit voltage drops), at a speed of 18km/h the charging current is around 250 mA and at 25km/h the charging current is around 300 mA. 2) The switch can me moved to this position to put the battery in paralell with the load, which in my case it's a Luxeon LED that draws around 250/300 mA (it's electronically limited). The alternator is capable of feeding the load up to 300 mA and the rest of the job is done by the battery. When you stop the battery does the whole job.

It would be a little bit difficult to explain the circuit design using just words here, but one thing I can definitely say is that putting a rectified signal in paralell with the battery is a inefficient way of charging it because the battery's internal resistance to charge would require a higher voltage to get a decent charging current than the one the alternator can provide. This was the model I used at the beginning anyway. You could easily get between 200/300 mA the the rpm had to be much higher than those needed to get the same current with the newer design. The solution I've come up with is using a NPN transistor whose collector is plugged to the negative pole of the battery, and the battery is plugged to Vcc in turn. then the emmiter is connected to a resistor that mirrors a reference voltage (eg 0.3 / 0.6 V for schottky or regular diode). This circuit tends to "force" a current into the battery in order to charge it regardless of the input voltage, obviously within certain limits like alternator max current and output voltage. It's a rather constant current design than a contant voltage design. SLA' should be charged with constant voltage, but taking into account that the riding time is not too much, this should not be a problem. However a comparator can be added to shut down the charge in case it goes above 7.0 or 6.9 volts.

If anyone is interested in this circuit, please email me at scott1981ar@yahoo.com.ar


Thanks and I hope to get in contact with someone here.

[scott1981]

Hi, I don't know what's the actual status on this thread but I've come up with a solution to the question posed here. I'm using a Shimano Nexus Inter L and a 6V 4 Ah SLA battery. I'm not sure that the alternator has a built in rectifier, this can be checked by measuring the output voltage with a DC voltage meter and you'll see the needle going left and right, or is using an LCD meter, you'll see the minus sign appearing and dissapearing as you spin the weel. So I did my own rectifier with a 1A bridge and a 4700 uF capacitor. The device has a switch which allows two functions 1) The alternator charges up the battery at a max current of 300/350 mA (limited only by alternator and circuit voltage drops), at a speed of 18km/h the charging current is around 250 mA and at 25km/h the charging current is around 300 mA. 2) The switch can me moved to this position to put the battery in paralell with the load, which in my case it's a Luxeon LED that draws around 250/300 mA (it's electronically limited). The alternator is capable of feeding the load up to 300 mA and the rest of the job is done by the battery. When you stop the battery does the whole job.

It would be a little bit difficult to explain the circuit design using just words here, but one thing I can definitely say is that putting a rectified signal in paralell with the battery is a inefficient way of charging it because the battery's internal resistance to charge would require a higher voltage to get a decent charging current than the one the alternator can provide. This was the model I used at the beginning anyway. You could easily get between 200/300 mA the the rpm had to be much higher than those needed to get the same current with the newer design. The solution I've come up with is using a NPN transistor whose collector is plugged to the negative pole of the battery, and the battery is plugged to Vcc in turn. then the emmiter is connected to a resistor that mirrors a reference voltage (eg 0.3 / 0.6 V for schottky or regular diode). This circuit tends to "force" a current into the battery in order to charge it regardless of the input voltage, obviously within certain limits like alternator max current and output voltage. It's a rather constant current design than a contant voltage design. SLA' should be charged with constant voltage, but taking into account that the riding time is not too much, this should not be a problem. However a comparator can be added to shut down the charge in case it goes above 7.0 or 6.9 volts.

If anyone is interested in this circuit, please email me at scott1981ar@yahoo.com.ar


Thanks and I hope to get in contact with someone here.

[daviddd55]

quote:Originally posted by ahconway

The Dec 2004 issue of What Mountain Bike? magazine features two gadgets that do this... there's the Coleman Folding Solar Panel (see http://www.ipcsolar.com) and a special friction dynamo (see http://www.cat.org.uk - go to the shop and search for "pedal").

The solar panel seems a little less practical and is a bit expensive at £90... The latter is only £20! Both send power to a cigarette lighter socket, so any mobile should be able to be charged with them. The dynamo seems an essential accessory for Thorn owners who have dynamo braze-ons but use battery-powered lights!

Has anyone tried this gizmo yet?

[Smoothoperator]

I would also like to get sorted a 12v system, not just to run lights but to charge my lights mobile and GPS as I'm planning a sposored ride from southern Spain to London. Weight is going to be a crucial thing as it is as Im going to be carrying all my food with me as well as tent and sleeping bag towed behind on a trailer (This is going to be fun over the pyrenees mountains I can tell!)
I was thinking about a trickle charge system. I do know my old teacher at school was a whizz at electronics - He was also a pervert and took naked pictures of a load of kids including me. Maybe it's time to forgive and forget and bribe him into building me a system for free before I try to get the police to prosecute again?

[bryfos]

http://seoulp4bikelightshombrewed.blogspot.com/2007/05/my-requirements-re-touring-bicycle.html

My experience yes Shimano dynohub is great! click link for my doings re. independent power system on touring bike.
cheers bryfos[]

[chen2x18]

It should be the 75Ah car battery can shove a >200A surge through the starter motor. If your charging circuit & your alternator's rectifier are not man for the job & a fault occurs then you may see smoke coming out of the hub.


_________________
LED Flashlight

[freddered]

My B&M IXON IQ front light takes 4 x AA batteries.

The manual says there is a recharger adapater that utilises a dynamo.

1 - It's a superb front light
2 - It sounds like a simple solution if you need AA batteries topped up

[Danneaux]

Since this is a dated but frequently-viewed topic by guests, I suggest also searching using the terms "Battery-charging" and "Tout Terrain The Plug 2" (no quotes) under the "Lighting" category. Much of the later discussion about dynamo battery charging has taken place in those threads.

Best,

Dan.