Tricky Project for Battery Charging Using Dynamo

This might be a good start: http://www.amazon.com/Generator-12V-Bicycle-Light-Power/dp/B000OBWMGK

Hi nabz,

I found some stuff HERE.

The normal bicycle dynamo of 6v ac will if rectified to dc using fullwave diode bridge charge a battery pack of NiMH 4.8v- However Li-ion or Li-po CELL of 3v7 needs special care in charging to avoid eruption-with-flame!!!. Basically it is a regulated charge at no more than 4.2v-amperage is also controlled.

See the manufatacturers information that will help you charge your NiMH batteries.

CHARGING.

NiMH Charge curve

The charging voltage is in the range of 1.4–1.6 V/cell. A fully charged cell measures 1.4–1.45 V (unloaded), and supplies a nominal average 1.25 V/cell during discharge, down to about 1.0–1.1 V/cell (further discharge may cause permanent damage, and the risk is increased with multi-cell packs). This voltage varies depending on the discharge rate of the cell (lower discharge loads result in an increased voltage output for longer periods, approaching the 1.4 V unloaded cell voltage). In general, a constant-voltage charging method cannot be used for automatic charging. When fast-charging, it is advisable to charge the NiMH cells with a smart battery charger to avoid overcharging, which can damage cells and cause dangerous conditions. A NiCd charger should not be used as an automatic substitute for a NiMH charger.^[7]

[edit] ΔV charging method

According to Panasonic and other NiMH cell manufacturers, the ΔV method is one of the preferred charging methods for charging. The charger measures the rate of change (signified by the symbol Δ) of the voltage of the cell (signified by the letter V). This is illustrated in the "NiMH charge curve" figure. The cell or battery is rapidly charged at a constant current of 1 C/h, where C is the capacity of the battery (the capacity is expressed in ampere hours, or more commonly milliampere hours (mA·h). After the cell is fully charged, and as it begins to overcharge, the voltage polarity of the electrodes inside the battery will begin to reverse, and this will cause the battery voltage to decrease slightly. A ΔV type battery charger ends the charge cycle by switching off the charging current when it senses this drop in voltage. In some cases, a very small "trickle charge" may remain. The "charge curve" graph also shows that the charge voltage will change depending on the charge current (it also changes with temperature and battery age). This generally means that a constant-voltage charging method cannot be used automatically, because it will either be unsafe, or it will not charge batteries reliably and consistently. This is unlike a lead-acid cell for example, which can, in theory, be more easily charged at a suitably chosen constant voltage.^[7]

Dickson.

See here: Battery Charger

http://www.instructables.com/id/Bike-that-charges-your-cell-phone-as-you-ride/