Any USB port can supply 5V at up to 500mA. The USB standard specifies that a device may not use more than 100mA until it has negotiated the right to use 500mA, but apparently no USB ports enforce that requirement. This makes the USB port a convenient source of power for devices such as this charger.
USB AA NiMH and NiCd Battery Charger: [Link]
Mark: To keep the lights on and the camera going I have a multi-purpose battery charger. This contains around 24Wh of energy storage in eleven NiMh AA cells and circuitry to charge my laptop, satellite phone, mobile phone, camera battery and a PP3 for Ju’s Dog Dazer. It can also power a white LED tent light that sheds just about enough light to cook by. A cunning design means that some of the AA cells can be removed from the internal battery stack and exchanged with flat ones from a torch or whatever.
The battery stack can be charged from a DC supply of between 10 and 30V (which includes the laptop’s mains adapter) and from my Schmitt Dynohub and from a 5W solar panel. I seem to be able to generate about 8Wh from a day’s pedaling, which is supplemented by whatever the solar panel can gather.
It seems that from a typical day of pedaling and weak sunshine I can garner enough power to run the laptop for about an hour. I try to keep the laptop’s battery fully charged so that the power from the charger goes straight into doing something useful in the computer. It is of course possible to use it to charge the laptop’s internal battery but this is less efficient because it involves an extra two conversions between chemical and electrical energy.
Multi-purpose charger: [Link]
The following project could prove very useful for those of you who are into robotics, because as you may know robotics uses lots of batteries and needs to charge them fast, so the bots can be up&running again. The authors states that this battery charger charges a NIMH 5-pack battery used in the BiPed robot in less than 1 hour, and charges the 10-pack NiCd used in the Snuf robot in about 30 minutes which i think is more than ok for a DIY project.
To prevent overheating of the battery, the charging current is turned off when the slope of the battery-voltage turns from positive into negative. A second termination-criterion of the charging process is provided for safety: the charge time is limited to about 1 hour.
Rapid NiMH / NiCd Battery charger: [Link]
As you may have noticed commercial NiCd/NiMH battery charger’s are not that efficient when it comes to charging time. There might be some expensive models but we are not referring to that. So Peter Hayles, the author of this project decided to build its own efficient NiCd/NiMH battery charger. He says that with the DIY charger he managed to cut the charging time from 4 hours to 1.5 hours max. This sound good to me.
Efficient NiCd/NiMH Battery Charger : [Link]