I'm trying to convert non-chargeable mp3 players into charger and mp3 player at the same time so the user can simply plug the mp3 into any USB to charge his battery
To lower the cost of converting as much as possible my idea is to use a 2.4v zener diode (the device hold 2x AAA batteries) connected between the USB connector positive pin and the battery positive pole.
My question is since the device will try to charge the batteries constantly as long as it's connected to USB (5V - up to 500mhA) will that setup harm the batteries if left for a long period of time and is there any other options?
I'm thinking about using Ni-Ca batteries since Ni-Ca can endure overcharge better than Ni-Mh and Lithium
To lower the cost of converting as much as possible my idea is to use a 2.4v zener diode (the device hold 2x AAA batteries) connected between the USB connector positive pin and the battery positive pole.
My question is since the device will try to charge the batteries constantly as long as it's connected to USB (5V - up to 500mhA) will that setup harm the batteries if left for a long period of time and is there any other options?
I'm thinking about using Ni-Ca batteries since Ni-Ca can endure overcharge better than Ni-Mh and Lithium