RND Power Solutions High-Efficiency Solar Powered Battery Charger can recharge 4 AA or 2 AAA Ni-MH / Ni-Cd batteries by USB adapter or solar charge. We incorporate an extended design where you can connect with extended solar panels for a quicker recharge (sold separately). Use 4 AA Ni-MH batteries (above 2000mAh) as back up battery to charge your smartphone MP3 Player GPS and other USB charged devices. Our charger comes with holder that is suitable for the iPad iPhone and other smartphones. We included 4 channels for independent charging in order to protect each battery. Each channel has an indicator to show the status of each battery.