Charging a Li-ion battery

Hi there, I am attempting to charge a Li-ion battery with a 10w 18v solar panel, however the charging requirement of the battery is 16v at 3.75A (think laptop battery!) so the 10W panel is insufficient to charge the battery even in direct sunlight.

I know the obvious answer is a bigger solar panel, however the appliance I would like to run off it is relatively low in power requirement (4.5v at 1.5A), so I wondered if there was an alternative solution

I had considered charging a smaller battery and linking it to the main battery on a timer such as the 10w panel would charge the small battery, the timer would trip and then then the main battery would draw its power requirement. Cycle ad infinitum....

Would this be a viable solution or could I use some kind of capacitance circuit to achieve this end???? anything you could suggest would be handy.

Many thanks, Raymond.

YOu do not need a specific current to charge a battery with. What you do need is a sufficiently high voltage get electrons to flow into the battery. IF the voltage level is high enough already, you can charge at the lower current level...it will just take longer. If the voltage is not high enough, you will need a switching regulator to "step up" the voltage.

That said, you do realize that lithium ion batteries can explode if overcharged, or it they become overheated during charging. You will need some sort of circuitry to sense what is going on in the battery, and keep it from exploding.

interesting... in that case I may discharge the battery and time how long it takes to recharge on my existing panel and make my calculations accordingly...

Te battery has over charge /discharge protection built in, thats why I chose it... I lack the knowledge to nigger rig my own circuit...

cheers