Hi have an old solar floodlight I would like to redesign using 18650s and suitable circuitry.
The system used to have a 6v dry cell and a 8x6" solar panel to keep it charged. Unfortunately this was pretty useless - the cell would never retain a decent charge and eventually the control circuits died - now stripped from the unit, leaving me with a nice flood panel, an empty battery box and an external solar panel that generates 5 or 6v in good light (not measured current capability).
The LED panel has 80 LEDs. Hooking these up to a variable power supply shows they are pretty bright at around 4v drawing around 400mA. Wiring up a single 18650 gives a decent light brightness - with again a current draw of around 400mA.

I would like to hook up one or more 18650s (probably in parallel) with discharge and over-charge protection, charging them from the small solar panel.

Any ideas on what components to use would be appreciated.

 

http://www.ti.com/lsds/ti/power-management/energy-harvesting-solar-charging-products.page

Something there will fit your needs.

 

OK - decided to buy a Single Cell Lithium Battery Charging Board and (separately) a single cell lithium battery protection circuit from eBay - only a few pounds each. The charging board should regulate the voltage and current from the solar panel down to 4.2v and keep the 18650 topped up. The protection circuit will prevent over discharging.
I am guessing that these will also work with a few 18650s in parallel as well..
Just thinking about adding a new PIR to the mix to re-establish the original security functionality rather than a simple manual switch for use a simple floodlight.