Li-ion charging

[Thistle]

Not strictly boaty but a similar situation on board is easy to imagine.

I have an LED bike light with a Li-ion battery and usually recharge it from the USB port on my computer. There's a LED which indicates state of charge: flashing red when charging and turns to green when the battery is fully charged. When it is green I've disconnected it and immediately reconnected it: it reverts to flashing red, ie charging, for 10+ minutes before indicating full charge again. What happens during those 10 minutes? Is the normal fully charged state, say, 90% and I'm topping up to nearer 100%? Or what??

 

[Refueler]

This sort of question is common amongst RC modellers because LiIon is the basis of the LiPo batterys that are flying / driving all those electric models today.

The LED sequence is controlled by a simple 'chip' that senses when voltage in vs voltage out is equal and basically very little flow. You disconnect and battery basically rests and if you plug it in again ... it will show charging again till that 'equilibrium' is reached again.

Its not a simple 90% and then top up a bit more ... what you would be doing is ... yes getting a slight bit more charge in ... maybe 1% or so ... but in reality its not worth it.

LiIon - two things to remember :

1. NEVER discharge to zero or over discharge. It seriously damages it.
2. Never over-charge or charge at higher than stated rates.

 

[Thistle]

Many thanks. A nice clear explanation.