When is it charged?

Discussion on a forum yielded the idea that charging can continue (at least on some systems) after the charging lamp changes from Red to Green. This blog post serves to show that it can and probably does.

As it happens I have an inline meter which measures this sort of thing (as well as accumulates a bit of data such as peaks and averages) and is sensitive to 0.01Amps over quite a voltage range. I bought it for working with Solar charging systems (and its appeared in a few videos before). I'd adapted it to plug inline with my Mercane charger and allow me to monitor the charge.

It charges quite solidly at about 2 Amps, then towards the end falls off. Like this:

You can see a small taper off in voltage and it still draws an amount until it eventually falls to 0.00V

So lets look at the phases of charging (meaning what happens over time) for a normal lithium cell. Its divided into constant current (where the cell soaks up all the amps its given) and then a drop in current signals that the battery is filling up (as the cell starts to fill up like a baby not wanting more) and that amps going into the battery represents the charging (which it does see here).

You can see that there are only small changes in V note my red annotation lines up until the battery starts to slow down accepting more electrons (and Charge current drops). Yet it takes nearly another 2 hours before the battery is at 100% capacity. Its at this time that the BMS starts distributing incoming power to the other cells.

Having some understanding about how many BMS work, this is consistent with the "distribution phase" where power is distributed to the lower cells (often from adjacent cells also being topped up by the BMS) until (*I assume) the cells are all at 4.2V or the BMS gives up and declares there is not enough current moving and the cells are as balanced as they're going to get.

In the video (segment) of my charging below you can see the moment when the light went to green, and then the 150A reported a drop in amps being drawn to under 0.3A

Which shows that it may not actually be finished charging when the light has gone green, as current is still being drawn for some time. Without a meter (like this one) there is really no way to know (unless your scooter has some fancy firmware that monitors charge) what your batterys behaviour is.

I believe that this implies that the green light on the charger is switched from Red to Green when the amps drawn from the charger falls below a threshold, however charging may still be taking place.

So for those who are "worried" about the battery being "killed" on the charger, I recommend strongly that you consider giving it a full on the charger overnight charge at least now and then (perhaps every second charge). I think its silly to worry about this, because its only the leaving of the battery at over 4.2V for significant durations that causes any (minor) harm to the battery. I'd say that mine only stays at 4.2V for the small amount of time between full charge and usage commencement 

... may as well go out for a ride eh?