Thank you all for the information and advice.
I think most of the lower end ebikes, like I am getting, supply a 2a generic charger matched to the voltage rating of the battery.
Charging to 80% then becomes a bit of a choir having to keep an eye on it till the battery voltage reaches the proper range.
This is where a smart charger like the Luna would be very helpful me thinks. The ability to adjust the charging rate down to as low as 1a is also helpful.
I am still researching proper battery management and learning a lot.