The lights while it is plugged in indicate that the battery is charging https://www.dyson.com/support/journey/troubleshooting/164545-01.html#SV10%20VISUAL%20ISSUE,SV10%20LIGHTS,SV10%20CHARGER%20LIGHTS%20MENU,SV10%20CHARGING%20NEARLY%20FULL
The light while it is unplugged indicates the battery needs to be charged https://www.dyson.com/support/journey/troubleshooting/164545-01.html#SV10%20VISUAL%20ISSUE,SV10%20LIGHTS,SV10%20LIGHTS%20WHEN%20IN%20USE,SV10%20BATTERY%20NEEDS%20CHARGING
If the battery indicates a full charge while plugged in but immediately goes dead while unplugged, the battery has failed and should be replaced.