Ctek is a Swedish company that makes car battery chargers(see my previous review of CTEK 5.0 polar). It also sells these comfort indicators, that are charging plugs with three led lights,
it shows red blinking led if the battery is below 12.4 volts.
It shows yellow led if the voltage is between 12.4-12.6 volts.
Above that it shows green. Fully charged battery should and could rest at this voltage, but it’s rare. This tricker happy behaviour causes the ‘comfort’ indicator to cause more discomfort than comfort. As in normal winter the comfort indicator shows only red. I think the green should show anywhere above 12.4 volts, yellow from 12.1 – > 12.4, and red below it.
Here’s demonstration installation to Toyota Avensis.
Try to stay warm, it’s kinda cold up here…-JP