Need help finding a 2S 12v charger

A few months ago I built a small portable cross band radio repeater based on a wouxun kg-uv8d powered by a 2s4p 18650 pack for use on search and rescue missions. At the time I thought a turnigy 2/3s 12v charger would be perfect, but it never fully charges the batteries and sometimes randomly decides to stop charging.
I’m looking for something that can balance charge 2s4p in a reasonable amount of time from 12 volts (this is critical) just by plugging it in. I don’t mind using a hobby charger when I use it, but I want it to be plug and go for other less technically inclined people on searches. Ideally it should have low parasitic drain since it will stay plugged in to the batteries.

- IF the pack is really 2 series and 4 parallel, then it’s only a 8.4V max!!

12Volts into 2s Li-ion will result in venting, fires, or potentially an explosion. -

EDIT: I think you meant 12VDC input to the charger? In that case your safe and I don’t know of any chargers that meet those requirements at this time.

Yes, I meant 12v into the charger