If, when you find your mains charger, you find it is a Christec, the chances are that it is old enough for the charger to be end of life.
If you are contemplating replacing the charger there are excellent smart battery chargers out there.
It is also like that you have a split charge diode. If you have I’d recommend fitting a DC-DC charger for charging from your engine. It will transform your battery charge management situation