Your old charger is 56V max output voltage for Lead Acid. The new charger is 54.6V for Lithium battery. So doesn’t look like the right charger. It should have just under charged the battery. But as you say, maybe the 1.6A vs 2.5A output has burnt something out.
If I'm reading it correctly the pin orientation looks right. Maybe check with multimeter?
https://www.elektro2rad.de/product-719-723.html?language=en
“Description
ql-91435A-4801600F
This charger is suitable for 48V lead-acid batteries.
Technical specifications:
Brand QILI POWER
Model QL-91435A-4801600F
Input voltage AC input AC 240V 50Hz
Nominal voltage 48V
Charging voltage DC Output 56V
Max. Charging current 1.6A
Overload protection function Charger switches off or lights up green when the battery is fully charged
Operating temperature 0 ° C to 35 ° C
Connection output XLR plug
Weight approx. 400g
Connection input Mains plug for house socket
Connection output XLR plug
Polarity Pin1 + Pol / Pin3 - Pol”