Leisure Battery losing charge

[Marcowner]

Hi All

I'm having problems with my leisure battery and think it is dead but i want to get some advice. Here's the situation

Background:

• 2019 Marco Polo with new Leisure Battery in December 2024
• It was used throughout 2025 and kept the fridge powered for 3+ days (on fridge setting 3-4)
• It was last charged on the mains in September 2025
• It was then driven occasionally over the winter

The issue:

• In April 2026 (6-7 months after last mains charge) i couldn't revive the battery and nothing worked - fridge or pop-top
• Driving for many hours made no difference
• It took 24-36 hours of mains charging before it came to life
• But, now it barely powers the fridge for ~4 hours
• With the fridge off, i see that battery bars lit either end of the charge indicator (signifying no current draw) but even then the voltage drops over time

(Note: I have since learned about the recommendation to mains charge every month, but didn't know before)

Mercedes are encouraging me to pay a diagnostics fee, which is almost half the cost of the fitting a new battery. Could this be anything other than a broken battery? If this is the most likely problem i'll just go straight for a new battery

Thanks in advance