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

 

[Roy C]

I would say it is a new battery required. Cold temperatures will degrade the (any) battery and hence the requirement to charge monthly over winter. Personally I’d take it to a car battery / tyre specialist and they’d be able to test the battery and tell you if it is defunct (and replace it, if needed) without the annoying diagnostics fee that Mercedes dealers always seem to charge.