auxiliary battery

[Rodders]

Good morning, my auxiliary battery is showing malfunction and drops down to around 8 volts when engine not running so I suppose its time for a new one. Van is Marco Polo camper 2018 with 30,000 miles. Can any let me know best place to buy one and what size and wattage to get. Thanks

 

[DogWagen]

Not had to replace one myself (yet!). There's a few threads on batteries if you search using "battery" which will help