Sarah, you’ll see the location of the ‘DIP switch’ on Page 8 of the User Manual. As Gàirnealair says, to access it you’ll need to take the cover off. This switch is referred to as ‘the Charging Line Selector’ at the top of the unit (with the cover removed). If it’s the CB516-3 model it should have three positions A, B and C, otherwise it’ll have just two positions marked A and B if it’s the earlier CB516 model. To be honest it looks like it’s going to be a challenge to access it. Hope that helps.
@Captain Quick Many thanks for the link to the CB516-3 manual. Where possible, I like to have PDFs of as many of these sort of documents as possible (never know when you're going to need them, and they don't take up much space on an iPad).
@sarah_86 - if you have not already dived [again] into the depths of the cupboard where the charger is hidden , please think about doing so:
When I bought my Birchover, one year old, minimal mileage, great condition, bla bla bla, it was quickly obvious that the Leisure Battery was knackered and would not hold a charge. No amount of Recon cycles with a Ctek charger made any difference so I assumed the previous owner had over-drained the battery and I had a new one fitted. Yes, I could have gone back to the dealer and made a fuss but it was simpler and quicker to fix it myself.
In the process I opened up "that cupboard" and had a look at the Split Charger. The DIP Switch that @Captain Quick has directed to you to was set in the wrong position (Lead Acid instead of AGM) which I think will have contributed to the battery problems. I'm not knocking Hillside - they build a damn good product, but it is assembled by people, and people make mistakes, get distracted, and things happen . . .