UPDATE: I decided not to go down this route in the end, as my OEM battery is 640CCA and the only dual purpose batteries available in my required size with similar CCA are AGM batteries. AGM is obviously better than wet cell (for CCA, number of cycles and possibly reserve capacity too) but also about double the cost. I have instead gone for decent wet cell SLI car batteries at £60 each, 64Ah and 640CCA. Since I'd also need new cams to do parking mode properly, the total cost would end up being quite silly. OP: Both of my cars could do with new batteries, one is more desperate than the other so I'd like to make a decision fairly soon and before winter really starts to hit us. I don't currently use a parking mode on either of my cameras but would like to have that option available in the future with a different cam. In my search for a new battery, I came across a category known as Dual Purpose batteries. Supposedly, they are kind of half way between a typical SLI (Starter Lights Ignition) battery and a deep cycle leisure battery. One that I've found in the 027 size that I require is here: http://www.batterymegastore.co.uk/varta-lfd60.html It has a 60ah rating matching normal SLI batteries in that size and the CCA is also comparable with most normal SLI batteries of that size. The only differences that I can see, is that it may tolerate heavier use, or in our cases, parking mode, better than a regular SLI battery. Just obviously not as well as a true deep cycle battery would, but then a deep cycle in the same size would be less likely to start a car in the dead of winter. It is also around the same price as a normal SLI. Here is a comparable SLI battery at the same shop by the same brand in the same 027 size: http://www.batterymegastore.co.uk/car-batteries/none-start-stop/varta-d24.html For 60-odd pound with a 4 year warranty I think there's worse things I could gamble my money on. However, I'm no battery expert so was wondering if anyone on here had greater knowledge as to how sensible of an idea this seems?