I had the switch on both while under way, but when I was stopped I had it on one. When I went to get back under way I switch it to both and that's when I got the slow crank. I also notice that while on one when I was sitting there wasn't enough in it to even run the radio, so I'm thinking I'd rather just replace both for peace of mind, just gotta figure out which group. Last thing I want is a battery issue out there.
2006 2200 SR3