So i bought my 06 Civic Hybrid with 90k miles on it, so far so good but it did have a interstate 51R battery in it that's about 4 years old and I took it up to work load tested it and it says 416 CCA tested Bad, so as with me working at a car shop I have some spare batteries laying around for other home projects(lawn mower generator). I put in a 5 year old Duralast Gold 51R that's testing 508 CCA Good but I know its old and will not last for long and looking into options of what others are running and what seems to be best. I know that the car doesn't really use the battery much but is needed to run correctly. I know that the car came with a 151R battery originally but mines was changed out. Now my big question is the 51R ok or is it better or worse than the 151R. I know the 151R has lower CCA than the 51R, weighs less too(not much). Will the DC to DC convertor struggle more to charge the larger 51R? Is it worth while to go with the Optima 51R(I don't sit running the electronics with he car off). So basically I'm asking to I need to just get the stock size 151R or Just go with the 51R?