a properly exercised set shouldn't need one of these chargers. I have lawnmower batteries in my set and only exercise it every 4-6 months. I guess if you have a pair of $200 optimum batteries then a $40 solar charger is cheap insurance on not ending up with a destroyed battery. for me car batteries aren't even worth it. I have $50 into both batteries but I also have many deep cycle batteries laying around that are known good.
Whatever works for you.
Any battery sitting for that long will lose some charge and will suffer from some degree of sulfation.
That’s guaranteed
I will not risk my battery’s not being ready when I need them the most.
Have Solargizers on everything not close to power.
Battery Tenders on rest.
I do have red top Optimas in all my civilian vehicles and equipment.
Hawkers in all my MVs (except NF2D, have Red Tops)
I spend the $$ to make sure they are all properly maintained.
Like I said, you get what you pay for.
Buy something you “think” will work, only to find out later it fried/degraded the battery.
The extra $$ spent on a Solargizer/Battery Tender will save time and money in the long run.
Especially if, the save money set, made you have to buy a new battery.
Me......I’ll stick with what I know for a fact works.