The OEM batts. were replaced before I bought my truck, so I don't know or not if they are Maintainance free or not. If you can check the water level, they may need some, and clean the terminals if needed. It can make a world of difference. If they haven't been maintained properly, they're probably shot.
The guy that I bought my truck from put some cheap ones in it before seling it to me a little over 2yrs ago. I've taken care of them, but will need to replace them before too long for the same reason. No longer have the guts to start it below 15* or so if I didn't have it plugged at work.
My boss has a 1840 Case skid loader. Has the original battery in it yet (6+yrs). Just keep the terminals clean and add water when needed. I use anti-seize on the terminals instead of die-electric grease. It lasts much longer and does a better job.