[Cabnchassis]

Have you checked the fluid level or is it a maintenance free one?

Sometimes just topping them back off can greatly improve function if the fluid level hasn't been down long, doesn't always work but I've never seen an old battery that wasn't low on fluid anyway so you can't hurt anything. Batteries do last longer if you keep the electrolyte levels at their capacity and all at the same capacity. When you're buying cold weather batteries for a diesel every couple years it gets a lot easier to remember to check on that.

If it is low use only distilled water from the store or a distillation filter when you are adding water to car batteries.