I have a couple of tractor batteries that were purchased new 4-5 years ago and then the tractor was never used. They sat outside, went flat, and went through cold winters. Is it possible to recondition these to get them going? The local dealer wants about $600 for the pair, and this tractor only gets used a few weeks a year. If possible, I want to save the cost this year due to limited budget, right now I'm making some hard choices on what to keep and what to sell.