A
Zetor 7045 have original a 140 Ah lead-acid battery and a 45 or 55 A generator.
If he drives less, the tractor starts well and he start the tractor not so often then 75 or 80 Ah lead-acid battery can also work. But for winter its better th have a litle bit more capacity so 95 or 110 Ah will be better when 140 Ah lead-acid battery is to price expensive for your project.