tedbear - 1/10/2018 16:41

The suggestions are correct. On a modern tractor with 2-6 volt batteries they will be wired in series as the above drawing shows. By connecting them together in series, the voltage (pressure) is increased so the system is equivalent to a large battery.

This is what is really done internally in a battery, each cell is around 2+ volts so in a 6 volt battery 3 cells are connected in series internally. So with 3 cells in series the output is 6+ volts. If 6 cells are connected together in the battery the output wold be 6 x 2+ Volts or around 12 volts. This is why older battery types that had caps would have 3 caps for a 6 volt and 6 caps for a 12 volt.

To charge the above tractor with a battery charge, one would likely set it for 12V and put the clamps on the + terminal of the left battery and the - terminal of the right battery. Since the right battery goes to the frame ground, the idea of using the frame or step on the left side for the negative clamp is equivalent.

With that being said, I thought the Deere 50 series used 2-12 Volt batteries in parallel. If so, connecting to the + terminal on the left battery and the - terminal of the right battery would still be fine because the positives and negatives are tied together anyway.