The basic concept when connecting in series is that you add the voltages of the batteries together, but the amp hour capacity remains the same. As in the diagram above, two 6 volt 4.5 ah batteries wired in seri. In theory, a 6 volt 5 Ah battery and a 12 volt 5 Ah battery connected in series will give a supply of 18 volts (6 volts + 12 volts) and 5 Ah. A 6 volt battery is often three 2 volt cells and a 12 volt battery is usually six 2 volt cells. Theref. In theory a 6 volt 3 Ah battery and a 6 volt 5 Ah battery connected in series would give a supply of 12 volts 3 Ah(the capacity of the weaker battery always restricts the circuit) and if you did so it would work and nothing would explode (t. As covered in the section Connecting batteries of different voltages in seriesabove, the greater the differences in either voltage or amp hour rating, the more the discharging and recharging is unbalanced and t. When connecting batteries in series, the general advice is to use batteries of the same ratings and the same make and model in order to minimize differences in exact voltage and amperage. Note, we say 'minimize', becau.