The basic concept is that when connecting in parallel, you add the amp hour ratings of the batteries together, but the voltage remains the same. For example: 1. two 6 volt 4.5 Ah batteries wired. This is the big “no go area”. The battery with the higher voltage will attempt to charge the battery with the lower voltage to create a balance in the. This is possible and won't cause any major issues, but it is important to note some potential issues: 1. Check your battery chemistries – Sealed Lead Acid batteries for example have different charge points than flooded lead acid units. This means that if recharging the two.