Have you ever wondered why your batteries in parallel seem to fail sooner than you would expect? When asked how to charge batteries in parallel people commonly reply connect the positive to positive and negative to negative. Yep, electrically speaking that works. But what if you have an RV, for example, and need to add 3 or 4 or 8 batteries in parallel? Do you continue to add to the string in a linear fashion (Figure 1)? Or is there a better way to set up and charge your RV batteries in parallel? I’m willing to bet the vast majority of RV and marine owners have never considered or made the connection between early battery failure and improper setup. This How to Charge Batteries in Parallel tutorial is designed to move you from ignorance and insanity (doing the same things over and over and expecting different results) to a point of knowledge and confidence. To achieve this result we will share a framework of information and illustrate the improper and proper method(s) to achieve balanced charging.