Q for deep cycle battery experts

Deep Cycle batteries are not all the same. Having owned a Large Marina and RV park over 25 years, and selling and installing solar and Batteries, I only used high quality AGM batteries, like "Lifeline" and others. The typical RV convertor is normally locked at 13.1 volts DC. Some newer ones are converters and chargers. A Deep Cycle Battery will only be fully charged at 14.4 volts. No more or less. This is the voltage that creates the chemical change on the plates. If you do not reach this voltage, you will not fully charge the Battery. I always use a meter to double check this important issue. Sometimes the voltage will rise a lot higher when charging. This means the battery is done and it has a dead cell. Avoid 6 volt series wired battery banks. Use 12 volt banks for the best performance. We find most 6 volt batteries have different resistance with the same brand batteries. Poor charging and short battery life. For example, our AGM batteries will last 10-15 years if properly charged and used. Never drain a battery completely. If you do, plan on replacing it soon. Any electrical-battery-solar questions, please ask!