Absorbed Glass Mat (AGM) batteries are constructed of lead plates packed between silica-glass mats that hold electrolyte in suspension. Because the electrolyte is sealed inside, water does not evaporate and this eliminates the need to add distilled water to the cells as is required with liquid lead acid batteries. AGM batteries are durable to withstand severe vibration, shock, freeze damage and accelerated charging.

Continually discharging the battery bank 100% will shorten battery life. Batteries have a limited number of life cycles to recharge. The life cycle is extended in AGM batteries, commonly up to 1000 cycles at 50% discharge level (liquid lead acid batteries average 500 cycles at 50% discharge level). To gain the maximum use out of AGM batteries it is important to avoid discharging the house batteries below 50% state of charge.

Cost for AGM batteries is generally higher than liquid lead acid and may be an upgrade you want to consider if you plan on using your current motor home for another five years. If maintaining liquid lead acid batteries is difficult to fit into your upkeep schedule, AGM batteries can help reduce the amount of time you need to spend attending to the RV battery bank.

A few routine maintenance items will need to be performed on the AGM batteries. Wash off the top of the battery cases once per month to remove dust and grime. Check that the cables are secure and if the cables require tightening torque to 70 in. lbs. Do not mix AGM batteries with liquid lead acid as charge and discharge characteristics differ. Keep the same type batteries on a single bank for consistency.

AGM batteries are most likely to suffer due to overcharging. Use a digital DC Volt Meter to monitor the battery state of charge (SOC). Test the SOC with the cables disconnected after the batteries have been at rest for at least one hour. The following chart outlines voltage readings:

100% SOC 12.80 Volts or greater

75% SOC 12.55 Volts

50% SOC 12.20 Volts

25% SOC 11.75 Volts

0% SOC 10.50 Volts

Remember, you can extend the life of AGM batteries by preventing the state of charge from falling below 50%.

Always fully charge the battery bank prior to placing the RV into storage. If the RV is not plugged into shore power during storage, disconnect the negative battery cable to reduce a draw on the batteries. The battery will still discharge when not in use. Recharge the battery bank every 90 days, even when the RV is in storage.