While battery backup sump pump systems play an important role in basement waterproofing, the battery itself that powers such systems is equally important, if not more. The best backup system in the world may be completely useless if the actual battery is one of poor quality.
AGM (Absorbed Glass Mat), no-maintenance batteries are the best battery for supplying DC currents to battery backup sump pump systems. Most large rechargeable batteries are lead-acid type, as opposed to NiCads, which are generally more expensive. The acid in a lead-acid type marine battery will generally contain 30% sulfuric acid at a full charge. Through my 22 plus years experience as a supplier of battery backup sump pump systems to contractors around the United States and Canada, the most effective battery is AGM – Absorption Glass Mat.
Most typical gelled batteries contain the combination of acid and silica gel. AGM batteries provide all the advantages that come with gelled batteries. They do not, however, exhibit the disadvantages of gel batteries. The acid in an AGM battery is contained by the fiberglass mat, and yet is still available for the battery’s plates, resulting in faster migration of acid. This gives the battery a higher rate of delivery and absorption of amperage. Most typical gelled batteries must be charged at a slower rate to prevent cell damage from excess gas.
AGM batteries can be charged at normal voltages, without the need to recalibrate, or purchase special chargers. There are no charge or discharge current limits. With AGM’s low internal resistance, the buildup of heat is almost non-existent, during normal and heavy charged and discharged currents. Other gelled batteries have the potential to lose capacity if overcharged due to voids developing in the gel.
With the AGM battery’s low self-discharge of one to three percent average per month, they are able to be stored for a longer period of time without charging versus other batteries. Even if discharged for more than 30 days, an AGM battery can be recharged to almost full capacity.
Through electrolysis, AGM batteries preserve water as they charge. This is possible because of the recombining of hydrogen and oxygen, thus converting to water while inside the battery. Water loss in other gelled batteries, especially in hotter climates, is quite common and often leads to the premature death of a battery after a few short years. With the AGM battery, water loss is not a problem, making it maintenance-free.
Because of the mounted plates, acid will not leak or spill from AGM batteries. Because the plates are packed tightly, they can withstand shock and vibration. AGM batteries are completely non-hazardous, making them a more viable (and cheaper) option for shipping.
When considering the purchase of a battery backup sump pump system, insisting that the pump uses an AGM battery would be the wisest choice in order to maximize the effectiveness of the sump pump.