A deep-cycle AGM battery is the best choice for most backup sump pump systems because it handles repeated charge-discharge cycles without degrading the way a standard automotive battery does. LiFePO4 is the premium alternative if longevity and weight matter more than upfront cost.

Deep-cycle batteries are built to discharge slowly and recharge fully, which matches exactly how a sump backup system operates — sitting at full charge for weeks, then running a pump through a multi-hour outage. Standard car batteries are designed for short, high-current cranking bursts and fail quickly in this application. AGM deep-cycle batteries are widely available at home improvement stores and pair with the built-in 25A charger on inverter-charger units like the VIOPUMPO 2000W and 2500W sump backup systems.

  • Required battery type: deep-cycle AGM or deep-cycle lithium (LiFePO4) — standard automotive batteries are not suitable.
  • VIOPUMPO sump backup systems support AGM and deep-cycle lithium batteries via a built-in 25A charger with overcharge protection.
  • Estimated runtime example: a 100Ah AGM battery can run a 500W sump pump approximately 2–2.5 hours of continuous pumping.
  • Battery is not included with inverter-charger sump backup units and must be purchased separately.
  • LiFePO4 batteries offer longer cycle life than AGM but carry a higher upfront cost; AGM is the lower-cost, widely stocked option.

How to Choose

  • Pick AGM deep-cycle if: you want a lower upfront cost, easy availability at home improvement stores, and straightforward compatibility with the VIOPUMPO 2000W or 2500W built-in 25A charger.
  • Pick LiFePO4 deep-cycle if: you need a lighter battery, expect frequent outages that demand more charge-discharge cycles, and can absorb the higher upfront cost.
  • Pick a larger Ah capacity (100Ah+) if: your pump cycles more than once every 20 minutes during storms, or you need more than 2 hours of continuous runtime per outage.
  • Pick a smaller Ah capacity (55–75Ah) if: your basement floods rarely, space in the utility room is tight, and you want to minimize battery weight and cost.
  • Avoid standard automotive batteries if: the unit will sit on standby for weeks between uses — car batteries degrade rapidly under slow-discharge, deep-cycle conditions.