Ah (amp-hour) is your battery capacity. Bigger Ah means more stored energy and longer charging time.
Use your charger or solar charge controller output current in amps (A), for example 20A, 40A, or 60A.
SOC means State of Charge (your battery level now). 20% means mostly empty, 80% means mostly full.
This calculator estimates how many hours it takes to recharge your battery from a given charging current, whether the power comes from solar panels, a charge controller, or a mains charger. It helps you plan whether your panels and controller can refill the bank during a single day of sunlight.
It works from your battery's amp-hours and its current state of charge: it figures out how much capacity is missing, then divides by your charging current, with a 95% efficiency factor applied because some energy is always lost as heat during charging. A battery that's half empty charges in roughly half the time of an empty one, and a higher charging amperage refills it faster — though your charge controller and battery chemistry set safe limits on how fast you should push it.
Use this alongside the Solar Panel calculator: one tells you the panel wattage you need, this one tells you how long that array will take to top up the battery.
Common questions about how long a battery takes to charge.
Take the missing capacity (amp-hours still needed), divide by your charging current, and allow for about 95% efficiency. A 100Ah battery at 50% charged needs ~50Ah; at 20A that's roughly 50 ÷ (20 × 0.95) ≈ 2.6 hours.
Some energy is always lost as heat in the battery and wiring during charging. The calculator applies a 95% efficiency factor so the estimate reflects real-world charge times rather than an idealized figure.
Yes, up to the safe limit set by your battery and charge controller. Higher current shortens charge time, but exceeding the recommended charge rate can overheat or damage the battery, so stay within the manufacturer's spec.
Use the Solar Panel Required calculator to find the array wattage that refills your battery within your daily peak sun hours.
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