What is deep cycle marine battery Amp-Hour Capacity ?

    Deep cycle batteries are rated in amp-hours. It indicates that the total amount of energy delivers at a constant rate of discharge over a period of 20 hours before it reaches a dead voltage. It is amps x hours. If you have a motor that pulls constant 20 amps, and you use it for 30 minutes, then the amp-hours used would be 20 (amps) x0 .5 (hours)=10 AH. A 100 amp-hour, 12V deep cycle battery will run a 10 amp-motor for 10 hours (100 amp-hours /10 amp =10 hours).

    The generally accepted AH rating time period for batteries is the "20 hour rate". This means that it is discharged down to 10.5 volts over a 20 hour period while the total actual amp-hours it supplies is measured. (A 12v deep cycle battery is actually "dead" at 10.5v.When fully charged, it will show 12.6v or more.) Sometimes ratings at the 6 hour rate and 100 hour rate and they are for different applications. The 6-hour rate is often used for industrial batteries. Sometimes the 100 hour rate is given just to make the battery look better than it really is, but it is also useful for figuring battery capacity for long-term backup amp-hour requirements.